Kidney Disease: Thin-Basement-Membrane Nephropathy

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Benign Familial Hematuria, also known as Thin-Basement-Membrane

Nephropathy, is a non-progressive genetic kidney disease that usually

begins during childhood.

The disorder is characterized by the presence of red blood cells in the

urine (hematuria). Blood cells enter the urine when the glomerular

basement membrane (GBM) breaks down.

The GBM is made of a meshwork of proteins and other constituents. The

GBM forms the boundary between the capillaries in the kidneys and the

urine. Across it, water and other small molecules from the blood are

filtered.

In Thin-Basement-Membrane syndrome, the GBM is thin, and sometimes

breaks. When it does, it causes blood to appear in the urine. However it

seems to repair itself without any ill effect, as thin GBM disease

almost never causes serious trouble.

The blood in the urine may be present in microscopic amounts

(microscopic hematuria) and not visible to the eye, present in small

amounts that give the urine a " cloudy " or " smoky " appearance, or easily

visible.

Many individuals with the disorder have abnormalities of the kidney's

glomeruli, the clusters of small blood vessels (capillaries) that

normally filter the blood passing through the kidneys (glomeruli

filtration).

In such cases, the membrane (basement membrane) supporting the loops of

capillaries that make up the renal glomeruli may be abnormally thin.

Benign Familial Hematuria may be inherited as an autosomal dominant

genetic trait.

In nephritis disease of the kidney, the GBM is thickened and scarred.

This disease has been discovered relatively recently and unfortunately

remains poorly understood. It often causes a protein leak and nephrotic

syndrome. Deterioration to kidney failure is common.

Normal urine should contain almost no protein. In nephrotic syndrome the

leak is large enough so that the levels of protein in the blood fall.

Symptoms of nephrotic syndrome are usually severe swelling in the ankles

and legs. Extra fluid may also accumulate in the abdomen and around the

face, especially overnight.

Most ankle swelling is caused by other things ­ nephrotic syndrome is a

rare cause. Urine tests and blood samples are

required to prove the diagnosis of nephrotic syndrome.

The protein leak can sometimes make the urine frothy. Some people feel

tired. The syndrome is usually found by abnormal urinalysis results. The

most important test however is a renal biopsy. This test is designed to

take a small piece of kidney to look at under the microscope.