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Background and Clinical Significance: Mucopolysaccharidosis type VII (MPS VII), an ultrarare lysosomal storage disorder caused by β-glucuronidase deficiency, presents significant therapeutic challenges. Given its extreme rarity and limited treatment experience in Asian populations, documenting long-term treatment outcomes is crucial for advancing clinical knowledge and improving patient care. Case Presentation: We report a 3-year follow-up of enzyme replacement therapy (ERT) in the first Taiwanese case of MPS VII. The patient, who initially presented with hydrops fetalis and developmental delay, was diagnosed at age 4 through genetic analysis, which revealed compound heterozygous variants of c.104C > A (p.Ser35Ter) and c.1454C > T (p.Ser485Phe) on the GUSB gene. ERT with vestronidase alfa was initiated at age 6. During the follow-up period, significant clinical improvements were observed, including elimination of oxygen dependency, with BiPAP needed only during sleep; changes in mobility, with 6-min walk test distance showing an initial decline from 130 to 70 m followed by partial recovery to 95 m after multiple orthopedic surgeries; and steady progression of growth parameters showed, with height increasing from 110 to 118 cm. Urinary glycosaminoglycan (GAG) levels measured by dimethylmethylene blue spectrophotometry decreased and stabilized. The patient's cardiac and hepatic conditions remained stable, although splenomegaly persisted. No severe adverse events were reported during ERT. Conclusions: This case demonstrates the effectiveness and safety of long-term ERT in MPS VII, particularly in improving respiratory function and physical performance. Our experience highlights the importance of early diagnosis and treatment initiation, while providing valuable insights into the management of this ultrarare disease in the Asian population. [ABSTRACT FROM AUTHOR]

Background: Lesch–Nyhan syndrome (LNS) is a rare X-linked recessive metabolic disorder caused by mutations in the HPRT1 gene, resulting in hypoxanthine–guanine phosphoribosyltransferase (HPRT) deficiency. Early diagnosis is critical for optimizing management and improving outcomes. This study presents a case series of three Taiwanese patients diagnosed at a single medical center. Methods: Exome sequencing and biochemical testing were used to confirm the diagnoses. Early clinical manifestations, including hyperuricemia, hypotonia, and developmental delay, were documented during the initial stages of the disease. Results: All three patients had hyperuricemia, hypotonia, spasticity, and motor developmental delay. Pathogenic variants in the HPRT1 gene were identified in two patients, while the third was confirmed by biochemical testing. Two patients had orange-colored crystalline deposits in their diapers, indicative of hyperuricosuria. Self-injurious behavior had not yet developed in two patients due to their young age. Conclusions: Early clinical features such as hyperuricemia, hypotonia, and motor delay may suggest LNS in infancy. Molecular genetic testing, particularly whole exome sequencing, can facilitate an early diagnosis before specific manifestations occur, enabling timely interventions and improving patient outcomes. [ABSTRACT FROM AUTHOR]

Kabuki syndrome (KS) is a rare genetic disorder characterized by distinct facial features, intellectual disability, and multiple congenital anomalies. We conducted a comprehensive analysis of the genetic and phenotypic spectrum of KS in a Taiwanese patient group of 23 patients. KMT2D variants were found in 22 individuals, with missense (26.1%), nonsense (21.7%), and frameshift (17.4%) variants being the most prevalent. One patient had a KMT2D variant of uncertain significance. The most common clinical characteristics included distinct facial features (100%), intellectual disability (100%), developmental delay (95.7%), speech delay (78.3%), hypotonia (69.6%), congenital heart abnormalities (69.6%), and recurrent infections (65.2%). Other abnormalities included hearing loss (39.1%), seizures (26.1%), cleft palate (26.1%), and renal anomalies (21.7%). This study broadens the mutational and phenotypic spectrum of KS in the Taiwanese population, highlighting the importance of comprehensive genetic testing and multidisciplinary clinical evaluations for diagnosis and treatment. [ABSTRACT FROM AUTHOR]

Background: We clinically and genetically evaluated a Taiwanese boy presenting with developmental delay, organomegaly, hypogammaglobulinemia and hypopigmentation without osteopetrosis. Whole‐exome sequencing revealed a de novo gain‐of‐function variant, p.Tyr715Cys, in the C‐terminal domain of ClC‐7 encoded by CLCN7. Methods: Nicoli et al. (2019) assessed the functional impact of p.Tyr715Cys by heterologous expression in Xenopus oocytes and evaluating resulting currents. Results: The variant led to increased outward currents, indicating it underlies the patient's phenotype of lysosomal hyperacidity, storage defects and vacuolization. This demonstrates the crucial physiological role of ClC‐7 antiporter activity in maintaining appropriate lysosomal pH. Conclusion: Elucidating mechanisms by which CLCN7 variants lead to lysosomal dysfunction will advance understanding of genotype–phenotype correlations. Identifying modifier genes and compensatory pathways may reveal therapeutic targets. Ongoing functional characterization of variants along with longitudinal clinical evaluations will continue advancing knowledge of ClC‐7's critical roles and disease mechanisms resulting from its dysfunction. Expanded cohort studies are warranted to delineate the full spectrum of associated phenotypes. [ABSTRACT FROM AUTHOR]

Congenital heart defects (CHDs) affect a substantial proportion of patients with Kabuki syndrome. However, the prevalence and type of CHD and the genotype–phenotype correlations in Asian populations are not fully elucidated. This study performed a retrospective analysis of 23 Taiwanese patients with molecularly confirmed Kabuki syndrome. Twenty-two patients presented with pathogenic variants in the KMT2D gene. Comprehensive clinical assessments were performed. A literature review was conducted to summarize the spectrum of CHDs in patients with Kabuki syndrome. In total, 16 (73.9%) of 22 patients with pathogenic KMT2D variants had CHDs. The most common types of CHD were atrial septal defects (37.5%), ventricular septal defects (18.8%), coarctation of the aorta (18.8%), bicuspid aortic valve (12.5%), persistent left superior vena cava (12.5%), mitral valve prolapse (12.5%), mitral regurgitation (12.5%), and patent ductus arteriosus (12.5%). Other cardiac abnormalities were less common. Further, there were no clear genotype–phenotype correlations found. A literature review revealed similar patterns of CHDs, with a predominance of left-sided obstructive lesions and septal defects. In conclusion, the most common types of CHDs in Taiwanese patients with Kabuki syndrome who presented with KMT2D mutations are left-sided obstructive lesions and septal defects. [ABSTRACT FROM AUTHOR]