Clinical and pathologic features of focal segmental glomerulosclerosis with mitochondrial tRNALeu(UUR) gene mutation

Clinical and pathologic features of focal segmental glomerulosclerosis with mitochondrial tRNALeu(UUR) gene mutation.BackgroundSeveral families have been described in which an A to G transition mutation at position 3243 (A3243G) of the mitochondrial DNA (mtDNA) is associated with focal and segmental glomerulosclerosis (FSGS). However, the prevalence, clinical features, and pathophysiology of FSGS carrying mtDNA mutations are largely undefined.MethodsAmong 11 biopsy-proven primary FSGS patients of unknown etiology, we examined seven FSGS patients to determine whether any of the clinical and pathological features of FSGS were associated with an A3243G mtDNA mutation. In four subjects in whom the A3243G mtDNA mutation was discovered in blood leukocytes, as well as in urine sediments, we retrospectively reviewed the medical records and re-evaluated the renal biopsy specimen using light and electron microscopy. We further screened the patient's family members for the presence and degree of heteroplasmy for this mtDNA mutation and obtained medical histories that were consistent with mitochondrial cytopathy.ResultsThe four individuals identified with the A3243G mtDNA mutation were female. Proteinuria was diagnosed in these individuals during a routine annual health checkup in their teenage years. None of the patients showed any symptoms related to mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode, whereas diabetes mellitus in two of the patients and a hearing disturbance in one patient became manifest within a 3- to 13-year follow-up period. Strict maternal transmitted inheritance was confirmed by pedigree studies in all of these patients. Steroid therapy was ineffective in all four patients. In two of these patients, renal function declined slowly to end-stage renal failure. Histologic examination of biopsy specimens revealed that glomeruli were not hypertrophied, while electron microscopic examination identified severely damaged, multinucleated podocytes containing extremely dysmorphic abnormal mitochondria in all patients.ConclusionsFSGS may belong to the spectrum of renal involvement in A3243G mtDNA mutation in humans. Severely injured podocytic changes containing abnormal mitochondria may explain the pathogenesis of FSGS in association with the A3243G mtDNA mutation

Molecular analysis of holocarboxylase synthetase deficiency: a missense mutation and a single base deletion are predominant in Japanese patients

AbstractHolocarboxylase synthetase (HCS) deficiency is an inherited disease of biotin metabolism characterized by a unique pattern of organic aciduria, metabolic acidosis, and skin lesions. By analysis of five patients in four unrelated families, two mutations were identified: a transition from T to C which causes an amino-acid substitution of proline for leucine at position 237 (L237P) and a single deletion of guanine (delG 1067) followed by premature termination. One patient was homozygous for the L237P mutation, three patients in two families were compound heterozygotes of the missense and deletion alleles, and the other patient was heterozygous for the L237P mutation. Inheritance was successfully demonstrated in all of the patients' families by a modified PCR followed by restriction enzyme digestion. The two mutations accounted for seven of eight mutant alleles, while neither mutation was detected in 108 normal healthy Japanese children (216 alleles). Transient expression in cultured fibroblasts from a patient showed that the L237P mutation was responsible for decreased HCS activity. These results suggest that the L237P and delG1067 mutations are frequent disease-causing mutations in Japanese patients with HCS deficiency. This PCR-based technique may therefore be useful for detecting mutations among Japanese patients