Richard J. Lederman, M.D., Ph.D.
Ronald M. Bukowski, M.D.
Paul Nickerson, M.D.
Myopathy with malignant carcinoid syndrome appears to be rare. A 52-year-old woman with a 9-year history of carcinoid symptoms and biopsy-proven metastatic carcinoid of the liver is reported. After 6 months of chemotherapy, proximal weakness and atrophy with electromyographic and histological evidence of myopathy developed. Urinary 5-HIAA and plasma serotonin levels were markedly elevated. Charts of 44 patients with malignant carcinoid tumors were reviewed; six of these had symptoms of neuromuscular disease but only one had objective weakness. Five of six had moderate to marked elevation of blood serotonin; the sixth had no assay. Only one other patient had high serotonin levels but had no weakness. The findings support a pathogenetic role for circulating serotonin in this unusual myopathy, although the mechanism remains uncertain.