Tel Hashomer camptodactyly syndrome (THCS) was diagnosed in a 4-month-old boy whom we have followed for 12 years. In addition to the characteristic clinical findings, he had preductal coarctation of the aorta, persistent ductus arteriosus, and multiple ventricular septal defects. The electron-microscopic evaluation of his muscle biopsy showed anomalies of the sarcoplasmic reticulum and mitochondria; the organization of the myofibrils was normal. The morphological findings suggested primary or secondary involvement of neuromuscular signal transduction and involvement of mitochondria in the development of the myopathy in this child.