Renal complications in patients with diabetes mellitus associated with an A to G mutation of mitochondrial DNA at the 3243 position of leucine tRNA

The substitution of guanine for adenine at position 3243 of the leucine tRN A gene of mitochondrial DNA was originally described in association with ME LAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-lik e episodes). Diabetes mellitus associated with the mutation (mitochondrial diabetes) is a different phenotype from MELAS. We identified 11 patients wi th the mutation among 385 Japanese diabetic patients: two had MELAS and nin e had mitochondrial diabetes. We present data on a male patient with mitoch ondrial diabetes who developed the nephrotic syndrome at the age of 23. Lig ht microscopy revealed mesangial expansion, PAS-positive deposits and segme ntal sclerosis in the glomeruli. Scattered mesangial electron-dense deposit s and thickening of the basement membrane were found on electron microscopy , suggesting that diabetic glomerulosclerosis accompanied by focal glomerul osclerosis (FGS). Mitochondrial diabetes may pre-dispose patients to renal complications, including forms of glomerulonephritis, such as FGS. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.