Postpartum Immune Reconstitution Inflammatory Syndrome Presenting as Massive Bilateral Pleural Effusion in a Previously Healthy Woman: A Case Report.

Immune reconstitution inflammatory syndrome (IRIS) is commonly described in individuals recovering from immunosuppression, particularly in HIV-positive patients initiating antiretroviral therapy. However, a similar rebound phenomenon can occur postpartum, a period marked by a shift from an immunotolerant to a pro-inflammatory state. IRIS in this context is underrecognized and may present atypically, complicating timely diagnosis. We report the case of a 35-year-old South Asian woman (G2P2), previously healthy, who developed severe respiratory symptoms within 48 hours postpartum following a planned cesarean section. Despite unremarkable perinatal screening and a smooth surgical course, she experienced an acute onset of breathlessness and dry cough. Imaging revealed massive bilateral pleural effusions with partial lung collapse. Extensive workup ruled out common infectious, thromboembolic, cardiac, and autoimmune etiologies. A therapeutic thoracentesis and empirical treatment with corticosteroids and broad-spectrum antimicrobials led to rapid improvement. Based on the clinical course and exclusion of alternative diagnoses, a diagnosis of postpartum IRIS was considered. This case underscores the importance of considering IRIS in the differential diagnosis of unexplained systemic inflammatory responses in postpartum patients. The postpartum period represents a vulnerable window due to the abrupt immune reconstitution that occurs after childbirth. Early recognition of this entity is crucial for effective management and for preventing unnecessary invasive interventions.