BACKGROUND Systemic lupus erythematosus (SLE) is a systemic autoimmune disease resulting from dysregulation of the immune response. In genetically predisposed subjects, infections reputedly trigger an immune activation leading to autoimmunity and overt autoimmune diseases such as SLE. CASE REPORT We report the case of a 19-year-old woman who presented to our hospital reporting high-grade fever, dry cough, and polyarthralgia despite a course of empiric antibiotic and steroid therapy administered by her general practitioner (GP). On physical examination, she had a malar rash, a palpable erythematous maculopapular non-itchy rash over the limbs and trunk, and mild polyarthritis. A contrast computed tomography (CT) scan of the chest showed a pulmonary right upper-lobe consolidation with air bronchogram and multiple necrotizing conglomerate mediastinal lymph nodes. Culturing of collected samples from endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) of the mediastinal lymph node revealed growth of Mycobacterium kansasii. Antinuclear antibodies (ANA) and lupus anticoagulant (LAC) were positive. A diagnosis of M. kansasii infection associated with SLE was made. She was started on anti-mycobacterial and hydroxychloroquine therapy and entered into a joint rheumatological and infectious disease follow-up. Six months later, a CT scan with positron emission tomography (PET) showed a significant reduction in size of the basal right upper-lobe consolidation and hypermetabolic activity in multiple pulmonary areas and mediastinal lymph nodes. ANA and LAC tests were repeated and remained positive. The decision was made to continue the ongoing therapy course for 1 year in total. CONCLUSIONS Clinical and experimental studies have suggested the association of mycobacterial infections with SLE and as a possible infectious trigger of autoimmunity. We describe a unique case of M. kansasii infection associated with the onset of SLE in a young woman.