Connective tissue disease--associated interstitial lung disease: an underreported cause of interstitial lung disease in Sub-Saharan Africa.

Interstitial lung disease (ILD) occurs in 15% of connective tissue disease (CTD) patients causing considerable morbidity and mortality. Data is scarce regarding its clinical characteristics and outcomes in Africa. We aim to study the frequency, clinico-radiological characteristics, and treatment outcomes of African CTD-ILD patients. A retrospective cross-sectional study of ILD among 318 CTD patients diagnosed using relevant ACR criteria at the rheumatology unit of Lagos State University Teaching Hospital (LASUTH), Lagos from 2012 to 2019. Socio-demographics, clinical features, radiological findings, and treatment outcomes were documented. Data was analyzed using SPSS version 21 with p < 0.05. The LASUTH ethics committee approved the study. Interstitial lung disease occurred in 31 (9.7%) of 318 CTD cases. Their mean age was 38.8 ± 13.3 years, range 19-68 years with 28 (90.3%) females. Proportions of CTD-ILD were Sjogren's syndrome (50%), UCTD (50%), systemic sclerosis (46.7%), MCTD (33.3%), PM/DM (25%), SLE (6.5%), and RA (2.6%). Commonest presentations were cough (93.5%) and bibasal inspiratory crackles (83.9%) with a restrictive pattern in 83.9%. Antinuclear antibody occurred in 100% and anti-ENA in 67.7%. Traction bronchiectasis (89.7%) and ground glass opacities (96.6%) were frequent HRCT findings. Treatments included pulse-dose prednisolone, cyclophosphamide, mycophenolate mofetil, pirfenidone, and rituximab. Outcomes were ambulatory oxygen therapy (12.9%) and mortality (16.1%) with 9.7% lost to follow-up. CTD-ILD is a female predominant disease occurring in 9.7% of CTD patients mostly those with Sjogren's syndrome and systemic sclerosis. Due to significant morbidity and mortality, we advocate routine ILD screening for all CTD patients including those with undifferentiated disease. Key Points: • Interstitial lung disease occurs in 9.7% of patients with underlying connective tissue disease. • Females are predominantly affected especially those with Sjogren's syndrome and systemic sclerosis. • Mortality occurs in roughly 1 in every 6 patients with CTD-ILD.