title: Histopathologic Findings in 5 Patients With Hypomyopathic Dermatomyositis: The Importance of MHC-1 Expression on Myofibers.
abstract: Muscle histopathologic findings in hypomyopathic dermatomyositis (HDM) have not been adequately characterized. We sought to determine the results of conventional and immunohistopathology in HDM. Light microscopic and immunohistochemical analysis was performed on muscle from 5 patients with HDM without muscle weakness. Ages ranged from 49 to 56 years. Creatine kinase level was normal. Electromyography showed mild "myopathic" changes in 2. The median duration of skin disease before biopsy was 18 months. Abnormal major histocompatibility (MHC) class I immunoreactivity was noted in myofibers in all specimens even when conventional histopathology was normal (1 patient) or only mildly abnormal (3 patients). One specimen had the characteristic findings of dermatomyositis. Patchy MHC-1 expression on myofibers was a consistent finding in HDM in the absence of other histopathologic abnormalities. The presence of MHC-1 expression could indicate a degree of endoplasmic reticulum stress even in the absence of clinical muscle weakness, muscle enzyme abnormalities, or significant inflammatory infiltrate.
authors.affiliation: *Department of Neurology, Texas Tech University School of Medicine, Lubbock TX; †Division of Rheumatology and Clinical Immunology, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA; ‡Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, PA; and §Department of Pathology (Neuropathology), University of Pittsburgh School of Medicine, Pittsburgh, PA.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: El-Dokla
authors.forename: Rohit
authors.initials: R
authors.lastname: Aggarwal
authors.forename: Chester V
authors.initials: CV
authors.lastname: Oddis
authors.forename: Sara T
authors.initials: ST
authors.lastname: Ali
authors.forename: David
authors.initials: D
authors.lastname: Lacomis
mesh_terms: D001706:Biopsy; D003882:Dermatomyositis / Q000150:complications / Q000473:pathology*; D004568:Electrodiagnosis; D005260:Female; D015395:Histocompatibility Antigens Class I / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D009123:Muscle Hypotonia / Q000150:complications / Q000473:pathology*; D012189:Retrospective Studies
chemical_list: D015395:Histocompatibility Antigens Class I