Amyloidosis, primary: A disorder of plasma cells (special white blood cells that produce antibodies), this is one of a group of diseases (called amyloidosis) in which protein deposits (amyloid) accumulate in one or more organ systems in the body. Primary amyloidosis is the most common type of amyloidosis in many countries including the U.S.
The protein deposits in primary amyloidosis are made up of immunoglobulin light chain proteins. These light chain proteins are created in the bone marrow by malfunctioning plasma cells. Primary amyloidosis occurs by itself (in isolated form) and is not associated with any other disease.
The organs most often involved in primary amyloidosis include the heart, kidneys, nervous system, and gastrointestinal tract. Amyloid deposits in these organs can cause shortness of breath, fatigue, edema (swelling of ankles and legs), dizziness upon standing, a feeling of fullness in the stomach (especially after eating), diarrhea, weight loss, enlarged tongue, and numbness of the legs and arms. In the laboratory, a great excess of protein is found in the urine.
Primary amyloidosis is usually treated with chemotherapy. The drug melphalan in pill form has for years been the key chemotherapeutic agent for primary amyloidosis. More aggressive treatment is under study with intravenous melphalan plus return of the patient's own bone marrow stem cells. Stem cells are the "parent" cells formed in the bone marrow from which all blood cells develop. This approach aims to eliminate the malfunctioning plasma cells which make the amyloid light chains and to re-create a wholly healthy bone marrow.