Fabry disease in infancy and early childhood: a systematic literature review.

PURPOSE: Fabry disease is a pan-ethnic, progressive, X-linked genetic disorder that commonly presents in childhood and is caused by deficient activity of the lysosomal enzyme alpha-galactosidaseA (α-gal A). Symptoms of Fabry disease in the pediatric population are well described for patients over five years of age; however, data are limited for infancy and early childhood. The purpose of this article is to delineate the age of detection for specific Fabry symptoms in early childhood. METHODS: A systematic retrospective analysis of PubMed indexed, peer-reviewed publications and case reports in the pediatric Fabry population was performed to review symptoms in patients reported before 5 years of age. RESULTS: The most frequently reported symptom in all age groups under 5 years was acroparesthesias/neuropathic pain, reported in 9 children, ranging in age from 2.0-4.0 years. Also notable is the frequency of gastrointestinal issues reported in 6 children aged 1.0-4.1 years of age. CONCLUSION: This article finds clear evidence that symptoms can occur in early childhood, before age 5 years. Given early presenting symptoms and the ability to monitor these disease hallmarks, a timely referral to a medical geneticist or other specialty clinician experienced in managing children with Fabry disease is strongly indicated.

Diagnosis of mitochondrial disorders by concomitant next-generation sequencing of the exome and mitochondrial genome.

Mitochondrial diseases are notoriously difficult to diagnose due to extreme locus and allelic heterogeneity, with both nuclear and mitochondrial genomes potentially liable. Using exome sequencing we demonstrate the ability to rapidly and cost effectively evaluate both the nuclear and mitochondrial genomes to obtain a molecular diagnosis for four patients with three distinct mitochondrial disorders. One patient was found to have Leigh syndrome due to a mutation in MT-ATP6, two affected siblings were discovered to be compound heterozygous for mutations in the NDUFV1 gene, which causes mitochondrial complex I deficiency, and one patient was found to have coenzyme Q10 deficiency due to compound heterozygous mutations in COQ2. In all cases conventional diagnostic testing failed to identify a molecular diagnosis. We suggest that additional studies should be conducted to evaluate exome sequencing as a primary diagnostic test for mitochondrial diseases, including those due to mtDNA mutations.

Fertility Management in Cystinosis: A Clinical Perspective.

Cystinosis is a rare, inherited, lysosomal storage disorder characterized by the progressive accumulation of intralysosomal cystine and subsequent organ and tissue damage. The kidneys are the first and most severely impacted organ. Although cystinosis was once considered a fatal pediatric disease, patients with cystinosis are living well into adulthood with advances in medical care, including kidney transplant and early and continuous use of cysteamine therapy. This increase in life expectancy has revealed an extrarenal phenotype of cystinosis that emerges in adolescence and adulthood, affecting nearly all body systems, including the endocrine and reproductive systems. As individuals with cystinosis are planning for the future, reproductive health and fertility have become areas of increased focus. This narrative review aims to summarize the current understanding of reproductive health and fertility in patients with cystinosis and discuss practical considerations for monitoring and managing these complications.

3-Hydroxyisobutyrate aciduria and mutations in the ALDH6A1 gene coding for methylmalonate semialdehyde dehydrogenase.

3-hydroxyisobutyric aciduria is an organic aciduria with a poorly understood biochemical basis. It has previously been assumed that deficiency of 3-hydroxyisobutyrate dehydrogenase (HIBADH) in the valine catabolic pathway is the underlying enzyme defect, but more recent evidence makes it likely that individuals with 3-hydroxyisobutyryic aciduria represent a heterogeneous group with different underlying mechanisms, including respiratory chain defects or deficiency of methylmalonate semialdehyde dehydrogenase. However, to date methylmalonate semialdehyde dehydrogenase deficiency has only been demonstrated at the gene level for a single individual. We present two unrelated patients who presented with developmental delay and increased urinary concentrations of 3-hydroxyisobutyric acid. Both children were products of consanguineous unions and were of European or Pakistani descent. One patient developed a febrile illness and subsequently died from a hepatoencephalopathy at 2 years of age. Further studies were initiated and included tests of the HIBADH enzyme in fibroblast homogenates, which yielded normal activities. Sequencing of the ALDH6A1 gene (encoding methylmalonate semialdehyde dehydrogenase) suggested homozygosity for the missense mutation c.785 C > A (S262Y) in exon 7 which was not found in 210 control alleles. Mutation analysis of the ALDH6A1 gene of the second patient confirmed the presence of a different missense mutation, c.184 C > T (P62S), which was also identified in 1/530 control chromosomes. Both mutations affect highly evolutionarily conserved amino acids of the methylmalonate semialdehyde dehydrogenase protein. Mutation analysis in the ALDH6A1 gene can reveal a cause of 3-hydroxyisobutyric aciduria, which may present with only slightly increased urinary levels of 3-hydroxyisobutyric acid, if a patient is metabolically stable.

The Role of Genetic Counseling in Pompe Disease After Patients Are Identified Through Newborn Screening.

An important part of the coordinated care by experienced health care teams for all Pompe disease patients, whether diagnosed through newborn screening (NBS), clinical diagnosis, or prenatal diagnosis, is genetic counseling. Genetic counseling helps families better understand medical recommendations and options presented by the patient's health care team so they can make informed decisions. In addition to providing important information about the inheritance and genetic risks, genetic counseling also provides information about Pompe disease and available treatments and resources and should be offered to families with an affected child and all adults diagnosed with Pompe disease. Although the need for genetic counseling after a positive newborn screen for Pompe disease is recognized, the role that genetic counseling plays for both families of affected patients and health care teams is not fully understood. Consistent best genetic counseling practices also are lacking. The guidance in this article in the "Newborn Screening, Diagnosis, and Treatment for Pompe Disease" supplement is derived from expert consensus from the Pompe Disease Newborn Screening Working Group. It is intended to help guide genetic counseling efforts and provide a clear understanding of the role for families or carriers of Pompe disease identified through NBS; explain special considerations (eg, diagnosis of late-onset Pompe disease before the appearance of symptoms) and the impact and implications associated with a diagnosis (eg, determination of genetic risk and carrier status and preconception counseling); and provide health care teams caring for patients with a framework for a standardized approach to genetic counseling for patients and at-risk family members.

HSP and deafness: Neurocristopathy caused by a novel mosaic SOX10 mutation.

OBJECTIVE: To identify the underlying genetic cause in 2 sisters affected with progressive lower extremity spasticity, neuropathy, and early-onset deafness. METHODS: Whole-exome sequencing was performed, and segregation testing of variants was investigated using targeted Sanger sequencing. An inherited paternal mosaic mutation was further evaluated through quantitative analysis of the ratio of mutant vs wild-type allele in genomic DNA from various tissues, including blood, dermal fibroblasts, and saliva. RESULTS: A novel heterozygous nonsense mutation (c.1140C>A; p.Y380X) in SOX10 was identified in the affected sisters. Paternal mosaicism was suspected based on a small chromatogram peak, which was less than the heterozygous peak of the mutated allele. Consistent with mosaicism, the mosaic paternal samples had notable variability in the ratio of mutant vs wild-type allele in various tissues (compared with the fully heterozygous daughter), with the highest paternal mutant levels in saliva (32.7%) and lowest in dermal fibroblasts (13.9%). Targeted clinical re-examination of the father revealed a sensorimotor neuropathy that was previously clinically unrecognized. CONCLUSIONS: These findings expand the phenotypic spectrum of SOX10-related neurocristopathy. Mutations in SOX10 should be considered in patients presenting with a complicated form of hereditary spastic paraplegia that includes neuropathy and deafness. Diagnostic workup may be complicated, as SOX10 mutations can present in a mosaic state, with a mild clinical manifestation.

Effectiveness of exome and genome sequencing guided by acuity of illness for diagnosis of neurodevelopmental disorders.

Neurodevelopmental disorders (NDDs) affect more than 3% of children and are attributable to single-gene mutations at more than 1000 loci. Traditional methods yield molecular diagnoses in less than one-half of children with NDD. Whole-genome sequencing (WGS) and whole-exome sequencing (WES) can enable diagnosis of NDD, but their clinical and cost-effectiveness are unknown. One hundred families with 119 children affected by NDD received diagnostic WGS and/or WES of parent-child trios, wherein the sequencing approach was guided by acuity of illness. Forty-five percent received molecular diagnoses. An accelerated sequencing modality, rapid WGS, yielded diagnoses in 73% of families with acutely ill children (11 of 15). Forty percent of families with children with nonacute NDD, followed in ambulatory care clinics (34 of 85), received diagnoses: 33 by WES and 1 by staged WES then WGS. The cost of prior negative tests in the nonacute patients was $19,100 per family, suggesting sequencing to be cost-effective at up to $7640 per family. A change in clinical care or impression of the pathophysiology was reported in 49% of newly diagnosed families. If WES or WGS had been performed at symptom onset, genomic diagnoses may have been made 77 months earlier than occurred in this study. It is suggested that initial diagnostic evaluation of children with NDD should include trio WGS or WES, with extension of accelerated sequencing modalities to high-acuity patients.