MG and LEMS overlap syndrome: case report with electrophysiological and immunological evidence

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Abstract

Objective: To report the clinical, electrophysiological, and immunological findings in one patient with MG and LEMS overlap syndrome (myasthenia gravis and Lambert-Eaton myasthenic syndrome).

Methods: Evaluation of clinical, electrophysiological, and immunological findings in one patient with this disease.

Results: A female patient with pernicious anemia had clinical findings of ptosis, diplopia, proximal leg weakness, areflexia and a positive edrophonium test as well as the classic patterns initially of MG and later of LEMS on successive repetitive nerve stimulation (RNS) tests. Immunologically she demonstrated positive acetylcholine receptor antibody (ACh-ab) and positive N-type voltage-gated calcium-channel antibody (VGCC-ab) titers.

Conclusions: Among five reported cases combining the features of MG and LEMS and having positive AChR- and VGCC-ab titers, our patient provides the most convincing clinical, electrophysiological, and immunological evidence for the existence of MG and LEMS overlap syndrome.

Significance: MG and LEMS overlap syndrome is a distinct entity.

Introduction

Several cases showing the combined features of myasthenia gravis (MG) and Lambert-Eaton myasthenic syndrome (LEMS) have been reported (Matsumoto et al., 1999, Oh et al., 1987). These cases were characterized by the following: (1) common oculo-bulbar symptoms, (2) a good response to edrophonium, (3) areflexia, (4) the ‘LEMS triad’ in the repetitive nerve stimulation (RNS) test, and (5) absence of small-cell lung cancer (SCLC). However, the actual existence of an MG and LEMS overlap syndrome has been questioned. In 1987, we reported one case of combined MG and LEMS (Oh et al., 1987). This is a follow-up report of the same case, describing the new finding of positive voltage-gated calcium-channel antibody (VGCC-ab), the persistent LEMS pattern in the subsequent RNS tests, and additional SFEMG and acetylcholine receptor antibody (AChR-ab) findings.

Section snippets

Clinical features

A 26-year-old woman with pernicious anemia presented with ptosis, diplopia, proximal leg weakness, a positive edrophonium test, the classic MG pattern in the RNS test (normal CMAP amplitude and decremental response at the low rate of stimulation [LRS]), and a positive AChR-ab titer at the initial evaluations in July and September 1980 (Table 1). A thymectomy was performed. When symptoms returned 6 months after a brief remission, the patient had diplopia, ptosis, hip flexor weakness, and

Discussion

At the initial evaluation our patient demonstrated all the clinical, electrophysiological, and immunological criteria of MG. The only atypical finding was areflexia, which was thought to be due to pernicious anemia. Later studies showed that this patient had the clinical, electrophysiological, and immunological criteria of LEMS. Atypical features for LEMS were oculo-bulbar palsy, a good response to edrophonium and frequent low positive AChR-ab titers.

Twenty one cases showing combined MG and

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