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Plain Films. Radiographs. PA and Lateral Views. CT Chest. Polymyositis Overlap Syndromes, Anti-Synthetase Syndrome. Epidemiology. DM/PM Syndrome affects mostly adults with a female:male ratio of 3:1
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Epidemiology • DM/PM Syndrome affects mostly adults with a female:male ratio of 3:1 • Relative prevalence exhibits regional latitude in Europe increasing from North (Iceland; RP:0.08) to South (Greece; RP:0.56) (Hengstman, van Venrooij et al. Ann. Rheum. Dis. ; 2000) • Jo-1 antibodies are correlated with HLA-DR3 in Caucasians • Prevalence of antisynthetase antibodies is 20-40% in patients with DM/PM
Pathophysiology • Thought to have precedent viral exposure leading to persistent presence of auto-antigens (molecular mimicry) • UV-B is thought to play a role given prevalence in European countries along latitude. • UV-B stimulates dermal expression of TNF-alpha and other type-1 cytokines • Spectrum includes both humoral mediated (DM) and cell mediated (CD8+ cytotoxic cells in PM) mechanisms • Due to these different mechanisms, both DM, PM, and the overlap syndromes have differing responses to anti-inflammatory agents
Clinical Presentation • Features • Raynaud’s • Proximal muscle weakness vs. combined proximal and distal weakness in inclusion body myositis • Photodermatitis • Mechanic’s hands • Elevated inflammatory markers, variable elevations in CK • Capillary dilation with periungal inflammation • May have amyopathic disease • Subcutaneous calcinosis (anti-synthetase syndrome) • Interstitial Lung Disease (anti-synthetase syndrome) • Symmetric, deforming (but not erosive) polyarthritis (anti-synthetase syndrome)
Physical Exam Findings Adapted from Targoff et al
Physical Exam Findings Adapted from Targoff et al
Physical Exam Findings Adapted from Targoff et al
Autoantibodies • Note that 40% of these DM/PM/Overlap patients have detectable antibodies. Clinical presentation and muscle biopsy then becomes paramount. • + ANA in 80% of cases, don’t discount a negative ANA
ANA Patterns • + ANA, Speckled pattern. DM/PM (anti-Mi2 and SRP antibodies) • + ANA, nucleolar pattern. Overlap of PM with Scleroderma (anti-PM-Scl) • Negative ANA, cytoplasmic pattern. Anti-synthetase syndromes
Anti-Synthetase Syndrome • Anti-Synthetase antibodies • These autoantibodies are directed towards aminoacyl-tRNA synthetases (responsible for transfer of AA to conjugate transfer RNAs) • These are found in the cytoplasm, therefore ANA stains are cytoplasmic and are thus reported as negative (20% of all inflammatory myopathies)
Anti-Synthetase Syndrome • Clinical Manifestation • Patients with antisynthetase syndrome typically present with two or more components of myositis, ILD, and joint involvement • ILD may occur in absence of myositis, particularly associated with PL-12 autoantibodies (Friedman, Targoff, Arnett. Semin Arthritis Rheum; 1996)
Treatment • Physical therapy and an active exercise regimen • Corticosteroids 1mg/kg/day with good success (remission rates of 25-68% achieved) • Non-steroidals (methotrexate .3mg/kg/week, azathioprine 2.5mg/kg/day, cyclophosphamide 3mg/kg/day) used with mild-moderate success • Use IVIG in refractory cases • Case reports describe use of Rituximab in refractory cases
Considerations • In older patients, consider occult malignancy workup • Non-Hodgkin’s Lymphoma associated with DM/PM • May order DEXA scan given prolonged course of corticosteroids • Complications can include steroid induced myopathy (progressive weakness with improved CK) • Most common cause of mortality = complications from ILD leading to pulmonary HTN and hypoxia
References • Hengstman GJD, van Venrooij WJ, Vencovsky J, Moutsopoulos HM, van Engelen BGM. The relative prevalence of dermatomyositis and polymyositis in Europe exhibits a latitudinal gradient. Ann. Rheum. Dis. 59:141-142; 2000. • Plotz PH, Targoff I. Myositis associated antigens. Aminoacyl-tRNA synthetases. In : Manual of Biological Markers of Disease. Eds,WJ Van venrooij and R Maini. Kluwer Academic Publications. The Netherlands. pp B6.1: 1-18; 1994. • Love LA, Leff RL, Fraser DD, Targoff IN, Dalakas M, Plotz PH, Miller FW. A new approach to the classification of idiopathic inflammatory myopathy: myositis-specific autoantibodies define useful homogeneous patient groups. Medicine (Baltimore) 70:360-74; 1991. • Friedman AW, Targoff IN, Arnett FC. Interstitial lung disease with autoantibodies against aminoacyl-tRNA synthetases in the absence of clinically apparent myositis. Semin Arthritis Rheum 26:459-67; 1996. • Grathwohl KW, Thompson JW, Riordan KK, Roth BJ, Dillard TA. Digital clubbing associated with polymyositis and interstitial lung disease. Chest 108:1751-2; 1995. • Kalenian M, Zweiman B Inflammatory myopathy, bronchiolitis obliterans/organizing pneumonia, and anti-Jo-1 antibodies: an interesting association. Clin Diagn Lab Immunol 4:236-40;1997. • Targoff IN, Arnett FC Clinical manifestations in patients with antibody to PL-12 antigen (alanyl-tRNA synthetase). Am J Med 88:241-51; 1990. • Lee W, Zimmermann B 3rd, Lally EV.Relapse of polymyositis after prolonged remission. J.Rheumatol 24:1641-4; 1997. • Dalakas MC. Current treatment of the inflammatory myopathies. Curr Opin Rheumatol 6:595-601; 1994.