thin glomerular basement membrane (GBM) disease, an inherited type IV collagen abnormality that causes thinning of the GBM and results in hematuria. The disorder may affect up to 5% of the population, and 30% to 50% of patients report a family history of hematuria. The disease is characterized by microscopic or macroscopic hematuria that may be first discovered in young adults. Diagnosis is usually based on the history of persistent hematuria, normal kidney function, and positive family history of hematuria without kidney failure; biopsy is not typically required. Long-term prognosis for kidney function is excellent, with rare progression to chronic kidney disease (CKD).