What are amyloidoses? |

Related conditions:

Multiple myeloma

Definition:


Amyloidoses are a class of illnesses in which fibrillar protein deposits form throughout the body. Immunoglobulin-related (AL) amyloidosis, a disorder sometimes caused by cancerous antibody-secreting plasma cells, results when misfolded antibody chains form deposits that impair function of the heart, kidneys, and other organs.

Risk factors: There are no known risk factors.

Etiology and the disease process: In a minority of patients with multiple myeloma, antibody fragments that are produced by malignant plasma cells form insoluble fibrillar protein deposits. Deposits can form in many organs but are most often found in the kidney, heart, liver, and peripheral and autonomous nervous systems. These deposits ultimately lead to death, most commonly via heart disease and renal failure.

Incidence: The overall incidence of AL amyloidosis is approximately 1 in 100,000 people per year. Men are more likely than women to develop AL amyloidosis. Approximately 15 percent of patients with multiple myeloma develop AL amyloidosis, but cases of myeloma-associated amyloidosis make up a small fraction of AL amyloidosis cases.

Symptoms: Symptoms depend on the organs involved and vary among patients. Common symptoms include peripheral edema, proteinuria, hepatomegaly, hypotension, shortness of breath, irregular heartbeat, purpura, macroglossia, carpal tunnel syndrome, and peripheral neuropathy.

Screening and diagnosis: Many amyloidoses are diagnosed by Congo Red staining of tissues biopsied from subcutaneous fat pads, rectal mucosa, bone marrow, or other sources. Once diagnosis of amyloidosis is established, a free light chain blood test is performed to confirm immunoglobulin chains as the cause of amyloid deposits.

Treatment and therapy: Current treatments for amyloidosis parallel those used for multiple myeloma. Melphalan plus predisone reduces the number of malignant plasma cells and levels of circulating immunoglobulin light chains. This is often followed by autologous stem cell transplantation, aimed at rebuilding healthy bone marrow. In some patients, treatment results in a temporary resorption of amyloid fibrils and improvement in organ function. The malignant plasma cells are not completely eradicated, however, and remission is the usual course. IDOX (4′-deoxy-4′-iododoxorubicin), a drug that binds to amyloid fibrils and promotes their disassembly, has shown promise in early trials.

Prognosis, prevention, and outcomes: Prognosis for patients with AL amyloidosis depends on which organs are affected. Patients with cardiac involvement have the worst prognosis, while patients with involvement limited to other organs have longer median survival times. There is no known way to prevent amyloidosis.

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