The prevalence, epidemiological characteristics and mortality trends of inflammatory myopathies patients in Oman: the Prevision study.

Objectives: This research aims to investigate the prevalence, epidemiological characteristics, mortality rates, survival rates and the rate of malignancy in patients diagnosed with inflammatory myopathies (IIM) in Oman.

Methods: This is a longitudinal study, that covered a span of 16 years at eight rheumatology centres in Oman. The study included all adults and paediatric patients diagnosed with different types of idiopathic inflammatory myopathies (IIM) and who fulfil either the Bohan classification criteria or the 2017 EULAR/ACR classification criteria.

Results: The study included a total of 116 patient with an average age of 38.78 (±17.61 SD) years. The most prevalent form of myositis was found to be dermatomyositis (DM) 48 (41.38%), followed by polymyositis (PM) 36 (31.03%) and juvenile myositis (JDM) 18(15.52%). However, inclusion body myositis and necrotising myopathy were relatively rare conditions. The prevalence rates for DM, PM and JDM were determined as 2.2, 2.2, and 1.14 per 100,000 population respectively. Cardiac complications were observed in 14.66% of cases. Among the individuals studied, a history of malignancy was present in around 1.72% of cases. ANA antibodies were present in 71.55% of the cases, anti-Jo 1 and anti-RNP/SM antibodies were detected in 8.62%, and Anti-Ro antibodies in 24.14%. The overall mortality rate was found to be 6.90% with a rate of 11.1% among JDM cases. The five-year survival rates for PM, DM and JDM were found to be 94.4%, 91.7% and 89.0% respectively. These rates decline over a 10-year period to 67%, 69% and 83.3% respectively.

Conclusions: The study highlights the prevalence, mortality, and survival rates of IIM in Oman. Patients with JDM had a higher mortality rate. This underscores the significance of using novel healthcare strategies to improve clinical outcomes and meet special requirements for this group of patients.