The spectrum of idiopathic inflammatory myopathies in South Africa

Introduction There are many reports on idiopathic inflammatory myopathies (IIM) but little information from sub-Saharan Africa. We conducted a retrospective study of IIM in a multi-ethnic cohort seen at a single centre in Durban, South Africa. Method The study included patients who fulfilled the Bohan and Peter or European League Against Rheumatism/American College of Rheumatology criteria for IIM. The information recorded included demographic data, clinical findings, results of investigations, treatment and outcome. Patients with overlap myositis (OM) had myositis and criteria for another connective tissue disease. Results There were 104 patients with IIM; 82.7% female and 70.2% African blacks. They included 41 (39.4%) with OM, 26 (25%) polymyositis (PM), 26 (25%) dermatomyositis (DM), six (5.8%) juvenile dermatomyositis and five (4.8%) cancer-associated myositis. Our patients had a younger mean age at diagnosis (36.8 +/- 14.7 years) compared with 45-55 years in most other studies. Scleroderma-myositis overlap accounted for 26 (63.4%) of the patients with OM. Patients with OM were significantly younger than PM (p = 0.004) and DM (p = 0.044) and had lower, but not statistically significant, creatine kinase levels at diagnosis compared with PM (p = 0.052) and DM (p = 0.073). Interstitial lung disease was more common in OM (p = 0.001) and PM (p = 0.024) than DM. Oropharyngeal weakness was more common in DM than OM (p = 0.001) and PM (p = 0.032). African blacks were younger (p = 0.028) at diagnosis and had more cardiac abnormalities (p = 0.034) than Indians. Conclusion The spectrum of IIM in our cohort of mainly African blacks is similar to other studies, with OM being the most frequent subtype.

Automated summary

This retrospective study of idiopathic inflammatory myopathies (IIM) in a multi-ethnic cohort in Durban, South Africa found that overlap myositis (OM) was the most frequent subtype. African blacks in the cohort were diagnosed at a younger age and had more cardiac abnormalities compared to Indians.