Search

Bloom syndrome (BS) is a rare genetic disorder caused by biallelic inactivation of the BLM gene, which usually manifests in childhood by significant growth retardation, immune deficiency, characteristic skin lesions, cancer predisposition and other distinguishable disease features. To our knowledge, all prior instances of BS have been identified via intentional analysis of patients with clinical suspicion for this disease or DNA testing of members of affected pedigrees. We describe an incidental finding of BS, which occurred upon routine germline DNA analysis of consecutive breast cancer patients. The person with the biallelic pathogenic BLM c.1642C>T (p.Gln548Ter) variant remained clinically healthy for 38 years until she developed breast cancer. Detailed examination of this woman, which was carried out after the genetic diagnosis, revealed mild features of BS. A sister chromatid exchange (SCE) test confirmed the presence of this syndrome. The tumor exhibited triple-negative receptor status, a high proliferation rate, a low tumor mutation burden (TMB), and a moderate level of chromosomal instability (homologous recombination deficiency (HRD) score = 29). The patient showed normal tolerability to radiotherapy and several regimens of cytotoxic therapy. Thus, some BS patients may remain undiagnosed due to the mild phenotype of their disease. BLM should be incorporated in gene panels utilized for germline DNA testing of cancer patients., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Bloom syndrome (BS) is a rare autosomal recessive inherited disorder. Patients with BS have photosensitivity, telangiectatic facial erythema, and stunted growth. They usually have mild microcephaly, and distinctive facial features such as a narrow, slender face, micrognathism, and a prominent nose. Kostmann disease (KD) is a subgroup of severe congenital neutropenias. The diagnosis of severe congenital neutropenia is based on clinical symptoms, bone marrow findings, and genetic mutation. Here, we report a female patient with a triangular face, nasal prominence, and protruding ears presenting with recurrent infections and severe neutropenia. Molecular genetic testing revealed a compound heterozygous variant in the HCLS-1-associated protein X-1 gene [(c.130_131insA) p.(trp44*), c.430 dup(p.Val144fs)] and a new homozygous variant in Bloom Syndrome RecQ like helicase gene [c.2074+2T>C p.(?)]. She was diagnosed with both BS and KD. To the best of our knowledge, this is the first case of coexisting BS and KD in a patient ever reported., Competing Interests: The authors have no conflicts of interest to declare., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Bloom syndrome (BSyn) is an autosomal recessive disorder caused by variants in the BLM gene, which is involved in genome stability. Patients with BSyn present with poor growth, sun sensitivity, mild immunodeficiency, diabetes, and increased risk of cancer, most commonly leukemias. Interestingly, patients with BSyn do not have other signs of premature aging such as early, progressive hair loss and cataracts. We set out to determine epigenetic age in BSyn, which can be a better predictor of health and disease over chronological age. Our results show for the first time that patients with BSyn have evidence of accelerated epigenetic aging across several measures in blood lymphocytes, as compared to carriers. Additionally, homozygous Blm mice exhibit accelerated methylation age in multiple tissues, including brain, blood, kidney, heart, and skin, according to the brain methylation clock. Overall, we find that Bloom syndrome is associated with accelerated epigenetic aging effects in multiple tissues and more generally a strong effect on CpG methylation levels., (© 2023 The Authors. Aging Cell published by Anatomical Society and John Wiley & Sons Ltd.)

Pathogenic variants affecting the BLM gene are responsible for the manifestation of extremely rare cancer‑predisposing Bloom syndrome. The present study reports on a case of an infant with a congenital hypotrophy, short stature and abnormal facial appearance. Initially she was examined using a routine molecular diagnostic algorithm, including the cytogenetic analysis of her karyotype, microarray analysis and methylation‑specific MLPA, however, she remained undiagnosed on a molecular level. Therefore, she and her parents were enrolled in the project of trio‑based exome sequencing (ES) using Human Core Exome kit. She was revealed as a carrier of an extremely rare combination of causative sequence variants altering the BLM gene (NM_000057.4), c.1642C>T and c.2207_2212delinsTAGATTC in the compound heterozygosity, resulting in a diagnosis of Bloom syndrome. Simultaneously, a mosaic loss of heterozygosity of chromosome 11p was detected and then confirmed as a borderline imprinting center 1 hypermethylation on chromosome 11p15. The diagnosis of Bloom syndrome and mosaic copy‑number neutral loss of heterozygosity of chromosome 11p increases a lifetime risk to develop any types of malignancy. This case demonstrates the trio‑based ES as a complex approach for the molecular diagnostics of rare pediatric diseases.

Rothmund-Thomson syndrome, a heterogeneous genodermatosis with autosomal recessive hereditary pattern, is an uncommon cancer susceptibility genetic syndrome. To date, only 400 cases have been reported in the literature, and the severity of the features varies among individuals with the condition. Here, we describe a 55-year-old male who had been diagnosed with Bloom Syndrome during childhood due to the suggestive physical features such as short stature, chronic facial erythema, poikiloderma in face and extremities, microtia and microcephaly. However, the genetic test demonstrated that the patient carried two pathogenic variants resulting in compound heterozygous in the RECQL4 gene (c.2269C>T and c.2547_2548delGT). He subsequently developed a calcaneal osteosarcoma, which was successfully treated, and has currently been oncologic disease-free for 3 years., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Purpose: This study aimed to describe the spectrum of cancers observed in Bloom Syndrome and the observed survival and age of first cancer diagnosis in Bloom syndrome as these are not well-defined., Methods: Data from the Bloom Syndrome Registry (BSR) was used for this study. Cancer history, ages of first cancer diagnosis, and ages of death were compiled from the BSR and analyzed., Results: Among the 290 individuals in the BSR, 155 (53%) participants developed 251 malignant neoplasms; 100 (65%) were diagnosed with 1 malignancy, whereas the remaining 55 (35%) developed multiple malignancies. Of the 251 neoplasms, 83 (33%) were hematologic and 168 (67%) were solid tumors. Hematologic malignancies (leukemia and lymphoma) were more common than any of the solid tumors. The most commonly observed solid tumors were colorectal, breast, and oropharyngeal. The cumulative incidence of any malignancy by age 40 was 83%. The median survival for all participants in the BSR was 36.2 years. There were no significant differences in time to first cancer diagnosis or survival by genotype among the study participants., Conclusion: We describe the spectrum of cancers observed in Bloom syndrome and the observed survival and age of first cancer diagnosis in Bloom syndrome. We also highlight the significant differences in survival and age of diagnosis seen among different tumor types and genotypes., Competing Interests: Conflict of Interest The authors declare no conflicts of interest., (Copyright © 2022 American College of Medical Genetics and Genomics. Published by Elsevier Inc. All rights reserved.)

We report a case of a 5-year-old boy presenting to us with short stature. He was born of consanguineous parentage and was small for gestational age. He had severe short stature, with height Z score of -6.2 SD Score, markedly delayed skeletal age, low level of insulin-like growth factor 1, unstimulated growth hormone and hypoplastic anterior pituitary gland on MRI. He was advised growth hormone (GH) replacement at 2 years of age, but he did not receive it . Later on, he developed photosensitive telangiectatic lesions over face and required multiple hospital admissions for recurrent systemic infections. Genetic analysis confirmed the diagnosis of Bloom's syndrome. The present case report illustrates the need for high vigilance for conditions like Bloom's syndrome in growth hormone deficiency (GHD), in whom GH treatment could potentially be harmful. Bloom's syndrome with GHD is an exceedingly rare association., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Fanconi anaemia (FA), ataxia telangiectasia (A-T), Nijmegen breakage syndrome (NBS) and Bloom syndrome (BS) are clinically distinct, chromosome instability (or breakage) disorders. Each disorder has its own pattern of chromosomal damage, with cells from these patients being hypersensitive to particular genotoxic drugs, indicating that the underlying defect in each case is likely to be different. In addition, each syndrome shows a predisposition to cancer. Study of the molecular and genetic basis of these disorders has revealed mechanisms of recognition and repair of DNA double-strand breaks, DNA interstrand crosslinks and DNA damage during DNA replication. Specialist clinics for each disorder have provided the concentration of expertise needed to tackle their characteristic clinical problems and improve outcomes. Although some treatments of the consequences of a disorder may be possible, for example, haematopoietic stem cell transplantation in FA and NBS, future early intervention to prevent complications of disease will depend on a greater understanding of the roles of the affected DNA repair pathways in development. An important realization has been the predisposition to cancer in carriers of some of these gene mutations.

Bloom Syndrome (BSyn) is an autosomal recessive disorder that causes growth deficiency, endocrine abnormalities, photosensitive skin rash, immune abnormalities, and predisposition to early-onset cancer. The available treatments for BSyn are symptomatic, and early identification of complications has the potential to improve outcomes. To accomplish this, standardized recommendations for health supervision are needed for early diagnosis and treatment. The purpose of this report is to use information from the BSyn Registry, published literature, and expertise from clinicians and researchers with experience in BSyn to develop recommendations for diagnosis, screening, and treatment of the clinical manifestations in people with BSyn. These health supervision recommendations can be incorporated into the routine clinical care of people with BSyn and can be revised as more knowledge is gained regarding their clinical utility., (© 2018 Wiley Periodicals, Inc.)

Bloom syndrome (BS) is a rare, autosomal recessive genetic disorder characterized by short stature, a skin rash associated with sun exposure, and an elevated likelihood of developing cancers of essentially all types, beginning at an early age. Cancer is the leading cause of death for persons with BS, and its early onset results in a reported median lifespan of <30 years. With fewer than 300 documented cases since BS was first described in 1954, its rarity has challenged progress in advancing both the care of and the cure for persons with BS. Presently, there are no known clinically actionable targets specific to persons with this cancer predisposition syndrome, despite the fact that standard cancer treatments are often contraindicated or must be substantially modified for persons with BS. Herein, Zachary Rogers recounts his experience as a cancer patient with BS contemplating a substantially customized chemotherapy regimen that highlights the need for development of individualized treatments in the BS community. We also outline a patient-centered research and community action road map with the goal of improving and prolonging the lives of persons with Bloom syndrome, including the facilitation of precision medicine development specific to this condition., (© 2018 Campbell et al.; Published by Cold Spring Harbor Laboratory Press.)

Bloom's syndrome (BS) is an autosomal recessive disease, caused by mutations in the BLM gene. This gene codes for BLM protein, which is a helicase involved in DNA repair. DNA repair is especially important for the development and maturation of the T and B cells. Since BLM is involved in DNA repair, we aimed to study if BLM deficiency affects T and B cell development and especially somatic hypermutation (SHM) and class switch recombination (CSR) processes. Clinical data of six BS patients was collected, and immunoglobulin serum levels were measured at different time points. In addition, we performed immune phenotyping of the B and T cells and analyzed the SHM and CSR in detail by analyzing IGHA and IGHG transcripts using next-generation sequencing. The serum immunoglobulin levels were relatively low, and patients had an increased number of infections. The absolute number of T, B, and NK cells were low but still in the normal range. Remarkably, all BS patients studied had a high percentage (20-80%) of CD4+ and CD8+ effector memory T cells. The process of SHM seems normal; however, the Ig subclass distribution was not normal, since the BS patients had more IGHG1 and IGHG3 transcripts. In conclusion, BS patients have low number of lymphocytes, but the immunodeficiency seems relatively mild since they have no severe or opportunistic infections. Most changes in the B cell development were seen in the CSR process; however, further studies are necessary to elucidate the exact role of BLM in CSR.

DNA repair syndromes are heterogeneous disorders caused by pathogenic variants in genes encoding proteins key in DNA replication and/or the cellular response to DNA damage. The majority of these syndromes are inherited in an autosomal-recessive manner, but autosomal-dominant and X-linked recessive disorders also exist. The clinical features of patients with DNA repair syndromes are highly varied and dependent on the underlying genetic cause. Notably, all patients have elevated risks of syndrome-associated cancers, and many of these cancers present in childhood. Although it is clear that the risk of cancer is increased, there are limited data defining the true incidence of cancer and almost no evidence-based approaches to cancer surveillance in patients with DNA repair disorders. This article is the product of the October 2016 AACR Childhood Cancer Predisposition Workshop, which brought together experts from around the world to discuss and develop cancer surveillance guidelines for children with cancer-prone disorders. Herein, we focus on the more common of the rare DNA repair disorders: ataxia telangiectasia, Bloom syndrome, Fanconi anemia, dyskeratosis congenita, Nijmegen breakage syndrome, Rothmund-Thomson syndrome, and Xeroderma pigmentosum. Dedicated syndrome registries and a combination of basic science and clinical research have led to important insights into the underlying biology of these disorders. Given the rarity of these disorders, it is recommended that centralized centers of excellence be involved directly or through consultation in caring for patients with heritable DNA repair syndromes. Clin Cancer Res; 23(11); e23-e31. ©2017 AACR See all articles in the online-only CCR Pediatric Oncology Series., (©2017 American Association for Cancer Research.)

Genomic instability is a hallmark of cancer and aging. Premature aging (progeroid) syndromes are often caused by mutations in genes whose function is to ensure genomic integrity. The RecQ family of DNA helicases is highly conserved and plays crucial roles as genome caretakers. In humans, mutations in three RecQ genes - BLM, WRN, and RECQL4 - give rise to Bloom's syndrome (BS), Werner syndrome (WS), and Rothmund-Thomson syndrome (RTS), respectively. WS is a prototypic premature aging disorder; however, the clinical features present in BS and RTS do not indicate accelerated aging. The BLM helicase has pivotal functions at the crossroads of DNA replication, recombination, and repair. BS cells exhibit a characteristic form of genomic instability that includes excessive homologous recombination. The excessive homologous recombination drives the development in BS of the many types of cancers that affect persons in the normal population. Replication delay and slower cell turnover rates have been proposed to explain many features of BS, such as short stature. More recently, aberrant transcriptional regulation of growth and survival genes has been proposed as a hypothesis to explain features of BS., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Bloom syndrome is an extremely rare inherited disorder. We present a case of Bloom syndrome with a chromosomal study in a Mexican five-year-old patient who presented growth retardation, narrow facies with poikiloderma, café-au-lait, macules and photosensitivity.

In the early 1960s, J. German established the non-synchronous human DNA replication pattern in metaphases of cultured lymphocytes and fibroblasts. This could be used to distinguish several chromosomes of similar morphology. From 1965 on over the next 30 years, he and his coworkers systematically studied Bloom's syndrome in depth, cumulating in the identification in 1995 of the BLM gene as encoding a DNA helicase. © 2016 Wiley Periodicals, Inc., (© 2016 Wiley Periodicals, Inc.)

Bloom syndrome, a rare autosomal-recessive disorder, characteristically presents with photosensitivity, telangiectatic facial erythema, and growth deficiency. We present a case of Bloom syndrome with uncommon clinical manifestations including alopecia areata, eyebrow hair loss, flat nose, reticular pigmentation, and short sharpened distal phalanges with fingernails that were wider than they were long. We detected the Bloom syndrome gene, BLM, which is one of the members of the RecQ family of DNA helicases, and found changes in 2 heterozygous nucleotide sites in the patient as well as her father and mother.

The direct-to-consumer genetic testing debate reached a fever pitch in November 2013 when the US Food and Drug Administration (FDA) instructed 23andMe to discontinue marketing and sale of their Personal Genome Service. In 2015, 23andMe emerged with FDA approval to market a carrier test for Bloom syndrome only, and plans to release additional reports. The dust has settled and it is time to ask: What have we learned, and where do we go from here?, (© 2015 ASCPT.)

A 17-year-old Indian man was diagnosed with Bloom's syndrome at the age of 3 years. This is the first reported case of Bloom's in an Indian from the UK and the third case report from the British Isles. Bloom's is typically characterised by short stature, photosensitivity, telangiectatic erythema, learning difficulties, immunodeficiency and malignancy. He was born below the 0.4th centile and failed to gain weight as an infant. He presented in clinic with short stature, prominent facial features and hyperpigmented skin patches, which are all defining characteristics of Bloom's syndrome. Other case reports have documented early neoplasms, photosensitivity and learning difficulties in these patients; however, our patient is different, and currently attends a mainstream college, demonstrating little difficulty in coping with the work. To date, he has not presented with any malignancy or characteristic malar rash., (2016 BMJ Publishing Group Ltd.)

Bloom Syndrome (BS, MIM #210900) is an autosomal recessive genetic disorder caused by a mutation in the BLM gene, which codes for the DNA repair enzyme RecQL3 helicase. Without proper DNA repair mechanisms, abnormal DNA exchange takes place between sister chromatids and results in genetic instability that may lead to cancer, especially lymphoma and acute myelogenous leukemia, lower and upper gastrointestinal tract neoplasias, cutaneous tumors, and neoplasias in the genitalia and urinary tract. BS patients are usually of Ashkenazi Jewish descent and exhibit narrow facial features, elongated limbs, and several dermatologic complications including photosensitivity, poikiloderma, and telangiectatic erythema. The most concerning manifestation of BS is multiple malignancies, which require frequent screenings and strict vigilance by the physician. Therefore, distinguishing between BS and other dermatologic syndromes of similar presentation such as Rothmund-Thomson Syndrome, Erythropoietic Protoporphyria, and Cockayne Syndrome is paramount to disease management and to prolonging life. BS can be diagnosed through a variety of DNA sequencing methods, and genetic testing is available for high-risk populations. This review consolidates several sources on BS sequelae and aims to suggest the importance of differentiating BS from other dermatologic conditions. This paper also elucidates the recently discovered BRAFT and FANCM protein complexes that link BS and Fanconi anemia., (© 2014 The International Society of Dermatology.)

Background: GH treatment has become a frequently applied growth-promoting therapy in short children born small for gestational age (SGA). In some disorders GH treatment is contraindicated, eg, chromosomal breakage syndromes. Bloom syndrome is a rare chromosomal breakage syndrome characterized by severe pre- and postnatal growth deficiency, a photosensitive facial erythema, immunodeficiency, mental retardation or learning disabilities, endocrinopathies, and a predisposition to develop a wide variety of cancers., Objective: We report 2 patients with Bloom syndrome illustrating the variety in clinical manifestations. They were initially diagnosed with short stature after SGA birth and Silver Russell syndrome and treated with GH., Cases: Both patients presented with pre- and postnatal growth failure but no clear other characteristic features associated with Bloom syndrome. Photosensitive skin lesions developed only at a pubertal age and were minimal. Also, both children showed normal immunoglobulin levels, normal development, and no signs of endocrinopathies at start of GH. Dysmorphic features resembling Silver Russell syndrome were observed in both patients. Remarkably, during GH treatment IGF-1 levels increased to values greater than 3.5 SD score, with normal IGF binding protein-3 levels., Conclusion: Short children born SGA comprise a heterogeneous group. Bloom syndrome should be tested for in children with consanguineous parents, dysmorphic features (particularly resembling Silver Russell syndrome), skin abnormalities, and/or IGF-1 levels greater than 2.5 SD score during standard GH treatment with normal IGF binding protein-3 levels.

Bloom syndrome (congenital telangiectatic erythema) is a rare autosomal recessive disorder characterized by telangiectasias and photosensitivity, growth deficiency of prenatal onset, variable degrees of immunodeficiency, and increased susceptibility to neoplasms of many sites and types. We are reporting Bloom syndrome in two brothers from Kashmir (India), 8 and 6 years of age, who presented with erythematous rashes on the face, photosensitivity, and growth retardation.

Many recessive genetic disorders are found at a higher incidence in people of Ashkenazi Jewish (AJ) descent than in the general population. The American College of Medical Genetics and the American College of Obstetricians and Gynecologists have recommended that individuals of AJ descent undergo carrier screening for Tay Sachs disease, Canavan disease, familial dysautonomia, mucolipidosis IV, Niemann-Pick disease type A, Fanconi anemia type C, Bloom syndrome, and Gaucher disease. Although these recommendations have led to increased test volumes and number of laboratories offering AJ screening, well-characterized genomic reference materials are not publicly available. The Centers for Disease Control and Prevention-based Genetic Testing Reference Materials Coordination Program, in collaboration with members of the genetic testing community and Coriell Cell Repositories, have developed a panel of characterized genomic reference materials for AJ genetic testing. DNA from 31 cell lines, representing many of the common alleles for Tay Sachs disease, Canavan disease, familial dysautonomia, mucolipidosis IV, Niemann-Pick disease type A, Fanconi anemia type C, Bloom syndrome, Gaucher disease, and glycogen storage disease, was prepared by the Repository and tested in six clinical laboratories using three different PCR-based assay platforms. A total of 33 disease alleles was assayed and 25 different alleles were identified. These characterized materials are publicly available from Coriell and may be used for quality control, proficiency testing, test development, and research.

Syndromes involving premature skin aging provide outstanding models for a better understanding of both skin senescence and of the aging process in general. Although initially merely descriptive, these rare or indeed very rare conditions have been studied in detail and their genetic and biochemical background has been elucidated. The new data are now sufficiently accurate to allow the development of a new classification based on the underlying biochemical pathomechanisms. Three main subsets can be distinguished: progeroid syndromes with direct or indirect impairment of lamin A (progeria), syndromes involving dysfunction of the excision/repair apparatus (Cockayne syndrome), and conditions involving chromosome instability, particularly in the event of helicase mutation (Werner and Rothmund-Thomson syndromes, ataxia-telangiectasia). The diagnosis is still based on clinical examination in most cases, with the dermatologist commonly playing a key role because of the frequently obvious nature of skin changes, whereas other abnormalities may be less clear-cut or initially absent. Specialized genetic studies to confirm phenotypic hypothesis are increasingly available thanks to the development of reference centres. Although treatment continues to be symptomatic in most cases, recent advances in basic research have raised new hopes regarding targeted therapies, notably in progeria.

Bloom's syndrome (BS) is a rare autosomal recessive disease predisposing patients to all types of cancers affecting the general population. BS cells display a high level of genetic instability, including a 10-fold increase in the rate of sister chromatid exchanges, currently the only objective criterion for BS diagnosis. We have developed a method for screening the BLM gene for mutations based on direct genomic DNA sequencing. A questionnaire based on clinical information, cytogenetic features, and family history was addressed to physicians prescribing BS genetic screening, with the aim of confirming or guiding diagnosis. We report here four BLM gene mutations, three of which have not been described before. Three of the mutations are frameshift mutations, and the fourth is a nonsense mutation. All these mutations introduce a stop codon, and may therefore be considered to have deleterious biological effect. This approach should make it possible to identify new mutations and to correlate them with clinical information.

The RecQ helicases belong to the Superfamily II group of DNA helicases, and are defined by amino acid motifs that show sequence similarity to the catalytic domain of Escherichia coli RecQ. RecQ helicases have crucial roles in the maintenance of genome stability. In humans, there are five RecQ helicases and deficiencies in three of them cause genetic disorders characterised by cancer predisposition, premature aging and/or developmental abnormalities. RecQ helicase-deficient cells exhibit aberrant genetic recombination and/or DNA replication, which result in chromosomal instability and a decreased potential for proliferation. Here, we review the current knowledge of the molecular genetics of RecQ helicases, focusing on the human RecQ helicase disorders and mouse models of these conditions.

Purpose of Review: The delineation of syndromes carrying a predisposition to malignancy has led to great insights into the molecular biology of malignancy. Many such syndromes have cutaneous findings which can precede the development of neoplasia. Early recognition of the cutaneous stigmata of the genodermatoses with malignant potential can lead to early diagnosis and initiation of proper screening and treatment when indicated., Recent Findings: This article reviews 'classic' genodermatoses with malignant potential and highlights recent recommendations for screening and treatment. Additionally more recently delineated syndromes and their cutaneous findings are discussed., Summary: Certain inherited syndromes with a risk of neoplasia exhibit characteristic cutaneous findings. Recognition of these findings by the astute practitioner can lead to early intervention which can impact the course of these rare diseases.

In the literature, conflicting reports on the significance of false-positive maternal serum multiple marker testing for trisomy 18 are encountered; however, the biology of this finding is discussed infrequently. We present such a case in association with Bloom's syndrome in the fetus. The fetus had intrauterine growth restriction, seen early in the second trimester, oligohydramnios, and was delivered at 34 weeks of gestation for impending fetal compromise. We propose that the adverse outcome of the pregnancy with false-positive serum analyte testing for trisomy 18 might result from a small-sized placenta and perhaps pathology at receptor level., (Copyright (c) 2007 S. Karger AG, Basel.)

Bloom syndrome (BS) is a rare autosomal recessive genetic disorder characterized by lupus-like erythematous facial telangiectasia, sun sensitivity, infertility, stunted growth and a high predisposition to various types of cancer. Chromosomal abnormalities are hallmarks of this disorder, and high frequencies of sister chromatid exchanges and quadriradial configurations in lymphocytes and fibroblasts are diagnostic features. BLM is the causative gene for BS. We investigated the mutation in the BLM gene in 4 Japanese BS kindreds. Taken together with previously documented mutations, 2 kindreds were homozygous for 631delCAA and 2 were compound heterozygous for 631delCAA. The silent mutation of A1055C (Thr to Thr) was detected in control Japanese individuals. The 6-bp deletion/7-bp insertion at position 2,281, which most Askenazi Jewish BS patients carry, was not detected in 200 Japanese alleles. These results suggest that 631delCAA is a relatively common mutation among the Japanese BS patients.

Bloom syndrome is a rare autosomal recessive genetic disorder characterized by growth deficiency, unusual facies, sun-sensitive telangiectatic erythema, immunodeficiency and predisposition to cancer. The causative gene for Bloom syndrome is BLM, which encodes the BLM RecQ helicase homolog protein. The first part of this review describes a long-term follow-up study of two Bloom syndrome siblings. Subsequently, the focus is placed on the functional domains of BLM. Laboratory diagnosis of Bloom syndrome by detecting mutations in BLM is laborious and impractical, unless there are common mutations in a population. Immunoblot and immunohistochemical analyses for the detection of the BLM protein using a polyclonal BLM antibody, which are useful approaches for clinical diagnosis of Bloom syndrome, are also described. In addition, a useful adjunct for the diagnosis of Bloom syndrome in terms of the BLM function is investigated, since disease cells must have the defective BLM helicase function. This review also discusses the nuclear localization signal of BLM, the proteins that interact with BLM and tumors originating from Bloom syndrome.

Ophthalmic examination of a girl admitted with the complaint of growth failure revealed retinal hard drusen. It was surprising to observe drusen in a child because they represent an age-related degenerative change in normal individuals. After further evaluation, she was diagnosed to have Bloom syndrome, a premature aging syndrome. To the authors' knowledge, this is the first case of Bloom syndrome associated with drusen. It is probable that not only aging but also other fundamental cell processes, especially uncontrolled cell proliferation, might be similarly affected and might follow a more rapid course in this inherited condition presenting with drusen. The authors suggest paying extra attention to drusen during the ophthalmic assessment in the diagnosis of all Bloom syndrome patients; it may be prudent to watch more carefully for the development of cancer in patients with drusen than those without drusen.

The aim of carrier testing is to identify carrier couples at risk of having offspring with a serious genetic (autosomal recessive) disorder. Carrier couples are offered genetic consultation where their reproductive options, including prenatal diagnosis, are explained. The Ashkenazi Jewish population is at increased risk for several recessively inherited disorders (Tay-Sachs disease, Cystic fibrosis, Canavan disease, Gaucher disease, Familial Dysautonomia, Niemann-Pick disease, Fanconi anemia, and Bloom syndrome). Unlike Tay-Sachs disease, there is no simple biochemical or enzymatic test to detect carriers for these other disorders. However, with the rapid identification of disease-causing genes in recent years, DNA-based assays are increasingly available for carrier detection. Approximately 5% of the world's population carries a mutation affecting the globin chains of the hemoglobin molecule. Among the most common of these disorders are the thalassemias. The global birth rate of affected infants is at least 2 per 1000 (in unscreened populations), with the greatest incidence in Southeast Asian, Indian, Mediterranean, and Middle Eastern ethnic groups. Carriers are detected by evaluation of red cell indices and morphology, followed by more sophisticated hematological testing and molecular analyses. The following issues need to be considered in the development of a carrier screening program: (1) test selection based on disease severity and test accuracy; (2) funding for testing and genetic counselling; (3) definition of the target population to be screened; (4) development of a public and professional education program; (5) informed consent for screening; and (6) awareness of community needs.

Bloom syndrome (BS) is a rare autosomal recessive genetic disorder characterized by growth deficiency, unusual facies, sun-sensitive telangiectatic erythema, immunodeficiency and predisposition to cancer. The causative gene for BS is the BLM gene which encodes the BLM RecQ helicase protein. The BLM gene has 4437 bp and encodes 1417 amino acids. The detection of BLM gene mutations for laboratory diagnosis of BS is laborious and impractical, unless there are common mutations in a population. Here we describe the immunoblot and immunohistochemical analyses for the detection of the BLM protein using a polyclonal BLM antibody. The BLM gene and protein were consistently and clearly detected in Epstein-Barr virus (EBV)-transformed or phytohemagglutinin (PHA)-stimulated lymphoblasts from control and various human hematopoietic cell lines. In a 7-week old human fetal brain, the BLM gene expression was strongly detected in contrast to an adult human brain. The BLM protein was not detected in EBV-transformed lymphoblasts from three BS patients. By immunohistochemistry, nuclear dots of the BLM protein were detected in both EBV-transformed lymphoblasts and PHA-stimulated lymphoblasts from the control. However, in lymphoblasts from BS patients no nuclear dots of the BLM protein were detected. These results indicate that the combinational analysis of immunoblotting and immunohistochemistry is a useful approach to screening of BS, although a mutation analysis is necessary for a definitive diagnosis of BS.

The chromosome instability syndromes, ataxia telangiectasia (A-T), Fanconi anaemia (FA) and Bloom syndrome (BS) have been known for many years. More recently Nijmegen breakage syndrome (NBS) and ataxia telangiectasia-like disorder (ATLD) have been identified. A-T, ATLD and NBS form a group of disorders all of which show very similar cellular features that result from the consequences of increased sensitivity to ionizing radiation (IR). They also share some clinical features, particularly A-T and ATLD, and all show an immunodeficiency. A-T and NBS both show a predisposition to lymphoid tumours. Fanconi anaemia can be caused by mutations in eight different genes, although the majority of mutations are accounted for by FANCA and FANCC. The very rare Bloom syndrome is caused by mutation in a single gene, BLM. An important feature which all of these disorders have in common is that the genes identified are involved in aspects of recombination repair of DNA damage., (Copyright 2001 Harcourt Publishers Ltd.)

Two requirements for the cytogenetic analysis of sister-chromatid exchanges (SCEs) in somatic cells are (1) a population of actively proliferating cells that will provide an adequate number of metaphases and (2) sister chromatids that in some way are differentially labeled or stained in the metaphases. SCEs can be recognized as abrupt discontinuities in the staining patterns of the two chromatids of a metaphase chromosome at what appear to be identical sites, with reciprocal switching from one chromatid to its sister. This protocol uses phytohemagglutinin (PHA)-stimulated cultures of blood lymphocytes as a source of proliferating cells. The cells are incubated with the thymidine analog BrdU. Slides prepared from fixed cells with BrdU-substituted chromosomes are treated with Hoechst 33258, exposed to light and heat, and then Giemsa-stained to produce differentially stained chromosomes. The chromatids with bifilar substitution exhibit a lighter purple stain than their unifilarly substituted sister chromatids.

Chromosome instability is a characteristic cytogenetic feature of a number of genetically determined disorders collectively called as the chromosome breakage syndromes or DNA-repair disorders. They are characterized by susceptibility to chromosomal breakages, increased frequency of breaks and interchanges occurring either spontaneously or following exposure to various DNA-damaging agents. These diseases are a group of genetic disorders sharing a number of features. They are all autosomal recessive, show an increased tendency for chromosomal aberrations and to develop malignancies. The principal diseases in this group having a diverse etiology and clinical manifestations include Fanconi anemia (FA), ataxia telangiectasia (AT), Nijmegen breakage syndrome (NBS), Bloom syndrome (BS), xeroderma pigementosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD). The underlying defect in these syndromes is the inability to repair a particular type of DNA damage. A number of repair disorder phenotypes are caused by more than one gene. The diagnosis of these syndromes is made by the characteristic clinical features specific to each disease, but the definitive diagnosis is achieved by laboratory investigations such as cytogenetic, biochemical and molecular methods. The importance of prenatal diagnosis and our experience are discussed in this article.

Bloom syndrome is a rare genodermatosis characterized by photosensitivity, telangiectasias, growth retardation and malignancies. Eye findings have rarely been mentioned in case reports of this syndrome. We report a child with Bloom syndrome who had pronounced bulbar conjunctival telangiectasia originally diagnosed as episcleritis. Bulbar telangiectasia are frequently described in other genodermatoses such as ataxia telangiectasia and hereditary hemorrhagic telangiectasia, but are infrequently noted in Bloom syndrome. Previously described eye findings in Bloom syndrome are reviewed and the differential diagnosis of bulbar telangiectasia is discussed.

As of 1996 the 100th cancer was diagnosed in Bloom's syndrome. The cancers have been regularly documented since 1960 in a program of surveillance referred to as the Bloom's Syndrome Registry. Tabulated here are their types and ages of onset. The 100 cancers arose in 71 of the 168 registered individuals. Represented in Bloom's syndrome are both the cancers that commonly affect the general population and the rare tumors of early childhood. This body of information has become sufficiently large to be useful to geneticists and physicians in advising affected families concerning cancer risk. Of more general significance, however, the distribution of cancer sites and types sets Bloom's syndrome apart from other cancer-predisposing genetically determined conditions, affirming its experimental value as a model for analyzing the nonenvironmental component in the etiology of the generality of human cancer.

Two children presenting with sporadic unilateral retinoblastoma and exhibiting a high degree of chromosome breakage were noted to have unusual facies, microcephaly and abnormal skin pigmentation. In the first child the pattern of both spontaneous and mitomycin-C-induced chromosome breakage was characteristic of Fanconi's anaemia although the degree of breakage was extreme. She also exhibited a striking increase in X-ray-induced chromosomal damage in G0 lymphocytes as measured by dicentric formation and increase in chromatid-type aberrations. She had a number of typical clinical features, including cafe-au-lait patches and abnormalities involving the kidney; however, she demonstrated neither the hypoplasia of radius and thumb nor the typical aplastic phase of this disorder. At age 22 months the child became anaemic with trilineage myelodysplasia, which was rapidly followed by the development of acute myeloblastic leukaemia. The early onset (at age 4 months) of retinoblastoma may have been associated with the underlying genomic instability. The second child exhibited a pattern of chromosome breakage characteristic of Bloom's syndrome, in addition to a moderate increase in damage induced by mytomycin-C. She had the typical stunted growth and malar hypoplasia of Bloom's syndrome although she did not demonstrate the frequently described erythematous 'butterfly rash' Although patients with Fanconi's anaemia and Bloom's syndrome are recognised to be at an increased risk of cancer, retinoblastoma has not previously been described in patients with either condition. We suggest that underlying recessive chromosome breakage syndromes may be underdiagnosed in paediatric cancer patients, with important implications for prognosis and genetic counselling.

Cultures of a chorion biopsy taken from a pregnancy at risk of Bloom's syndrome revealed the high sister chromatid exchange frequency diagnostic of this rare disorder. To obtain the result, cultures were grown under standard conditions, with the addition of 10 microM 5'-bromodeoxyuridine for the final 48 h of incubation. This result demonstrates the feasibility of early prenatal diagnosis of Bloom's syndrome.

Bloom syndrome (BS) is an autosomal recessive disorder characterized by increases in the frequency of sister-chromatid exchange and in the incidence of malignancy. Chromosome-transfer studies have shown the BS locus to map to chromosome 15q. This report describes a subject with features of both BS and Prader-Willi syndrome (PWS). Molecular analysis showed maternal uniparental disomy for chromosome 15. Meiotic recombination between the two disomic chromosomes 15 has resulted in heterodisomy for proximal 15q and isodisomy for distal 15q. In this individual BS is probably due to homozygosity for a gene that is telomeric to D15S95 (15q25), rather than to genetic imprinting, the mechanism responsible for the development of PWS. This report represents the first application of disomy analysis to the regional localization of a disease gene. This strategy promises to be useful in the genetic mapping of other uncommon autosomal recessive conditions.

A wide variety of unusual genodermatoses may be encountered by physicians during training or later in their practice. We have briefly described some of these and have outlined laboratory studies that may aid in their diagnosis.