A 24-year-old Asian man who is a graduate student is discovered to have asymptomatic microscopic hematuria during a routine examination for a sports-related injury. The BP is 118/72 mmHg. His body mass index (BMI) is 33 kg/m 2 . The remainder of the history and physical examination is unremarkable. The serum creatinine level is 0.78 mg/dl. The urine sediment reveals 10–15 erythro- cytes per high power field, of which 50% are dys- morphic. A spot urine albumin-to-creatinine ratio is 39 mg/g. The fasting blood glucose is 110 mg/dl. Which ONE of the following lesions is MOST likely to be found on renal biopsy? A. FSGS B. Thin basement membrane nephropathy C. Minimal change disease D. IgA nephropathy E. Early diabetic glomerulosclerosis

Answer D: IgA nephropathy
This young Asian man has asymptomatic glomerular dysmorphic hematuria and increased albuminuria. He has no evidence of a systemic disease, his blood pressure is normal, and his kidney function is normal. Based on large scale kidney biopsy series in subjects of similar demographics, IgA nephropathy (option D) is the most common lesion encountered. Although he is obese, focal segmental glomerulosclerosis (option A) would be unlikely given the relatively low level of albuminuria and the presence of glomerular hematuria. Thin basement membrane nephropathy (option B) is possible, but is less likely to be found when compared to IgA nephropathy. Minimal change disease (option C) is unlikely due to the low level of albuminuria and nephritic presentation. Early diabetic glomerulosclerosis (option E) is unlikely to cause dysmorphic hematuria and increased albuminuria.