IgA nephropathy in a girl with mitochondrial disease.

Mitochondrial renal disease is one of the important causes of end-stage renal disease in children and its incidence may be underestimated. We here describe the case of a 13-year-old girl who was diagnosed with mitochondrial disease (MD) accompanied by IgA nephropathy (IgAN). She presented with persistent proteinuria, short stature, and hearing defect, and her younger sister had the same symptoms. Renal biopsy indicated mild focal segmental mesangial proliferation with dominant mesangial IgA deposition on immunofluorescence. Electron microscopy showed marked proliferation of abnormal mitochondria in the proximal tubular cells. Enzyme activity of the mitochondrial respiratory chain complex I and IV in cultured skin fibroblasts was significantly decreased. This case indicated the possible co-occurrence of IgAN and MD. Underlying MD should be considered in patients with urine abnormalities, especially in those with multiple organ involvement.