Amyloidosis
| Amyloidosis | |
|---|---|
 |
|
| Classic facial features of AL amyloidosis with purpura around the eyes | |
| Classification and external resources | |
| Specialty | endocrinology, rheumatology, cardiology |
| ICD-10 | E85 |
| ICD-9-CM | 277.3 |
| DiseasesDB | 633 |
| eMedicine | med/3377 |
| Patient UK | Amyloidosis |
| MeSH | D000686 |
Amyloidosis is a rare and serious disease caused by accumulation of proteins in the form of abnormal, insoluble fibres, known as amyloid fibrils, within the extracellular space in the tissues of the body. Amyloid deposits can be confined to only one part of the body or a single organ system in 'local amyloidosis' or they can be widely distributed in organs and tissues throughout the body in 'systemic amyloidosis'. The symptoms of amyloidosis are accordingly highly variable and confirmation of the presence of amyloid in the tissues can be challenging, so that diagnosis is often delayed.
Amyloid fibrils are formed by aggregation (clumping) of normally soluble body proteins and accumulate progressively, forming amyloid deposits which disrupt the normal tissue architecture, damaging the function of tissues and organs and causing disease. In contrast to the normally efficient clearance of abnormal debris from the tissues, amyloid deposits are removed very slowly, if at all. There are many different types of amyloidosis, each caused by formation of amyloid fibrils from different soluble precursor proteins in different patients. About 30 different proteins are known to form amyloid fibrils in humans and amyloidosis is named and classified according to the identity of the respective fibril protein.
The presentation of amyloidosis is broad and depends on the site of amyloid accumulation. The kidney and heart are the most common organs involved.
Amyloid deposition in the kidneys can cause nephrotic syndrome, which results from a reduction in the kidney's ability to filter and hold on to proteins. The nephrotic syndrome occurs with or without elevations in creatinine and blood urea concentration, two biochemical markers of kidney injury. In AA amyloidosis the kidneys are involved in 91–96% of people, symptoms ranging from protein in the urine to nephrotic syndrome and rarely renal insufficiency.
Amyloid deposition in the heart can cause both diastolic and systolic heart failure. EKG changes may be present, showing low voltage and conduction abnormalities like atrioventricular block or sinus node dysfunction. On echocardiography the heart shows a restrictive filling pattern, with normal to mildly reduced systolic function. AA amyloidosis usually spares the heart.
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