Muscle lymphocytic infiltrates in thymoma-associated myasthenia gravis are phenotypically different from those in polymyositis

Zamecnik, Josef; Vesely, Dan; Jakubicka, Branislav; Simkova, Libuse; Pitha, Jiri; Schutzner, Jan; Mazanec, Radim; Vogel, Hannes

doi:10.1016/j.nmd.2007.05.010

« Previous Next »Neuromuscular Disorders
Volume 17, Issue 11 , Pages 935-942, December 2007

Muscle lymphocytic infiltrates in thymoma-associated myasthenia gravis are phenotypically different from those in polymyositis

Josef Zamecnik
- Department of Pathology and Molecular Medicine, Charles University, 2nd Medical Faculty and Faculty Hospital Motol, V Uvalu 84, 150 06 Prague, Czech Republic
- Corresponding author. Tel.: +420 224 435 635; fax: +420 224 435 620.
Dan Vesely
- Department of Pathology and Molecular Medicine, Charles University, 2nd Medical Faculty and Faculty Hospital Motol, V Uvalu 84, 150 06 Prague, Czech Republic
Branislav Jakubicka
- Department of Pathology and Molecular Medicine, Charles University, 2nd Medical Faculty and Faculty Hospital Motol, V Uvalu 84, 150 06 Prague, Czech Republic
Libuse Simkova
- Department of Neurology, Charles University, 1st Medical Faculty, Prague, Czech Republic
Jiri Pitha
- Department of Neurology, Charles University, 3rd Medical Faculty, Prague, Czech Republic
Jan Schutzner
- 3rd Department of Surgery, Charles University, 1st Medical Faculty and Faculty Hospital Motol, Prague, Czech Republic
Radim Mazanec
- Department of Neurology, Charles University, 2nd Medical Faculty, Prague, Czech Republic
Hannes Vogel
- Department of Pathology, Stanford University School of Medicine, Palo Alto, CA, USA

Received 10 April 2007; received in revised form 21 May 2007; accepted 25 May 2007.

Abstract

The aim of the study is to provide evidence that the lymphocytic infiltration of myasthenia gravis (MG) muscle do not represent a true autoimmune myositis, rather an infiltration by naive lymphocytes derived from lymphocyte-rich thymomas. Muscle biopsies from 179 patients with pure MG, 6 thymoma patients without MG and 15 patients with definite polymyositis were analyzed. In 18 patients with MG (all associated with lymphocyte-rich thymomas) and in two thymoma patients without MG, lymphocytic infiltrates were identified in muscles. By use of immunohistochemistry, we demonstrated that the lymphocytes in MG differ from those in polymyositis, being mature but in contrast to polymyositis naive CD45RA+ T lymphocytes. We suggest that the lymphocytic infiltrates in patients with MG and thymoma represent an infiltration of muscle by thymoma-derived mature but naive T cells. The finding of CD8+CD45RA+ lymphocytes in muscle may signify an underlying thymoma and should not be misdiagnosed as polymyositis.

Keywords: Myasthenia gravis, Polymyositis, Thymoma