Introduction: Lambert-Eaton myasthenic syndrome (LEMS) is a rare autoimmune disorder affecting the neuromuscular junction, clinically characterized by proximal muscle weakness and autonomic changes. LEMS is often associated with an underlying tumor (paraneoplastic form) but also occurs in the absence of cancer (idiopathic form). Treatment consists of immunomodulation (immunosuppression), anticancer treatment when carcinoma is present, and symptomatic treatment [acetylcholinesterase inhibitors and potassium channel blockers, e.g., amifampridine (3,4-diaminopyridine, i.e., 3,4-DAP), to improve neurotransmission]. Although there has long been information from case reports, several randomized controlled trials, and treatment guidelines, population data are still scarce.
Methods: The LEMS patient registry was launched in the European community in mid-2010 as a voluntary, multinational, observational, non-interventional program to collect structured empirical data on clinical course, treatment utilization, and safety and efficacy from the use of LEMS-specific treatments.
Results: Sixty-nine patients have been enrolled [36 males, 32 females, 1 gender not reported; mean age 61.5 (27-84) years]. Eighteen patients (26%) were diagnosed with an associated carcinoma. At the time of enrollment, the majority of patients (65%) were receiving amifampridine [either compounded 3,4-DAP (22%) or 3,4-DAP phosphate, Firdapse(®) (43%)]. At enrollment, most patients demonstrate a profile of mild-to-moderate deficits in daily functioning but generally have good muscle strength, albeit with reduced deep tendon reflexes, frequent ataxia during walking, and signs of autonomic dysfunction including dry mouth, bladder dysfunction, and constipation.
Conclusion: The LEMS European Union registry will continue to enroll patients and periodically report the accrued longitudinal data obtained on clinical assessments and laboratory findings, treatment practices, the safety and efficacy of treatment approaches, and long-term clinical outcomes.
Funding: BioMarin Pharmaceutical Inc., Novato, CA, USA.
Keywords: 3,4-Diaminopyridine (3,4-DAP); Amifampridine; Firdapse; LEMS; Lambert–Eaton; Registry.