J Clin Neurol.  2012 Dec;8(4):305-307. 10.3988/jcn.2012.8.4.305.

A Case of Lambert-Eaton Myasthenic Syndrome with Small-Cell Lung Cancer and Transient Increase in Anti-Acetylcholine-Receptor-Binding Antibody Titer

• Lee JH
• Shin HY
• Kim SM
• Sunwoo IN

• KMID: 2287583
• DOI: http://doi.org/10.3988/jcn.2012.8.4.305

Abstract

BACKGROUND
Lambert-Eaton myasthenic syndrome (LEMS) is a presynaptic neuromuscular junction disorder that is most frequently associated with small-cell lung cancer (SCLC). The titers of antibodies against voltage-gated calcium channels are frequently increased in LEMS, but only rarely is titer of anti-acetylcholine-receptor-binding antibodies (AChR-abs) increased.
CASE REPORT
A 57-year-old male was admitted to our hospital due to dry mouth and eyes and progressive proximal limb weakness of 2 months duration. The results of a repetitive nerve stimulation test disclosed all criteria for the electrophysiological LEMS pattern, and the patient's AChR-abs titer was 0.587 nmol/L. At a follow-up performed 5 years after successful treatment of SCLC and LEMS, his AChR-abs titer had decreased to 0.001 nmol/L.
CONCLUSIONS
We suggest that this was a case of transient pseudopositivity of AChR-abs in SCLC with LEMS.

Keyword

Lambert-Eaton myasthenic syndrome; small-cell lung carcinoma; myasthenia gravis

MeSH Terms

Antibodies
Calcium Channels
Extremities
Eye
Follow-Up Studies
Humans
Lambert-Eaton Myasthenic Syndrome
Lung
Lung Neoplasms
Male
Mouth
Myasthenia Gravis
Neuromuscular Junction Diseases
Antibodies
Calcium Channels

Figure

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  Fig. 1 Repetitive nerve stimulation test (RNST; A and C) and serial chest computed tomography (CT; B and D) and results before (A and B) and after (C and D) cancer treatment. The initial RNST (A) revealed electrophysiological patterns typical of Lambert-Eaton myasthenic syndrome: low compound muscle action potentials (1133.7 V; upper-left panel), postexercise facilitation (+121.1%; lower-left panel), a decrement (-65.7%) on low-frequency repetitive stimulation (3 Hz; upper-right panel), and an increment (+916%) on high-frequency repetitive stimulation (50 Hz; lower right panel) for the abductor digiti quinti. The initial chest CT (B) revealed a mass of approximately 1.6 cm in the anterior segment of the right lower lobe (white arrow). On follow-up studies at 13 months after treatment, the RNST responses had normalized (C) and the lung mass had completely disappeared on chest CT (D).

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