Thin basement membrane disease is, along with IgA nephropathy, the most common cause of hematuria without other symptoms. The only abnormal finding in this disease is a thinning of the

basement membrane The basement membrane is a thin, pliable sheet-like type of extracellular matrix that provides cell and tissue support and acts as a platform for complex signalling. The basement membrane sits between Epithelium, epithelial tissues including mesot ...

of the glomeruli in the kidneys. Its importance lies in the fact that it has a benign

prognosis Prognosis (Greek: πρόγνωσις "fore-knowing, foreseeing") is a medical term for predicting the likely or expected development of a disease, including whether the signs and symptoms will improve or worsen (and how quickly) or remain stabl ...

, with patients maintaining a normal kidney function throughout their lives.

Signs and symptoms

Most patients with thin basement membrane disease are incidentally discovered to have

microscopic hematuria The microscopic scale () is the scale of objects and events smaller than those that can easily be seen by the naked eye, requiring a lens or microscope to see them clearly. In physics, the microscopic scale is sometimes regarded as the scale bet ...

on urinalysis. The

blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...

, kidney function, and the urinary protein excretion are usually normal. Mild proteinuria (less than 1.5 g/day) and

hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...

are seen in a small minority of patients. Frank hematuria and loin pain should prompt a search for another cause, such as kidney stones or

loin pain-hematuria syndrome Loin pain hematuria syndrome (LPHS) is the combination of debilitating unilateral or bilateral flank pain and microscopic or macroscopic amounts of blood in the urine that is otherwise unexplained. Loin pain-hematuria syndrome (LPHS) is a poorly ...

. Also, there are no systemic manifestations, so presence of

hearing impairment Hearing loss is a partial or total inability to hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to acquire spoken l ...

or visual impairment should prompt a search for

hereditary Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic inform ...

nephritis such as Alport syndrome.

Genetics

The molecular basis for thin basement membrane disease has yet to be elucidated fully; however, defects in type IV collagen have been reported in some families. Some individuals with TBMD are thought to be carriers for genes that cause Alport syndrome.

Diagnosis

Thin basement membrane disease must be differentiated from the other two common causes of

glomerular ''Glomerulus'' () is a common term used in anatomy to describe globular structures of entwined vessels, fibers, or neurons. ''Glomerulus'' is the diminutive of the Latin ''glomus'', meaning "ball of yarn". ''Glomerulus'' may refer to: * the filter ...

hematuria, IgA nephropathy and Alport syndrome. The history and presentation are helpful in this regard: * In Alport syndrome, there is often a family history of kidney failure, which may be associated with

. Also, males tend to be more affected as Alport syndrome is X-linked in most cases. * In IgA nephropathy, episodes of frank hematuria are more common, and a family history is less common. A kidney biopsy is the only way to diagnose thin basement membrane disease. It reveals thinning of the

glomerular basement membrane The glomerular basement membrane of the kidney is the basal lamina layer of the glomerulus. The glomerular endothelial cells, the glomerular basement membrane, and the filtration slits between the podocytes perform the filtration function of the ...

from the normal 300 to 400 nanometers (nm) to 150 to 250 nm. However, a biopsy is rarely done in cases where the patient has isolated

, normal kidney function, and no proteinuria. The prognosis is excellent in this setting unless the clinical manifestations progress, as occurs in most males and some females with Alport syndrome and many patients with IgA nephropathy.

Treatment

Most patients with thin basement membrane disease need only reassurance. Indeed, this disease was previously referred to as "benign familial hematuria" because of its usually benign course. Angiotensin converting enzyme inhibitors have been suggested to reduce the episodes of hematuria, though controlled studies are lacking. Treating co-existing hypercalciuria and hyperuricosuria will also be helpful in reducing hematuria. The molecular basis for thin basement membrane disease has yet to be elucidated fully; however, defects in the gene encoding the a4 chain of type IV collagen have been reported in some families.

Prognosis

Overall, most people with thin basement membrane disease have an excellent

. Some reports, however, suggest that a minority might develop

. Thin basement membrane disease may co-exist with other kidney diseases, which may in part be explained by the high prevalence of thin basement membrane disease.

References

External links

{{DEFAULTSORT:Thin Basement Membrane Disease Kidney diseases