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Type 2 fiber predominance in Lambert-Eaton myasthenic syndrome
M Squier1, C Chalk, D Hilton-Jones
1Department of Neuropathology, University of Oxford, Radcliffe Infirmary, United Kingdom.
Abstract:
Serial muscle biopsies in a noncarcinomatous case of Lambert-Eaton myasthenic syndrome (LEMS) have shown progressive atrophy and loss of type 1 fibers, resulting in overwhelming type 2 predominance. A similar abnormality was found in a single biopsy from a second case of LEMS without associated carcinoma. Review of the literature suggests that type 2 fiber predominance has been observed in at least one other biopsied case. Interference with transmitter release caused by anti-voltage-gated calcium channel antibodies may deprive type 1 muscle fibers of the low frequency discharge necessary to maintain their metabolic properties.