Differences in clinical features between the Lambert-Eaton myasthenic syndrome with and without cancer: an analysis of 227 published cases
Introduction
Lambert-Eaton myasthenic syndrome (LEMS) is a rare antibody-mediated autoimmune disorder [1], [2]. The target antigen, the presynaptic P/Q-type calcium channel, has been studied in great detail. However, the cause of the disease is still elusive. One clue is the association of this disease with small cell lung cancer (SCLC), which is found in over half of the patients [3]. This tumor expresses P/Q-type calcium channels, which suggests that the cause of the disease in these patients is an immunization by their tumor [4]. This explanation is not valid for the other half of the patients with LEMS, who do not have a detectable tumor. A study of 50 LEMS patients showed that patients in whom a cancer was detected had a higher ESR and smoked more frequently than patients without cancer [3]. No other tumor related factors nor any clinical features distinguishing tumor and non-tumor LEMS patients have been found. As LEMS is rare, this might be due to the small number of patients in most studies describing the clinical features of LEMS. We tried to find differences in clinical features by analyzing all published cases of patients with LEMS.
Section snippets
Methods
A literature search in the Medline® database (National Library of Medicine, Bethesda, MD), using the keywords ‘Lambert’, ‘Eaton’, and ‘myasthenic’, was done to collect publications describing individual patients with LEMS. Publications written in English, French, German and Dutch published up to 1999 were taken into account. Papers from the reference list of these publications were screened for description of additional cases. Case descriptions were included when clinical features were
Results
Hundred-and-seventy-eight papers were found describing 270 single cases of LEMS, of which 227 cases in 155 publications fulfilled the criteria for inclusion. Of these cases, 139 patients were men, 88 patients were women (1.6:1). Median age at onset of LEMS was 57 years and ranged between 7 and 80 years. A cancer was detected in 141 patients (62%), who had 24 different types of tumor (Table 1). Time relationship of tumor diagnosis with the onset of symptoms of LEMS was given in 133 cases. Onset
Discussion
This study of 227 patients with LEMS showed significant differences between patients with a tumor and those without one, which so far had not been recognized in smaller groups of patients. Patients with a tumor were more often male, had higher age at onset of LEMS and had a shorter delay between onset of symptoms and diagnosis of LEMS. The frequency of additional immunological disorders was lower in this group. The patients more often had weight loss or need for prolonged artificial ventilation
Acknowledgements
This study was supported by the Princess Beatrix Funds, The Netherlands. A list of the 155 articles from which case reports were included can be obtained from the corresponding author.
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