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Trichoscopy allows analyzing the structure and size of growing hair shafts in their natural environment in children and adults. The method replaces light microscopy, which requires pulling of multiple hairs for investigation. In monilethrix, trichoscopy shows uniform elliptical nodosities with intermittent constrictions. In trichorrhexis nodosa nodular thickenings along hairs shafts are visible (low magnification) or splitting into numerous small fibers along the hair shaft may be observed (high magnification). In trichorrhexis invaginata (bamboo hair) the hair shaft telescopes into itself at several points along the shaft. Trichoscopy shows small nodules along the shaft. Hairs bend and break in these diseases. Trichoscopy of pili torti shows twists of hair shafts along their long axis. In pili annulati hair shafts with alternating white and dark bands are visible. In woolly hair the examination demonstrates hair shafts with waves at very short intervals. For trichothiodystrophy polarized trichoscopy should be used. In ectodermal dysplasias, trichoscopy shows a variety of hair abnormalities, but the most characteristic finding is hair shaft pigmentation heterogeneity.

Trichothiodystrophy type 4 is a rare autosomal recessive and ectodermal disorder, characterized by dry, brittle, sparse and sulfur-deficient hair and other features like intellectual disability, ichthyotic skin and short stature, caused by a homozygous mutation in MPLKIP gene. Glutaric aciduria type 3 is caused by a homozygous mutation in SUGCT gene with no distinctive phenotype. Both genes are localized on chromosome 7 (7p14). We report an 8-year-old female with short stature, microcephaly, development delay, intellectual disability and hair characterized for dark, short, coarse, sparse and brittle associated to classical trichorrhexis microscopy pattern. Chromosome microarray analysis showed a 125 kb homozygous pathogenic deletion, which includes genes MPLKIP and SUGCT, not described before. This is the first case described in Peru of a novel contiguous gene deletion of Trichothiodystrophy type 4 and Glutaric aciduria type 3 performed by chromosome microarray analysis, highlighting the contribution and importance of molecular technologies on diagnosis of rare genetic conditions.

Xeroderma pigmentosum (XP), trichothiodystrophy (TTD) and Cockayne syndrome (CS) are rare genetic diseases characterized by a large range of clinical symptoms. However, they are all associated with defects in nucleotide excision repair (NER), the system responsible for removing bulky DNA lesions such as those generated by UV light: cyclobutane pyrimidine dimers (CPDs) and pyrimidine-pyrimidone photoproducts (6-4 PPs). Over the past years, detailed structural and biochemical information on NER-associated proteins has emerged. In the first part of the article we briefly present the main steps of the NER pathway with an emphasis on the precise role of certain proteins. Further, we focus on clinical manifestations of the disorders and describe the diagnostic procedures. Then we consider how current therapy and advanced technology could improve patients' quality of life. Although to date the discussed diseases remain incurable, effective sun protection, a well thought out diet, and holistic medical care provide longer life and better health. This review summarizes the current state of knowledge regarding the epidemiology of NER-associated diseases, their genetic background, clinical features, and treatment options.

The general transcription factor IIE (TFIIE) is essential for transcription initiation by RNA polymerase II (RNA pol II) via direct interaction with the basal transcription/DNA repair factor IIH (TFIIH). TFIIH harbors mutations in two rare genetic disorders, the cancer-prone xeroderma pigmentosum (XP) and the cancer-free, multisystem developmental disorder trichothiodystrophy (TTD). The phenotypic complexity resulting from mutations affecting TFIIH has been attributed to the nucleotide excision repair (NER) defect as well as to impaired transcription. Here, we report two unrelated children showing clinical features typical of TTD who harbor different homozygous missense mutations in GTF2E2 (c.448G>C [p.Ala150Pro] and c.559G>T [p.Asp187Tyr]) encoding the beta subunit of transcription factor IIE (TFIIEβ). Repair of ultraviolet-induced DNA damage was normal in the GTF2E2 mutated cells, indicating that TFIIE was not involved in NER. We found decreased protein levels of the two TFIIE subunits (TFIIEα and TFIIEβ) as well as decreased phosphorylation of TFIIEα in cells from both children. Interestingly, decreased phosphorylation of TFIIEα was also seen in TTD cells with mutations in ERCC2, which encodes the XPD subunit of TFIIH, but not in XP cells with ERCC2 mutations. Our findings support the theory that TTD is caused by transcriptional impairments that are distinct from the NER disorder XP.

Trichothiodystrophy (TTD), also known as sulfur-deficient brittle hair syndrome, is a rare autosomal recessive multisystem disorder, which manifests with brittle hair, mental retardation, ichthyosis and decreased fertility. Mutations in the TTDN1 (C7orf11) gene have been shown to cause a nonphotosensitive type of trichothiodystrophy. We report of a 19 years old male, born to consanguineous parents of Arab-Muslim descent, who presented due to severe renal failure, but exhibited additional unique features, including developmental delay, mental retardation, splenomegaly, pancytopenia, hypogonadism and brittle hair. Following the clinical diagnosis of nonphotosensitive TTD, sequencing of the coding exons of C7orf11 was performed and revealed the patient to be homozygous for a novel c.505dupA mutation. As the severe renal failure following which the proband was referred to our care is not typically characteristic of this disorder, its significance is discussed. Molecular diagnosis of this highly affected family should enable genetic counseling and prenatal diagnosis for future pregnancies.

Nucleotide excision repair (NER) is an important DNA repair pathway involved in the removal of a wide array of DNA lesions. The absence or dysfunction of NER results in the following distinct disorders: xeroderma pigmentosum (XP), Cockayne syndrome (CS), cerebro-oculo-facio-skeletal (COFS) syndrome, UV-sensitive syndrome (UVSS), trichothiodystrophy (TTD), or combined syndromes including XP/CS, XP/TTD, CS/TTD, and COFS/TTD. In addition to their well-characterized role in the NER signaling pathway, NER factors also seem to be important in biological processes that are not directly associated with DNA damage responses, including mitochondrial function and redox homeostasis. The potential causative role of these factors in the large clinical spectrum seen in NER diseases is discussed in this review.

The ichthyoses encompass a variety of genetic disorders marked by abnormal epidermal differentiation. The neonatal period is critical for patients with ichthyosis because of the risk for significant associated morbidity and mortality, with the majority of complications arising as a result of impaired barrier function. This article reviews presentations of ichthyosis in the neonate, outlines risks and complications, and provides strategies for management.

MRI: magnetic resonance imaging NIH: National Institutes of Health TTD: trichothiodystrophy XP: xeroderma pigmentosum CASE SUMMARY History A 4-year-old Caucasian girl presented to the National Institutes of Health (NIH) for evaluation of sparse brittle hair, developmental delay, poor growth, recurrent infections, and photosensitivity (Fig 1 and Table I). The patient was born preterm at 35 weeks after a pregnancy complicated by elevated maternal alpha-fetoprotein at 16 weeks and pregnancy-induced hypertension beginning at 26 weeks. At birth, her skin showed generalized erythroderma and she was described as having a collodion membrane (Fig 1, A) that resolved over 2.5 weeks. By 1 month of age, the patient was reported to have congenital ichthyosis and mild scaling on her scalp, trunk, and lower extremities. By 23 months, she was reported to sunburn with minimal sun exposure and sweat very little in hot environments. Short brittle hair, nail spooning, head tremor (titubation), and asymmetric horizontal nystagmus were also noted. The patient did not sit unassisted until 12 months and did not crawl until 22 months.

To get a clue to understand how mutations in the XPD gene result in different skin cancer susceptibilities in patients with xeroderma pigmentosum (XP) or trichothiodystrophy (TTD), a thorough understanding of their nucleotide excision repair (NER) defects is essential. Here, we extensively characterize the possible causes of NER defects in XP-D and in TTD fibroblasts. The 3 XP-D cell strains examined were similarly deficient in repairing UV-induced cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts (6-4PPs) from genomic DNA. The severity of NER defects correlated with their UV sensitivities. Possible alterations of TFIIH (which consists of 10 subunits including XPD) were then examined. All XP-D cell strains were normal in their concentrations of TFIIH, and displayed normal abilities to recruit TFIIH to sites of UV-induced DNA damage. However, replication protein A (RPA; single-stranded DNA binding protein) accumulation at DNA damage sites, which probably reflects the in vivo XPD helicase activity of TFIIH, is similarly impaired in all XP-D cell strains. Meanwhile, all 3 TTD cell strains had approximately 50% decreases in cellular TFIIH content. Importantly, 2 of the 3 TTD cell strains, which carry the major XPD mutations found in TTD patients, showed defective recruitment of TFIIH to DNA damage sites. Moreover, RPA accumulation at damage sites was impaired in all TTD cell strains to different degrees, which correlated with the severity of their NER defects. These results demonstrate that XP-D and TTD cells are both deficient in the repair of CPDs and 6-4PPs, but TTD cells have more multiple causes for their NER defects than do XP-D cells. Since TFIIH is a repair/transcription factor, TTD-specific alterations of TFIIH possibly result in transcriptional defects, which might be implication for the lack of increased incidence of skin cancers in TTD patients.

Nucleotide excision repair (NER) is a multi-step DNA repair mechanism that removes helix-distorting modified nucleotides from the genome. NER is divided into two subpathways depending on the location of DNA damage in the genome and how it is first detected. Global genome NER identifies and repairs DNA lesions throughout the genome. This subpathway of NER primarily protects against the accumulation of mutations in the genome. Transcription-coupled (TC) NER rapidly repairs lesions in the transcribed strand of DNA that block transcription by RNA polymerase II. TC-NER prevents cell death in response to stalled transcription. Defects in NER cause three distinct human diseases: xeroderma pigmentosum, Cockayne syndrome and trichothiodystrophy. Each of these syndromes is characterized by premature onset of pathologies that overlap with those associated with old age in humans. This reveals the contribution of DNA damage to multiple age-related diseases. Tissues affected include the skin, eye, bone marrow, nervous system and endocrine axis. This review emphasizes accelerated aging associated with xeroderma pigmentosum and discusses the cause of these pathologies, either mutation accumulation or cell death as a consequence of failure to repair DNA damage.

SummaryThe XPD helicase (Rad3 in Saccharomyces cerevisiae) is a component of transcription factor IIH (TFIIH), which functions in transcription initiation and Nucleotide Excision Repair in eukaryotes, catalyzing DNA duplex opening localized to the transcription start site or site of DNA damage, respectively. XPD has a 5′ to 3′ polarity and the helicase activity is dependent on an iron-sulfur cluster binding domain, a feature that is conserved in related helicases such as FancJ. The xpd gene is the target of mutation in patients with xeroderma pigmentosum, trichothiodystrophy, and Cockayne's syndrome, characterized by a wide spectrum of symptoms ranging from cancer susceptibility to neurological and developmental defects. The 2.25 Å crystal structure of XPD from the crenarchaeon Sulfolobus tokodaii, presented here together with detailed biochemical analyses, allows a molecular understanding of the structural basis for helicase activity and explains the phenotypes of xpd mutations in humans.