Investigators from Boston Children's Hospital; the Lahey Clinic, Burlington, MA; and Ohio State University, report 3 children presenting between ages 9 and 10 years with proximal lower extremity weakness with areflexia and low-amplitude compound muscle action potentials, and diagnosed with Lambert-Eaton myasthenic syndrome. A literature review found 9 other pediatric cases of Lambert-Eaton myasthenic syndrome, 3 having associated malignancies, 2 with lymphoproliferative disorders and 1 with neuroblastoma. The 9 nonparaneoplastic patients with primary autoimmune disorder responded to immunomodulatory therapy, with complete remission in 2 patients. [1]

COMMENTARY. Diagnosis of Lambert-Eaton myasthenic syndrome. Usually diagnosed as a paraneoplastic disease affecting middle-aged adults with small-cell lung cancer, Lambert-Eaton myasthenic syndrome (LEMS) may occur as a primary autoimmune disorder in younger adults and rarely in children. Proximal muscle weakness, absent reflexes, normal serum creatine kinase, and autonomic dysfunction should prompt electrodiagnostic testing for LEMS. Low-amplitude compound muscle action potentials with >100% facilitation following 10 seconds of voluntary exercise or in response to high frequency repetitive motor nerve stimulation (when tolerated) is diagnostic. Serum titers of voltage-gated calcium channel receptor antibodies specific to LEMS will differentiate the disorder from myasthenia gravis [1, 2]. Identification of LEMS will prompt a search for malignancy.