IngentaConnect Clinical and experimental features of MuSK antibody positive MG i...

Authors: Ohta, K.¹; Shigemoto, K.²; Fujinami, A.³; Maruyama, N.⁴; Konishi, T.⁵; Ohta, M.

Source: European Journal of Neurology, Volume 14, Number 9, September 2007 , pp. 1029-1034(6)

Abstract:

We investigated the presence of antibodies (Abs) against muscle-specific tyrosine kinase (MuSK) in Japanese myasthenia gravis (MG) patients. MuSK Abs were found in 23 (27%) of 85 generalized seronegative MG (SNMG) patients but not in any of the ocular MG patients. MuSK Ab-positive patients were characterized as having female dominance (M:F, 5:18), age range at onset 18 to 72 (median 45) years old, and prominent oculobulbar symptoms (100%) with neck (57%) or respiratory (35%) muscle weakness. Limb muscle weakness was comparatively less severe (52%), thymoma absent. Most patients had good responses to simple plasma exchange and steroid therapy. MuSK IgG from all 18 patients was exclusively the IgG 4 subclass and bound mainly with the MuSK Ig 1-2 domain. Serial studies of 12 individuals showed a close correlation between the variation in MuSK Ab titers and MG clinical severity (P = 0.01 by Kruskal-Wallis). MuSK Ab titers were sharply decreased in patients who had a good response to early steroid therapy or simple plasma exchange, but there was no change, or a rapid increase on exacerbation after thymectomy. Measurement of MuSK Ab titers aids in the diagnosis of MG and the monitoring of clinical courses after treatment.

Keywords: clinical features; domain; IgG subclass; muscle specific tyrosine kinase; MuSK antibody; myasthenia gravis; seronegative myasthenia gravis

Document Type: Research article

DOI: 10.1111/j.1468-1331.2007.01870.x

Affiliations: 1: Clinical Research Center, Utano National Hospital, Kyoto, Japan 2: Department of Preventive Medicine, Faculty of Medicine, Graduate School of Ehime University, Ehime, Japan 3: Department of Medical Biochemistry, Kobe Pharmaceutical University, Kobe, Japan 4: Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan 5: Department of Neurology, Utano National Hospital, Kyoto, Japan

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Clinical and experimental features of MuSK antibody positive MG in Japan