Lambert-Eaton Syndrome, an Unrecognized Treatable Pediatric Neuromuscular Disorder: Three Patients and Literature Review

BackgroundLambert-Eaton myasthenic syndrome, a presynaptic neuromuscular junction autoimmune disorder, rarely occurs in children. Patients typically present with proximal lower extremity weakness with areflexia.MethodsWe report three children presenting between ages 9 and 10 years diagnosed with Lambert-Eaton myasthenic syndrome 2 years, 1 year, and 5 months later, respectively. Their clinical attributes are correlated with nine other pediatric Lambert-Eaton myasthenic syndrome patients found in our literature review.ResultsThese patients were identified as having Lambert-Eaton myasthenic syndrome during their evaluation for proximal weakness. Low-amplitude compound muscle action potentials classically facilitating >100% with voluntary exercise and/or 50 Hz stimulation were essential to diagnosis. Three of the 12 children had associated malignancies, two of them had lymphoproliferative disorders with onset of symptoms more rapid than the rest, and the third had neuroblastoma. The nine nonparaneoplastic Lambert-Eaton myasthenic syndrome patients responded to immunomodulatory therapy with close return to their baseline function. Complete remission no longer necessitating medication was reported in two patients. Follow-up up to 17 years was available on two patients previously reported.ConclusionLambert-Eaton myasthenic syndrome is a diagnosis that must be considered in children presenting with unidentified proximal muscle weakness. In most children, Lambert-Eaton myasthenic syndrome is a primary autoimmune disorder that is treatable. Nevertheless, a search for malignancy is recommended.