Classification of amyloidosis
Amyloidosis is classified according to the type of accumulated protein and according to the underlying disease. These are all relatievly rare illnesses, but some occur more frequently than others, and these are briefly described below.
AL amyloidosis stands for Amyloid Light Chain Amyloidosis. The accumulating proteins are small proteins, known as light chains, and can be one of two types: either kappa or lambda. They are created by a type of white blood cells, called plasma cells in the bone marrow. Everyone has plasma cells, in their bone marrow, that create kappa and lambda protein. Plasma cells are important to our immune system, as they create the natural antibodies that protect us against infections. In patients with AL amyloidosis, dysplasia takes place, which leads to formation of a changed protein with an abnormal composition and form. This means that the proteins have a tendency to accumulate. The underlying problem is the dysplasia of the plasma cells, and this type of amyloidosis can be treated with a type of chemotherapy, which destroys the transformed plasma cells. The dysplasia is not malignant, and AL amyloidosis is not a cancer, but the illness is serious due to the accumulation.
ATTR amyloidosis stands for Amyloid Transthyretin Amyloidosis. Transthyretin is a bigger protein than the light chains. We all create transthyretin, which is the originator of the most dominant protein we have in our serum, i.e. albumin. Transthyretin is also known as prealbumin. There are two types of transthyretin amyloidosis: a hereditary type and an acquired age-related type. The hereditary type is caused by an abnormality in the gene that codes the formation of transthyretin. The transthyretin protein, which is formed, therefore has a slightly different structure than normally, and it is this difference that is significant enough that the protein has a tendency to cause accumulation. There are two main types of the hereditary type; one that most frequently attacks the nerve pathways and leads to chronic nerve stress , and another type, which most frequently affects the heart and causes enlargement of the heart as well as heart failure. Even though this type of amyloidosis is inherent, symptoms occur relatively late in adulthood, e.g. at 40-60 years of age. The non-hereditary type of ATTR amyloidosis is typically seen in older patients and is therefore named “Senile amyloidosis”. It typically also affects the heart.
AA amyloidosis stands for Apoprotein A amyloidosis and is also known as secondary amyloidosis. Occurs in patients with long-term chronic infections, chronic inflammations and chronic, active rheumatism. This type is more frequent in developing countries, but has become rarer in Denmark, as treatment of infections and rheumatism has improved significantly. In connection with AA amyloidosis, it is important to ensure that the underlying triggering illness is treated as well as possible.
Beta 2 microglobulin amyloidosis is caused by accumulation of the protein, Beta 2 microglobulin. This type is typically seen in patients with chronic kidney disease and is caused by the amount of Beta 2 microglobulin in the blood increasing in connection with kidney failure.