Summary

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.

Epidemiology

Prevalence: 5–9%

Epidemiological data refers to the US, unless otherwise specified.

Etiology

Hereditary (usually autosomal dominant) or sporadic

Pathophysiology

Abnormalities of type IV collagen cause thinning of the glomerular basement membrane → transient ruptures of glomerular capillary wall → hematuria

Clinical features

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

Diagnostics

Diagnosis is usually assumed in patients based on the presentatation and a family history of benign hematuria. Renal biopsy is reserved for cases in which signs of progression (e.g., proteinuria, hyperkalemia) occur or if the family history is unclear.

Urinalysis
- Usually only persistent microhematuria
- Possible episodic gross hematuria, potentially associated with hypercalciuria and hyperuricosuria
- Minor proteinuria is possible, especially in adults
Renal biopsy
- Light microscopy: no abnormalities
- Electron microscopy: diffuse thinning of the glomerular basement membrane

Treatment

Isolated hematuria does not require treatment.
ACE inhibitors/AT-II antagonists in patients with proteinuria > 500–1000 mg/day