A case of mitochondrial cytopathy with a typical point mutation for MELAS,presenting with severe focal-segmental glomerulosclerosis as main clinicalmanifestation

A 27-year-old female with short stature and mild hearing loss was diagnosed as having focal-segmental glomerulosclerosis by renal biopsy at our hospit al. One year later she developed progressive renal dysfunction and cardiac failure and was admitted again to our hospital for evaluation. Though her o nly neurological disorder was mild hearing loss, her short stature and elev ated lactate and pyruvate values in cerebrospinal fluid suggested mitochond rial cytopathy. A muscle biopsy specimen of the left biceps brachii, using modified Gomori trichrome stain, showed a typical image of ragged-red fiber s, and an increased number of giant mitochondria with paracrystalline inclu sions were visible by electron microscopy. Mitochondrial DNA from the skele tal muscle showed an A-to-G transition at 3243 of transfer RNA(Leu(UUR)), t he common point mutation for mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes. These data confirmed the diagnosis of atypical mitochondrial cytopathy with renal and heart involvement. Mitochon drial cytopathies are often associated with hypertrophic cardiomyopathy but rarely with renal disease. Among the few reported cases with associated re nal disease, most included renal tubular disorders; few cases with focal gl omerular sclerosis are known. The present case of atypical mitochondrial cy topathy was characterized by a unique clinical course and rare complication s with focal-segmental glomerulosclerosis.