A Unique Case of Non-paraneoplastic Lambert-Eaton Myasthenic Syndrome Treated with Subcutaneous Immunoglobulin
Sojung Park1, Melanie Taylor2
1Neurology, Trinity Health Grand Rapids, 2Neurology, Trinity Health Grand Rapids
Objective:
To report a case of non-paraneoplastic Lambert-Eaton myasthenic syndrome treated successfully with subcutaneous immunoglobulin
Background:
Lambert-Eaton myasthenic syndrome (LEMS) is a neuromuscular autoimmune disease caused by pathogenic autoantibodies directed against voltage-gated calcium channels present on the presynaptic nerve terminal. For LEMS patients refractory to initial symptomatic treatment with amifampridine, immunomodulatory therapy with intravenous immunoglobulin (IVIG) is often utilized. In the authors’ review of literature, the utility of subcutaneous immunoglobulin in the treatment of LEMS has been scarcely reported.
Design/Methods:
Case report
Results:
A 27-year-old female with a history of postpartum depression presented with a four-year history of weakness in proximal lower extremities, previously misdiagnosed as fibromyalgia. Workup revealed positive P/Q-type voltage-gated calcium channel antibodies in serum and was negative for underlying malignancy. Electromyography (EMG) showed post-exercise compound motor action potential facilitation, supporting the diagnosis of Lambert-Eaton myasthenic syndrome (LEMS). There were 233.3% and 1150.0% increases from pre- to post-exercise amplitudes in median and ulnar nerves, respectively. She was started on amifampridine and eventually intravenous immunoglobulin (IVIG), which she did not tolerate due to myalgia and intolerable headaches. Subsequently, subcutaneous immunoglobulin (SCIG) was tried, which was well tolerated and resulted in excellent clinical response. Repeat EMG after one year of being treated with SCIG showed an improvement compared to the initial study, with 103.8% and 520.0% increases from pre- to post-exercise amplitudes in median and ulnar nerves, respectively.
Conclusions:
The diagnosis of non-paraneoplastic LEMS requires a high level of clinical suspicion, and prompt diagnosis is necessary to facilitate treatment. Subcutaneous immunoglobulin therapy may be a reasonable alternative for patients with LEMS who do not tolerate the intravenous formulation.