Byline: Bahig M. Shehata (1), Kathleen Patterson (2), Jean E. Thomas (3), Diane Scala-Barnett (4), Sarada Dasu (5), Haynes B. Robinson (6) Keywords: Key words: cardiomyopathy, histiocytoid, arrhythmia, SIDS, X-linked Abstract: Histiocytoid cardiomyopathy (HC), a rare arrhythmogenic disorder, presents as difficult-to-control arrhythmias or sudden death in infants and children, particularly girls. Three cases are described with autopsy findings. In two cases, yellow-tan nodules were grossly visible in the myocardium in the third case, no gross lesions were identified. Microscopic examination in all three cases revealed multiple, scattered clusters of histiocytoid myocytes which on ultrastructural examination were filled with abnormal mitochondria, scattered lipid droplets, and scanty myofibrils. These pathologic findings are similar to those previously described. The pathogenesis of this entity remains controversial. It was recently proposed that this disorder is X-linked dominant with the associated gene located in the region of Xp22. Author Affiliation: (1) Department of Pathology, Children's Medical Center of Northwest Ohio, 2142 North Cove Boulevard, Toledo, OH 43606, USA , US (2) Department of Pathology, Children's Hospital and Medical Center, 4800 Sandpoint Way NE, Seattle, WA 98105, USA , US (3) Medical College of Ohio, 3000 Arlington Avenue, P.O. Box 10008, Toledo, OH 43699, USA , US (4) Office of the Coroner of Lucas County, 2595 Arlington Avenue, Toledo, OH 43614, USA , US (5) Department of Pathology, Children's Hospital Medical Center of Akron, 281 Locust, Akron, OH 44308, USA , US (6) Fetal Developmental Evaluations, 3144 W Central Avenue, P.O. Box 2847, Toledo, OH 43606, USA , US Article note: Received October 7, 1996 accepted April 17, 1997