Non-tuberculous mycobacterial infection in patients with systemic lupus erythematosus

Objectives. Patients with systemic lupus erythematosus (SLE) are susceptible to opportunistic infections. To examine the clinical manifestations of non-tuberculous mycobacterial (NTM) infections with those of Mycobacterium tuberculosis (MTB) infections in SLE patients. Methods. Medical records of a cohort of 725 SLE patients were reviewed for previous NTM infections. Demographic characteristics, predisposing factors and clinical outcomes were compared with patients who had previous MTB infections (n=39). Results. Eleven ( nine female and two male) cases were identified ( prevalence 1.5%). The mean +/- S.D. age at the time of infection was 42.8 +/- 13.9 yrs, 9.3 +/- 5.8 yrs after the onset of SLE. The mean +/- S.D. time taken from onset of symptoms to the diagnosis of NTM infection was 5.7 +/- 7.2 months. Sites of involvement included skin and soft tissue (n=8), chest (n=2) and disseminated infection (n=1). NTM infections were more likely to involve extrapulmonary sites (P=0.006), presented in patients with longer lupus disease duration (P < 0.001), occurred in older patients (P < 0.001) and in those who had a higher cumulative dose of prednisolone (P=0.01) than MTB infections. Using a stepwise logistic regression, disease duration was found to be the only independent predictive factor (P=0.005) for NTM infections. Ten (25.6%) patients with MTB infections but none of the patients with NTM infections presented concomitantly at the onset of SLE (P=0.09). There were no differences in the recurrence rate (P=0.64) and frequency of disseminated infections (P=0.40) between NTM and MTB infections. Conclusions. NTM infections tended to develop in SLE patients later in their disease course than MTB infections. A high index of suspicion is required for its diagnosis.