Sree Chitra Tirunal Institute for Medical sciences and Technology ...

IBM PM DMAge at onset >50 adults All agesSex M F FFamily history Rare No NoAss.with No slight yesmalignancyConnective tissue 15% yes yesdisorderWeakness P=D P>D P>DRash No No YesCPK 10 50 times 50 timesResponse to Rx poor variable GoodBiopsy Rimmed vacuoles EM inflammation PV inflammation'Amyloid deposits Muscle fiber invasion Complement depositsTubulofilaments CD8+ T cells .CD4+ and B cellsTable II: Comparison of major types of inflammatory muscle diseaseTen important points to ponder1. Pain and discomfort are rarely prominent in myositis2. The normal upper limit for serum creatine kinase is higher than we usually think3. Failure io appreciate points 1 and 2 leads to many patients being wronglydiagnosed, and treated, as having polymyositis4. Pure polymyositis is a rare condition5. Inflammatory infiltrates in a muscle biopsy may be a secondary phenomenon andfailure to appreciate this is a common reason for wrong diagnosis andinappropriate treatment6. Absence of inflammatory infiltrates in a biopsy does not exclude myositis7. Despite their clinical similarities, dermatomyositis and polymyositis arefundamentally different disorders in terms of pathogenesis8. Inclusion body myositis, the most common acquired myopathy over the age of 50years, is frequently misdiagnosed as polymyositis. Whether it is a true "myositis"remains hotly debated ,9. Dermatomyositis may be a paraneoplastic disorder, particularly in the elderly10. Long term morbidity and mortality relate to interstitial lung disease, myocardialinvolvement, and associated malignancy19