A healthy 22-year-old man found to have persistent microscopic hematuria on routine screening has normal blood pressure, normal creatinine, no hearing loss, and a family history of isolated hematuria in his father. Renal biopsy shows normal light microscopy and immunofluorescence; electron microscopy shows uniform attenuation of the glomerular basement membrane to approximately 180 nm without splitting or lamellation. The most likely diagnosis is:
- A Alport syndrome, heterozygous COL4A5 carrier state
- B Thin basement membrane lesion (benign familial hematuria) ✓
- C IgA nephropathy, early stage
- D Focal segmental glomerulosclerosis
Correct answer: B. Thin basement membrane lesion (benign familial hematuria)
Explanation
Isolated hematuria with uniformly thinned GBM (less than roughly 250 nm in adults), preserved renal function, absence of extrarenal features, and autosomal dominant transmission define thin basement membrane lesion, usually from heterozygous COL4A3 or COL4A4 mutations. Alport syndrome shows basket-weave splitting of the GBM plus sensorineural deafness, and both IgA nephropathy and FSGS have abnormal light microscopy or immunofluorescence findings.
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.