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amyloid heart

Etiology: • Unknown. Developments in pathogenesis of various forms and genetic factors are progressing.

Pathogenesis: • AA: Normally, IL-1&6 produced by reactive macrophages stimulate liver to produce SAA. A problem in the degradation of SAA due to its isotype, or other genetic based defects in enzyme function lead to amyloidosis. • AL: Production of immunoglobulins by a clone of plasma cells which are abnormally processed by macrophage enzymes to produce partially degraded light chains which form AL amyloid.

Epidemiology: • These cases are rare. Most common in AL cases, either myeloma related, or "primary", i.e. idiopathic. Heart rarely involved in AA cases. • Rheumatoid arthritis most common disease associated with AA cases. Associated with T.B., leprosy, and osteomyelitis in pre-antibiotic times.

General Gross Description: • Heart may be unremarkable grossly in cases of amyloidosis of aging (>70 yr.). May show stippling of atrial endocardium by 1-2 mm numerous pale deposits. • Heart enlarged in primary (AL) or secondary (AA) amyloidosis with a striking firm stiff consistency, and a uniform myocardial pallor. Gross endocardial and valvular involvement may be see.

General Microscopic Description: • AL and AA:Infiltrations both diffuse interstitial and focal nodular. Interstitial infiltration around each muscle fiber may recall appearence of thick cellulose cell walls around plant cells. Muscle fibers atrophy and become replaced by amyloid. • Endo- and pericardial, valvular and vascular involvement seen. • Amyloid of aging usually shows nodular random lesions and endocardial atrial infiltrates.

Clinical Correlations: • May be asymoptomatic until CHF supervenes with enlarged heart and murmurs. • Arrhythmias common presentation.. • Sudden cardiac death (SCD) seen. • Amyloid heart in aging usually asymptomatic. • Symptoms of ischemic heart disease not usual. • Prognosis poor once symptoms appear.

References: 1. Robbins Pathological Basis of Disease, 5th Edition pp. 231-238, 565. 2. Harrison's Principles of Internal Medicine, 13th Edition, pp. 1625-1630.