Unravelling Granulomatous-Lymphocytic Interstitial Lung Disease: A Case of Common Variable Immunodeficiency With Unusual Clinical Features and Response to Intravenous Immunoglobulin.

Granulomatous-lymphocytic interstitial lung disease (GL-ILD) is a rare pulmonary complication associated with common variable immunodeficiency (CVID), complicating diagnosis due to overlapping symptoms with other chronic respiratory conditions. This case involves a 33-year-old male with a history of sarcoidosis, presenting with recurrent sino-pulmonary infections, mediastinal and axillary lymphadenopathy, and significant splenomegaly. Despite initial treatment with prednisolone, his symptoms persisted, and FDG-PET imaging showed metabolic activity in the sinuses and lymph nodes. Immunological assessment revealed markedly reduced immunoglobulin levels, leading to intravenous immunoglobulin (IVIG) therapy, which resulted in substantial improvement. A critical learning point is recognising that splenomegaly is commonly associated with CVID, which can aid in distinguishing it from other conditions. This case underscores the importance of considering CVID, with or without GL-ILD, as a differential diagnosis in patients with persistent respiratory symptoms and granulomatous lung disease, including sarcoidosis. Further research is needed to optimise treatment strategies for this rare condition.