Occult Late-Onset Systemic Lupus Erythematosus Presenting as Critical Multisystem Disease in a Male: A Diagnostic Challenge in the Intensive Care Unit.

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease that predominantly affects women of reproductive age. Late-onset SLE in males is uncommon and frequently presents with atypical clinical features, often resulting in diagnostic delay. We report a 60-year-old male admitted to the intensive care unit (ICU) with melena and haemodynamic instability on a background of a recent non-ST-elevation myocardial infarction (NSTEMI). During investigation, severe esophageal candidiasis, bilateral pleural effusions, proteinuria, microscopic haematuria, and widespread cutaneous lesions were identified. Extensive infectious and malignancy screening was negative. Autoimmune testing demonstrated strongly positive antinuclear antibodies (ANA), high-titre anti-double-stranded DNA antibodies (anti-dsDNA), positive extractable nuclear antigen (ENA) profile, hypocomplementemia, and lupus anticoagulant positivity. Skin biopsy was suggestive of subacute cutaneous lupus erythematosus (SCLE). The patient fulfilled the 2019 European Alliance of Associations for Rheumatology/American College of Rheumatology (EULAR/ACR) classification criteria for SLE. Treatment with pulse intravenous methylprednisolone followed by oral corticosteroids and hydroxychloroquine resulted in significant clinical improvement. This case highlights the diagnostic complexity of late-onset male SLE presenting with critical multisystem disease in the ICU and emphasises the importance of considering autoimmune disease in patients with unexplained multisystem inflammatory manifestations.