Thin basement membrane nephropathy is a primary glomerulonephritis caused by abnormalities of type IV collagen and thinning of the glomerular basement membrane. Patients typically present with episodes of intermittent gross hematuria and flank pain, often triggered by upper respiratory tract (URT) infections or exercise. Urinalysis shows persistent microhematuria and sometimes proteinuria. Kidney biopsy is required for diagnosis, showing diffuse thinning of the glomerular basement membrane. While the disease generally has an excellent prognosis and often does not require treatment, patients with proteinuria should be treated with ACE inhibitors to slow progression.
- Prevalence: 5–9% 
Epidemiological data refers to the US, unless otherwise specified.
- Hereditary (usually autosomal dominant) or sporadic
- Abnormalities of type IV collagen cause thinning of the glomerular basement membrane → transient ruptures of glomerular capillary wall → hematuria
- Usually asymptomatic
- Episodic gross hematuria, possibly in combination with flank pain may occur, typically following an upper respiratory tract infection or exercise. 
- Other symptoms of nephritic syndrome (e.g., hypertension) can occur (especially in adults).
- Very rarely progresses to end-stage renal disease
Diagnosis is typically based on clinical presentation and a family history of benign hematuria. Renal biopsy is reserved for patients with signs of progressive disease (e.g., proteinuria, hyperkalemia) and unclear family history.
- Usually only persistent microhematuria
- Possible episodic gross hematuria, potentially associated with hypercalciuria and hyperuricosuria
- Minor proteinuria is possible, especially in adults
- Light microscopy: no abnormalities
- Electron microscopy: diffuse thinning of the glomerular basement membrane
- Isolated hematuria does not require treatment.
- ACE inhibitors/AT-II antagonists in patients with proteinuria > 500–1,000 mg/day