The width of the basement membrane does not influence clinical presentation or outcome of thin glomerular basement membrane disease with persistent hematuria.

Thin basement membrane disease (TBMD) typically presents with persistent microscopic hematuria, and is usually defined as a glomerular basement membrane (GBM) thickness < 250 nm. Previous studies showed that neither the degree of thinning nor the extent of the abnormality correlate with the patient's clinical presentation or prognosis. To further define this, we enrolled a study group of 41 patients with isolated microscopic hematuria and a normal renal biopsy, except those with a GBM thickness of 250-320 nm, and compared them with 33 patients with traditional TBMD. We found no difference in baseline demographic or clinical parameter between the groups. After follow-up averaging 110 months, there was no significant difference in the risk of detectable or overt proteinuria, hypertension, or impaired renal function between the groups. By the end of the study, only five patients from the study group and four from the TBMD group had no outcome event. By Cox regression analysis, independent predictors of overt proteinuria were male gender, age at biopsy, baseline renal function, proteinuria, and hypertension. Age at biopsy was the only independent predictor for hypertension, and baseline proteinuria was the only independent predictor for impaired renal function. GBM thickness did not predict any outcome event. Hence, lifelong follow-up is advised, as the clinical features and prognosis of these patients with persistent microscopic hematuria and marginally thin GBM are similar to traditional TBMD.