GIANT-CELL MYOCARDITIS - AN ENTITY DISTINCT FROM SARCOIDOSIS CHARACTERIZED BY MULTIPHASIC MYOCYTE DESTRUCTION BY CYTOTOXIC T-CELLS AND HISTIOCYTIC GIANT-CELLS

Giant cell myocarditis (GCM) is a rare, rapidly fatal myocarditis with histologic features that have some similarities to cardiac sarcoidosi s (CS). The natures of the inflammatory infiltrates of GCM and CS have not been systematically compared. We retrospectively compared the imm unohistochemical and light microscopic findings at autopsy in eight he arts with GCM and seven hearts with CS. The patients with GCM were six women and two men (mean age, 50 +/- 13 yr) who presented with congest ive heart failure with a mean duration of 46 days until death (range, 1-180 d). We observed three histologic phases, often within a single h eart. The acute phase (seven cases of eight) demonstrated an extensive infiltrate of lymphocytes and eosinophils with plentiful macrophages and macrophage-derived KP-1 positive giant cells (GCs) associated with myocytic necrosis. No granulomas were identified. A healing phase (th ree cases of eight) showed granulation tissue, moderate macrophagic GC s, and scattered KP-1-negative myogenic GCs. A healed phase (three cas es of eight) showed dense scar with no GCs. Macrophagic GCs were prese nt preferentially in areas of myocytic damage and were never present i n epicardial fat The majority of lymphocytes were T cells, with a pred ominance of CD8 cells, The seven patients with CS were men (mean age, 44 +/- 18 yr). Six patients presented with sudden cardiac death and on e with congestive heart failure. The histologic patterns were similar in all seven, with scattered interstitial and epicardial (five cases o f seven) granulomas composed of KP-1 positive macrophages and macropha gic GCs and T lymphocytes, which were predominantly CD4 cells. Necrosi s, myogenic GCs, and significant numbers of eosinophils were absent. D ense scarring was present in five cases of seven GCM is characterized by myocytic destruction mediated by cytotoxic T cells, macrophagic GCs , and eosinophils. In contrast, CS is an interstitial granulomatous di sease without myocytic necrosis.