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PubMed2000

2-Methylbutyryl-coenzyme A dehydrogenase deficiency: a new inborn error of L-isoleucine metabolism.

An 4-mo-old male was found to have an isolated increase in 2-methylbutyrylglycine (2-MBG) and 2-methylbutyrylcamitine (2-MBC) in physiologic fluids. In vitro oxidation studies in cultured fibroblasts using 13C- and 14C-labeled branched chain amino acids indicated an isolated block in 2-methylbutyryl-CoA dehydrogenase (2-MBCDase). Western blotting revealed absence of 2-MBCDase protein in fibroblast extracts; DNA sequencing identified a single 778 C>T substitution in the 2-MBCDase coding region (778 C>T), substituting phenylalanine for leucine at amino acid 222 (L222F) and absence of enzyme activity for the 2-MBCDase protein expressed in Escherichia coli. Prenatal diagnosis in a subsequent pregnancy suggested an affected female fetus, supporting an autosomal recessive mode of inheritance. These data confirm the first documented case of isolated 2-MBCDase deficiency in humans.

Amino Acid Metabolism, Inborn Errors↗

PubMed1998

Microcephaly with chorioretinal degeneration.

PURPOSE: To describe the ophthalmologic findings and electroretinograms in patients with microcephaly and chorioretinal degeneration. METHODS: We reviewed the hospital records of 20 patients with microcephaly that was not part of a recognizable syndrome prior to initial referral to the institutional consultative practice of one of the authors (RGW). Twelve patients, all from separate families, were diagnosed as having microcephaly with chorioretinopathy. Ten of these patients had ISCEV-standard electroretinograms (ERG). RESULTS: No family history of microcephaly or retinal degeneration was found in any of our patients. Three patients had another family member with mental retardation. Three of the 12 were compatible with the autosomal dominant form of microcephaly with chorioretinopathy (MIM 156590), possibly as a new mutation. Eight patients, who had fundus findings of retinitis pigmentosa, were similar to the autosomal recessive form of microcephaly with chorioretinal degeneration (MIM 251270). The ERGs were moderately to severely subnormal for responses of both rods and cones. The retinal findings varied from no pigmentary changes, pigment clumping and bone spicules, pigmentary granularity, bull's eye maculopathy, choroidal and retinal atrophy, to lacunar depigmentation. Mental retardation was mild to profound. The abnormal findings from MRI/ CT brain scans (8 patients) were cerebellar atrophy (2), agenesis of cerebellar vermis (1), cortical atrophy (1), and pachygyria (1). Dysmorphic features were present in most patients. Chromosome studies were normal, except for one patient with ring chromosome 14. CONCLUSIONS: Although the patients reviewed in this study represent a heterogeneous group of disorders, ocular abnormalities, especially retinal degeneration, are frequent among patients with microcephaly.

Adolescent↗