Thin basement membrane disease (also known as benign familial hematuria and thin basement membrane nephropathy) is, along with IgA nephropathy, the most common cause of asymptomatic hematuria (blood in the urine). The only abnormal finding in this disease is a thinning of the basement membrane of the glomeruli in the kidneys. Most patients with TBM maintain a normal kidney function throughout their lives.
TBM usually does not have any symptoms a person can feel. Usually the disease is diagnosed when a small amount of blood (microscopic hematuria) is found using a urine sample. Most patients with thin basement membrane disease are incidentally discovered to have microscopic hematuria on urinalysis. The blood pressure, kidney function and the urinary protein excretion are usually normal. Mild proteinuria (protein in the urine – less than 1.5g/day) and high blood pressure are seen in a small minority of patients.
In most cases TBM is not treated, as most people with the disease maintain normal kidney function. Most people with TBM have their kidney function followed by their doctor.