This study was performed in order to characterize the types of the infiltrating cells, and the expression profiles of major histocompatibility complex (MHC) class I and membrane attack complex (MAC) in patients with inflammatory myopathies and dysferlinopathy. Immunohistochemical stains were performed using monoclonal antibodies against several inflammatory cell types, MHC class I, and MAC in muscles from inflammatory myopathies and dysferlinopathy. There was significant difference in the types of infiltrating cells between polymyositis (PM), dermatomyositis (DM), and dysferlinopathy, including significantly high CD4+/CD8+ T cell ratio and B/T cell ratio in DM. In dysferlinopathy, CD4+ T cells were the most abundant and the proportions of infiltrating cell types were similar to those of DM. MHC class I was expressed in muscle fibers of PM and DM regardless of the presence of inflammatory infiltrates. MAC was expressed in necrotic fibers and vessels of PM and DM. One patient with early stage DM had a MAC deposits on endomysial capillaries. In dysferlinopathy, MAC deposit was also observed on the sarcolemma of nonnecrotic fibers. The analysis of inflammatory cells, MHC class I expressions and MAC deposits may help to differentiate dysferlinopathy from idiopathic inflammatory myopathy.
Adult ; Aged ; *Dermatomyositis/immunology/pathology ; Female ; Genes, MHC Class I ; Humans ; Male ; *Membrane Proteins/genetics/immunology ; Middle Aged ; Muscle Fibers, Skeletal/cytology/immunology/pathology ; *Muscle Proteins/genetics/immunology ; *Muscular Dystrophies, Limb-Girdle/immunology/pathology ; *Myositis/immunology/pathology ; *Polymyositis/immunology/pathology ; T-Lymphocytes/cytology/immunology/pathology ; Young Adult

INTRODUCTIONDermatomyositis (DM) is a multisystem inflammatory disease with a strong association with malignancy. We aimed to describe a series of Asian patients with DM and identify any significant clinical factors associated with malignancy.

MATERIALS AND METHODSThis was a retrospective review of a multi-racial cohort of 69 Asian patients diagnosed with DM over an 11-year period from 1996 to 2006.

RESULTSMalignancy was detected in 15 out of 68 patients (22%), the most common of which was nasopharyngeal carcinoma (7 cases). Compared to the non-malignancy group, the malignancy-associated group was older and had more male patients. There were no statistically significant clinical, serological or laboratory factors associated with a higher risk of malignancy.

CONCLUSIONThis study highlights the importance of ongoing malignancy screening especially for nasopharyngeal carcinoma in Asian patients with DM.

Adolescent ; Adult ; Aged ; Aged, 80 and over ; Carcinoma ; Confidence Intervals ; Dermatomyositis ; complications ; epidemiology ; immunology ; pathology ; Female ; Humans ; Logistic Models ; Male ; Middle Aged ; Muscle Weakness ; Nasopharyngeal Neoplasms ; epidemiology ; immunology ; pathology ; Odds Ratio ; Paraneoplastic Syndromes ; complications ; epidemiology ; immunology ; pathology ; Retrospective Studies ; Risk Factors ; Singapore ; epidemiology ; Young Adult