OBJECTIVES: To compare the clinical course and muscle biopsy features of polymyositis with mitochondrial pathology (PM-Mito) to inclusion body myositis (IBM) and steroid-responsive inflammatory myopathies (polymyositis). METHODS: We compared clinical, laboratory and myopathologic features in a retrospective study of patients with PM-Mito (23), IBM (26) and polymyositis (12). RESULTS: Selective weakness in the quadriceps or finger flexors was common in PM-Mito (62%) and IBM (87%). Weakness progressed more slowly in PM-Mito than in IBM. PM-Mito patients with more rapidly progressive weakness had more cytochrome oxidase negative muscle fibers. There was no history of benefit from corticosteroid treatment in any PM-Mito or IBM patients. B-cell foci were absent in IBM and PM-Mito. LC3, an autophagy marker, and alphaB-crystallin were common in aggregates in PM-Mito and IBM, but not polymyositis. SMI-31 and TDP-43 positive aggregates were common in IBM but not in PM-Mito or polymyositis. beta-amyloid showed no differences in aggregates among the three groups. CONCLUSIONS: PM-Mito and IBM may be part of the same disease spectrum. PM-Mito has more slowly progressive weakness than IBM and rarely has TDP-43 or SMI-31 staining aggregates in muscle fibers. The most frequent proteins in aggregates in both PM-Mito and IBM are LC3, an autophagy marker, and alphaB-crystallin. Alterations in autophagic degradation pathways may be a common pathogenic mechanism in PM-Mito and IBM. In pathologically typical polymyositis, staining for mitochondrial enzyme activity, aggregates and B-cells helps to distinguish PM-Mito from inflammatory myopathy syndromes that are more likely to respond to corticosteroid treatment.
OBJECTIVES: To compare the clinical course and muscle biopsy features of polymyositis with mitochondrial pathology (PM-Mito) to inclusion body myositis (IBM) and steroid-responsive inflammatory myopathies (polymyositis). METHODS: We compared clinical, laboratory and myopathologic features in a retrospective study of patients with PM-Mito (23), IBM (26) and polymyositis (12). RESULTS: Selective weakness in the quadriceps or finger flexors was common in PM-Mito (62%) and IBM (87%). Weakness progressed more slowly in PM-Mito than in IBM. PM-Mitopatients with more rapidly progressive weakness had more cytochrome oxidase negative muscle fibers. There was no history of benefit from corticosteroid treatment in any PM-Mito or IBM patients. B-cell foci were absent in IBM and PM-Mito. LC3, an autophagy marker, and alphaB-crystallin were common in aggregates in PM-Mito and IBM, but not polymyositis. SMI-31 and TDP-43 positive aggregates were common in IBM but not in PM-Mito or polymyositis. beta-amyloid showed no differences in aggregates among the three groups. CONCLUSIONS: PM-Mito and IBM may be part of the same disease spectrum. PM-Mito has more slowly progressive weakness than IBM and rarely has TDP-43 or SMI-31 staining aggregates in muscle fibers. The most frequent proteins in aggregates in both PM-Mito and IBM are LC3, an autophagy marker, and alphaB-crystallin. Alterations in autophagic degradation pathways may be a common pathogenic mechanism in PM-Mito and IBM. In pathologically typical polymyositis, staining for mitochondrial enzyme activity, aggregates and B-cells helps to distinguish PM-Mito from inflammatory myopathy syndromes that are more likely to respond to corticosteroid treatment.
Authors: Christina A Gurnett; David M Desruisseau; Kevin McCall; Ryan Choi; Zachary I Meyer; Michael Talerico; Sara E Miller; Jeong-Sun Ju; Alan Pestronk; Anne M Connolly; Todd E Druley; Conrad C Weihl; Mathew B Dobbs Journal: Hum Mol Genet Date: 2010-01-02 Impact factor: 6.150
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Authors: Conrad C Weihl; Sara E Miller; Craig M Zaidman; Alan Pestronk; Robert H Baloh; Mohammed Al-Lozi Journal: Neuromuscul Disord Date: 2010-12-04 Impact factor: 4.296
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