Idiopathic inflammatory myopathies - The burden of disease: Cohort analysis focusing on damage and comorbidities

Introduction/Background: Idiopathic Inflammatory Myopathies (IIM) continue to be a major clinical challenge worldwide. The exact aetiopathogenesis of this chronic and disabling disease remains elusive, preventing the development of novel and effective therapeutic strategies and leading to a high incidence of damage. The complexity of treating these diseases is even greater due to the numerous comorbidities that affect these patients. Methods: Retrospective review of the cohort of patients diagnosed with IIM and followed in a dedicated unit of a tertiary hospital between 1971 and December 2022, with particular attention to damage and comorbidities. Damage was assessed using the Myositis Damage Index. Comorbidities were recorded and analysed as a whole and also assessed using the Charlson Comorbidity Index. Health Assessment Questionnaire (HAQ) Disability Index (DI) was performed by phone call in December 2022, to all patients actively followed-up in the Unit.Results: Analysis of 149 patients with a mean follow-up of 9 years (range 0-51) revealed >90% with damage and comorbidities. Most comorbidities were a consequence of the damage and were particularly related to prolonged steroid therapy. Cardiovascular damage, which occurred either as cardiovascular risk factors or as end-organ sequelae (cardiovascular disease and chronic kidney disease), was the main cause and a major contributor to death. Depression was also high on the list of associated comorbidities. Median HAQ was 2.09 representing high negative impact in quality of life.Conclusions: Although survival rates have increased in recent decades, patients with IIM carry a high burden of disease with poor quality of life, mainly caused by damage and comorbidities.While comorbidities accumulation is the major factor for poor quality of life, damage severity is the main predictor for mortality. Improved therapeutic strategies are needed to reduce the need for steroids and to introduce routine screening and management of comorbidities as an essential partner of immunosuppressive therapy, leading to comprehensive care of myositis patients and effective improvement of their quality of life.