Prostate carcinoma and the Lambert-Eaton myasthenic syndrome.

Abstract

In 1957 Eaton and Lambert described a paraneoplastic myasthenic syndrome, which is most frequently associated with small cell carcinoma of the lung. This syndrome typically presents with weakness and fatigability of proximal limb muscles and hyporeflexia without ocular or bulbar disturbance. The syndrome is an autoimmune disease characterized by autoantibodies against voltage-gated calcium channels leading to paucity of acetylcholine release at presynaptic membranes. In small cell carcinomas of the lung expression of voltage-gated calcium channels provides an antigenic stimulus for production of antibodies that cross-react with calcium channels in the central and autonomic nervous systems. Nerve conduction studies are required for confirmation of the Lambert-Eaton myasthenic syndrome with postexercise facilitation greater than 100% of the compound muscle action potential being diagnostic. While the Lambert-Eaton myasthenic syndrome is recognized in 3% of cases of pulmonary small cell carcinoma, the incidence is unknown for other types of malignancy. We report a case of neuroendocrine carcinoma of the prostate arising in adenocarcinoma in which disease progression was marked by development of the Lambert-Eaton myasthenic syndrome.