Amyloidosis (am-uh-loi-DO-sis) is a rare disease that occurs when a substance called amyloid builds up in your organs. Amyloid is an abnormal protein that is usually produced in your bone marrow and can be deposited in any tissue or organ. Amyloidosis can affect different organs in different people, and there are different types of amyloid. Amyloidosis frequently affects the heart, kidneys, liver, spleen, nervous system and digestive tract. Severe amyloidosis can lead to life-threatening organ failure.
The modern way of classifying amyloidosis is based on the biochemical structure, i.e. the main fibril protein involved. The amyloidoses are referred to with 2 capital letters: a capital A (for amyloid) followed by an abbreviation for the fibril protein contained. For example, in a type of amyloidosis called light chain amyloidosis (abbreviated AL), the capital A stands for amyloid, and the capital L stands for the fibril protein which, in this type of amyloidosis, is immunoglobulin light chain or light chain fragment (abbreviated L), hence the abbreviation AL.
Amyloidosis is a relatively rare condition, with the number of new cases per year being about 8 in a million. Patients are usually affected after middle age, and the disease appears to affect all races equally. In developed countries, light chain amyloidosis (AL) is the most common type of systemic amyloidosis, while in developing countries another type called AA amyloidosis is more frequent.