Cardiac amyloidosis

Amyloidosis is caused by deposition of products of protein misfolding in extracellular tissue, most commonly the light chains (lambda and kappa), transthyretin, and serum amyloid A. They can be detected by immunofixation tests of serum and urine in most cases. A tissue biopsy like from the bone marrow or endomyocardial biopsy to prove cardiac involvement is the final proof. AL amyloidosis is a plasma cell dyscrasia, which is distinct from multiple myeloma. Transthyretin amyloidosis can be either due to a mutant variety or a wild type. The hall mark of cardiac amyloidosis is thickening of ventricular walls seen on echocardiography without corresponding higher voltages on electrocardiography. In fact they manifest with low voltage in limb leads. Diastolic dysfunction with a restrictive pattern is seen on Doppler studies. Kidney, liver and nerve involvement may be associated features in amyloidosis. AL amyloidosis has a more severe course than transthyretin amyloidosis with median untreated survival of about six months from the onset of cardiac failure. The cardiotoxicity of circulating light chains in addition to the myocardial infiltration is thought to have a role in this more severe manifestation of AL amyloidosis. Capillary fragility due to amyloid infiltration can cause purpuring lesions with minimal trauma. An excellent review on cardiac amyloidosis is available in Circulation. 2011;124:1079-1085.