An 8-year-old girl is evaluated for persistent asymptomatic microscopic hematuria found on routine screening. Her father has similar findings. Renal function is normal and there is no hearing loss. Biopsy electron microscopy shows uniform thinning of the glomerular basement membrane. The most likely diagnosis is:

• A Alport syndrome
• B IgA nephropathy
• C Thin basement membrane lesion (benign familial hematuria) ✓
• D Post-infectious glomerulonephritis

Explanation

Thin basement membrane lesion is caused by heterozygous COL4A3 or COL4A4 mutations with autosomal dominant transmission, producing diffuse GBM thinning (below approximately 250 nm, normally 300 to 400 nm in adults). It runs a benign course with lifelong isolated hematuria and preserved renal function. The father-to-daughter transmission excludes X-linked Alport syndrome, and absence of sensorineural deafness, lenticonus, and GBM splitting further separates it from Alport. IgA nephropathy shows mesangial IgA deposits on immunofluorescence.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.