Profile of various idiopathic inflammatory myopathies at two university hospitals in Yangon, Myanmar

Objective: to determine the distribution of various idiopathic inflammatory center dot myopathies (IIM) and their profile at the largest university hospitals in Yangon, Myanmar. Method: It was a hospital based prospective study recruiting IIM patients admitted to Neurology and Rheumatology ward over a 1.5 year period from September 2017 to February 2019. Results: Among total 51 IIM patients recruited, 62.7% presented to Neurology ward and 373% to Rheumatology ward. Overlap myositis (OM) was the commonest (43%), followed by immune-mediated necrotizing myopathy (IMNM) 27%, dermatomyositis (DM) 24%, polymyositis (PM) 6%. Among OM, anti-synthetase syndrome (ASS) was 23%, and among IMNM, anti-SRP positive was 79%. IMNM and PM patients presented more to neurologists while OM/ASS and DM more to rheumatologists; 82% were females (F:M= 4.6:1). Mean age of onset of myositis was 40.2 +/- 17.8 years, and duration of symptoms before presentation was 10-3,600 days (shortest in anti-SRP and longest in anti-ILMGCR myopathy). Myositis antibodies were positive in 67%. CK range was 40-25,690 U/l, highest in INLNM and lowest in DM. Associated connective tissue diseases among OM in order of descending frequency were 47% systemic lupus erythematosus, 24% Sjogren syndrome, 41% scleroderma and 12% rheumatoid arthritis. Associated cancer identified were one lung cancer in DM, one breast cancer in OM, one buccal cancer in IMNM cases. Conclusions: With recent availability of myositis antibody panel and MHC staining in Myanmar, we have applied current updated classification to describe the first Myanmar data on IIM cases.