OBJECTIVE To evaluate renal structure in a child with Donohue syndrome (leprechaunism), who at 10 yr of age was noted to have hypertension, microalbuminuria, and enlarged kidneys, a renal biopsy was performed. METHODS The renal biopsy tissue was evaluated by light and electron microscopy with standard stereological techniques to measure glomerular volume, glomerular basement membrane width, fractional mesangial volume, and peripheral capillary filtering surface density. RESULTS On renal biopsy, there was a marked increase in glomerular volume, glomerular basement width, and mesangial volume, findings similar to those seen in patients with diabetic nephropathy. CONCLUSIONS This patient with marked insulin resistance associated with Donohue syndrome demonstrates renal and glomerular enlargement and morphometric glomerular changes similar to those seen in patients with diabetic nephropathy. In unusual syndromes with hyperglycemia and hyperinsulinemia, renal structural and functional changes typical of traditional diabetes mellitus may be seen.