Pulmonary manifestations of the idiopathic inflammatory myopathies in a South African population.

Background: Pulmonary complications cause significant morbidity and mortality in patients with idiopathic inflammatory myopathies (IIMs).

Objectives: To describe the frequency and spectrum of pulmonary complications in patients with IIMs in South Africa (SA).

Methods: A retrospective records review of adult patients with IIMs or clinically amyopathic dermatomyositis (CADM) presenting with respiratory complaints at a tertiary care facility in SA was performed. Clinical features, results of laboratory and pulmonary function tests (PFTs), radiological findings and treatment were recorded.

Results: Pulmonary complications were documented in 66 patients. Most patients (n=41; 62.1%) had dermatomyositis, 14 (21.2%) had polymyositis, and 3 (4.5%) had CADM. There were 8 patients with overlap syndromes. Dyspnoea and a dry cough were the most common presenting symptoms, in 52 (78.8%) and 36 (54.5%) patients, respectively. Bibasal crackles were noted in 38 patients (57.6%). Interstitial lung disease (ILD), followed by infection and pulmonary hypertension (PH), were documented in 46 (69.7%), 16 (24.2%) and 9 (13.6%) patients, respectively. Nine patients had microbiologically confirmed pulmonary tuberculosis. Patients who were anti-Jo1 antibody positive (n=16) had higher levels of acute inflammatory markers and muscle enzymes compared with the rest of the patients (p<0.0001). Dyspnoea and bibasal crackles were associated with significantly lower baseline and 12-month lung function parameters. Nonspecific interstitial pneumonia was the most common radiological pattern of ILD, present in 25 (62.5%) of the patients with ILD.

Conclusion: ILD was the most prevalent complication in this study of SA patients with IIMs. Pulmonary infections and PH were also significant contributors to morbidity. The presence of dyspnoea and crackles was predictive of lower baseline PFTs in this population.

Study Synopsis: Pulmonary complications, including interstitial lung disease (ILD) and infections, are significant contributors to morbidity and mortality in patients with idiopathic inflammatory myopathies (IIMs). There is very little research currently available to describe the spectrum of pulmonary manifestations in these patients in an African setting, a lack that this study aimed to address. ILD was the most common pulmonary complication in patients with IIMs in this cohort. Signs and symptoms of ILD may be present before symptoms of myositis, and dyspnoea and a dry cough were shown to be predictive of reduced lung volumes. Patients with IIMs on immunosuppressive therapy in our setting are at high risk of infection, particularly tuberculosis.