Idiopathic Recurrent Serositis: A Multispecialty Challenge Resolved With Colchicine.

Idiopathic recurrent serositis (IRS) is a rare and diagnostically challenging condition characterised by recurrent inflammation of serous membranes, occurring without any identifiable infection, malignancy, or autoimmune cause. We present the case of a 32-year-old female who was initially admitted with dyspnoea and a right pleural effusion. Pleural fluid analysis revealed an exudate with negative microbiology, cytology, and tuberculosis testing, and she was treated empirically with antibiotics. Over the following months, the patient developed recurrent symptoms, including progressive abdominal distension due to gross ascites and a small pericardial effusion. An extensive multidisciplinary evaluation involving infectious disease, gynecology, respiratory medicine, and rheumatology yielded no definitive findings. Cross-sectional imaging and positron emission tomography (PET) excluded malignancy, while pleural and peritoneal biopsies demonstrated nonspecific chronic inflammation without granulomas, infection, or malignant cells. Extensive autoimmune, viral, and mycobacterial serological panels were negative. Intermittent cultures grew environmental organisms considered contaminants, and broad-spectrum antimicrobials did not alter the clinical course. Following referral to a national amyloidosis and autoinflammatory disease service, a diagnosis of IRS was suggested. The patient was started on colchicine, titrated from 500 mcg to 1.5-2 mg daily, alongside nonsteroidal anti-inflammatory drugs (NSAIDs) for breakthrough pain, resulting in marked clinical improvement, resolution of effusions, and sustained remission at follow-up, with return to normal activities. This report highlights the diagnostic complexity of recurrent serositis, where nonspecific clinical features and broad differentials often lead to extensive investigations and delays in effective treatment. Colchicine, through its anti-inflammatory effects on neutrophil function, provided durable control in this case, consistent with its established efficacy in familial Mediterranean fever and other autoinflammatory conditions. Clinicians should consider IRS in patients with unexplained recurrent effusions, and colchicine should be recognised as an effective first-line therapeutic option once secondary causes are excluded.