Amyloidosis is a disease in which abnormal proteins, known as amyloid fibrils, build up in tissue. There are several types with varying symptoms; signs and symptoms may include diarrhea, weight loss, feeling tired, enlargement of the tongue, bleeding, numbness, feeling faint with standing, swelling of the legs, or enlargement of the spleen.There are about 30 different types of amyloidosis, each due to a specific protein misfolding. Some are genetic while others are acquired. They are grouped into localized forms, and systemic ones. The four most common types of systemic amyloidosis are light chain (AL), inflammation (AA), dialysis-related (Aβ2M), and hereditary and old age (ATTR and familial amyloid polyneuropathy).Diagnosis may be suspected when protein is found in the urine, organ enlargement is present, or problems are found with multiple peripheral nerves and it is unclear why. Diagnosis is confirmed by tissue biopsy. Due to the variable presentation, a diagnosis can often take some time to reach.Treatment is geared towards decreasing the amount of the involved protein. This may sometimes be achieved by determining and treating the underlying cause. AL amyloidosis occurs in about 3–13 per million people per year and AA amyloidosis in about 2 per million people per year. The usual age of onset of these two types is 55 to 60 years old. Without treatment, life expectancy is between six months and four years. In the developed world about 1 per 1,000 people die from amyloidosis. Amyloidosis has been described since at least 1639.