An 8-year-old black girl with a 5 month history of systemic lupus erythematosus (SLE) and secondary antiphospholipid syndrome (APS) developed Raynaud's phenomenon, marked hemolytic anemia, and a fatal myocardial infarction (MI). Pathologic evaluation of the heart demonstrated a transmural acute MI associated with a recent thrombus of the circumflex coronary artery, thrombosis of small intramural arteries, and a coronary arteriopathy resembling fibromuscular dysplasia. Inflammatory or atherosclerotic changes of the coronary arteries were distinctly absent. This case represents the youngest reported patient with SLE, MI, and pathologic confirmation of nonatheromatous coronary artery disease. The observed coronary pathological findings may have accentuated the thrombogenic potential of the APS, resulting in coronary thrombosis. Cardiac lesions in SLE and APS are reviewed, and pathogenetic considerations for the coronary vasculopathy are discussed.