Amyloidosis is an uncommon disease in which a substance called amyloid, composed of fibrous protein, accumulates in tissues and organs, including the liver, kidneys, tongue, spleen, and heart.

 

Causes

Amyloidosis may occur for no known reason, when it is called primary; more commonly, it is a complication of some other disease, when it is called secondary. Conditions that may lead to amyloidosis include rheumatoid arthritis, multiple myeloma (a cancer of bone marrow), tuberculosis, and some other long-standing infections, such as chronic osteomyelitis (bone infection). Exactly why amyloid is deposited in any of these circumstances is not known.

 

Symptoms and signs

The symptoms and signs of amyloidosis vary, depending on which part of the body is involved.

 

Affected organs typically become enlarged. Accumulation of amyloid in the heart may result in arrhythmias (disturbances of the heartbeat) and heart failure (reduced pumping efficiency). If the stomach and intestines are affected, symptoms such as diarrhea may develop and lining of these organs may become ulcerated. In some cases, the joints are affected causing arthritis.

 

Primary amyloidosis is often characterized by deposits of amyloid in the skin. Slightly raised, waxy spots appear, usually clustered around the armpits, groin, face, and neck.

 

Some rare forms of amyloidosis are inherited. These forms of the disease tend to involve the nervous system. Symptoms include peripheral neuropathy, postural hypotension, urinary or fecal incontinence, and reduced sweating. Death may occur as a result of renal failure caused by deposits of amyloid in the kidneys.

 

Diagnosis and treatment

Diagnosis depends on microscopic and biochemical examination of a biopsy sample of tissue. Affected organs usually have a rubbery consistency and a waxy, pink, or gray appearance.

 

There is no treatment, but secondary amyloidosis may be arrested or even reversed when the underlying disorder is treated.