Amyloidosis

Amyloidosis is a group of conditions where proteins called amyloid deposit in tissues and organs of the body.  Deposition may be localized, where amyloid builds up in a single organ, or systemic, where several organs are affected and interfere in its normal function. 

Classification

Amyloidosis can be classified into three major types, depending on the kind of protein that accumulates in the tissues.  Primary amyloidosis (AL) is the most common form, which occurs when the cells of the bone marrow produce too much of a certain portion of antibodies called light chain.  These build up in the bloodstream and eventually accumulate in the tissues.

Secondary amyloidosis (AA) occurs in association with other illnesses like multiple myeloma, chronic inflammatory diseases such as rheumatoid arthritis, chronic infections like tuberculosis and osteomyelitis (bone infection).  AA proteins are deposited in the organs and treatment of this type of amyloidosis is directed at treating the underlying disease, which may stop the progression of amyloidosis.

Familial or hereditary amyloidosis (ATTR) is caused by the protein transthyretin or ATTR from the liver.  This is an autosomal dominant trait which means that the persons affected with this condition will have a 50% chance of passing it on to their offspring. 

Localized amyloidosis results from the deposition of amyloid proteins in specific organs of the body.  Amyloid deposits may be found in the brain of patients with Alzheimer’s disease and in the pancreas in patients with type 2 diabetes.  Beta-2 microglobulin amyloidosis affects patients who are on dialysis.  The amyloid deposits are beta-2 microglobulin proteins.

Pathophysiology

Amyloidosis is thought to be caused by damage in the body from free radicals and oxygen.  These build up and may later trigger the disease.  The hereditary form is a result of genetic changes, leading to the production of abnormal proteins.

Risk Factors

Individuals at high risk of developing amyloidosis include men, age 50 and above, other diseases (ie, multiple myeloma, Waldenstrom’s macroglobulinemia, inflammatory bowel disease, tuberculosis, Mediterranean fever, among others), family history, prolonged dialysis. 

Clinical Features

The signs and symptoms in patients with amyloidosis depend on the organs that have been affected, which include the kidneys, heart, gastrointestinal tract, liver, skin, nerves, joints, and lungs.  The signs and symptoms may be the following: irregular heart beat, kidney failure, diarrhea or constipation, enlarged liver, diminished function of the endocrine glands like the adrenals, macroglossia or enlarged tongue, difficulty in breathing, bleeding problems, purpura or bleeding around the eyes, and shortness of breath.

Diagnosis

Confirmatory diagnosis is through tissue diagnosis.  A tissue sample from the affected organ is studied under the microscope to test for amyloid.  In systemic amyloidosis, biopsy of the fat under the skin in the abdominal area may be performed.  The tissue sample is stained with the Congo Red Dye and the amyloid is confirmed when it stains dark red. 

Treatment

There is currently no treatment for amyloidosis.  Treatment is focused at the treatment of the underlying disease and in reducing the production of amyloid.  Chemotherapy drugs like Alkeran and steroids have shown to be effective in the management of amyloidosis.  Stem cell transplantation may also be considered.  For the relief of edema and fluid retention, diuretics may be given.  If the patient presents with arrhythmia or an abnormal heart beat, anti-arrhythmic medications may be initiated or a pacemaker may be implanted.  If kidney failure ensures, the patient may be put on dialysis.