AMYLOIDOSIS

Introduction

Amyloidosis is not a specific disease but the term for a group of conditions in which an abnormal substance called amyloid is deposited throughout the body. The tissues which may be affected are nerves, heart, kidneys, tongue, intestines, liver, spleen, eyes, thyroid, skin and brain. In a minority of patients there will be very localized amyloid deposits. These usually occur in the lungs, larynx, skin, bladder or tongue.

Causes

Amyloidosis in is called primary when the amyloid protein, AL, is produced directly by the plasma cells cells. It is similar to myeloma and the two shade into each other. In secondary amyloidosis the link between the initial illness, for example rheumatoid arthritis, and the occurrence of amyloidosis is indirect. In these cases the production of amyloid (AA) probably arises from some form of immune process.

Common causes of secondary amyloidosis include infection with a type of bacteria called mycobacteria (this group includes the TB bacterium) and autoimmune diseases such as rheumatoid arthritis and Crohn’s disease.

Signs and symptoms

The signs and symptoms depend very much on which tissue(s) have deposits of amyloid protein. The most common features are weight loss, fatigue, kidney failure, congestive heart failure, weakness of the wrists and hands (called carpal tunnel syndrome) and nerve problems in the limbs (peripheral neuropathy). Enlargement of the tongue may lead to difficulty in speaking and swallowing and internal involvement may cause diabetes. A facial rash (purpura), especially around the eyes, occurs in about 15% of patients.

Diagnosis

Diagnosis depends on the demonstration of amyloid deposits in a tissue biopsy. The tissue can usually be obtained by using a fine needle. If the organ affected is inaccessible, for example the heart, diagnosis can often be made by simply taking a small sample from the pad of fat on the abdomen or from within the rectum.

Treatment

Drug treatment, as for myeloma, may help to reduce the level of amyloid protein and thus the symptoms. It is not a cure and will not eliminate the underlying disease.

The main drugs used in treatment of amyloidosis are melphalan and prednisolone, which are drugs also used in treatment of multiple myeloma.

Treatment of amyloidosis is largely aimed at treating the effects on other organs or tissues. Thus, patients with severe heart or kidney disease, whose amyloidosis has been brought under control, may require a transplant. A liver transplant is normally only considered for patients with hereditary amyloidosis but it may offer a cure.

Prognosis

Amyloidosis is a general term for a group of conditions with different underlying causes and which behave different clinically. For this reason, it is not possible to make any general comments about the likely outlook. Patients should discuss their illness in detail with their specialist. Also for this reason patients should not be surprised if their treatment and the advice they receive are different from those of other patients they may meet who have amyloidosis.