Polyserositis as an early presentation of systemic lupus erythematosus in an elderly patient: diagnostic challenges and clinical implications

Abstract

Systemic lupus erythematosus (SLE) is an autoimmune disorder with multisystem involvement, predominantly affecting young women. Diagnosis after the age of 50 years is rarely encountered, and late-onset SLE frequently presents with atypical features that differ markedly from classic manifestations. Polyserositis-defined as simultaneous inflammation of the pleura, peritoneum, and pericardium-is an uncommon and often under recognised presentation of SLE, particularly in elderly patients. We report a 70-year-old woman with no known comorbidities who presented with bilateral symmetric polyarthritis (small joint predominant), non-scarring alopecia, moderate pleural and pericardial effusion, ascites, bilateral pitting pedal oedema, and proteinuria. On investigation, ANA was strongly positive (3+, titre 1:720) with positivity for anti-dsDNA, anti-nucleosome, anti-Smith, and anti-U1RNP antibodies, along with low complement levels (C3 and C4), fulfilling ACR criteria for SLE. Infectious and malignant aetiologies were systematically excluded. The patient was initiated on pulse methylprednisolone followed by oral prednisolone, mycophenolate mofetil, diuretics, and albumin transfusion, with marked clinical improvement. At two-month follow-up, proteinuria had reduced significantly (900 mg/day to 190 mg/day) and repeat chest imaging confirmed bilateral clear lung fields. This case highlights the importance of including SLE in the differential diagnosis of unexplained polyserositis in elderly patients, where classical mucocutaneous features may be absent. Polyserositis in SLE may indicate severe systemic inflammation requiring careful therapeutic monitoring. Increased awareness, application of evidence-based guidelines, and early rheumatology referral are key to timely diagnosis and improved outcomes in this patient group.