A case of adult-onset X-linked lymphoproliferative disease mimicking pulmonary infection.

X-linked lymphoproliferative disease (XLP) is a rare primary immunodeficiency with susceptibility and vulnerability to Epstein-Barr virus (EBV) infection. Most patients were diagnosed in early childhood and do not survive into adulthood. Here we reported an adult-onset XLP patient presenting with fever, dyspnea, and pulmonary nodules, mimicking respiratory infection at disease onset. Diagnosis was made based on whole-exon sequencing and pedigree analysis. Chest CT showed bilateral nodular lesions partially responsive to steroid therapy. The symptoms were managed with high-dose steroid, together with broad-spectrum anti-infective treatment for mixed secondary opportunistic infections. Pathology studies revealed non-Langerhans histiocytosis and T cell infiltration in lungs. Our case highlights the importance of genetic sequencing in managing young patients with unexplained infection and potential immuno-deficiency. We also added to the understanding of XLP by carrying detailed investigation into the pulmonary lesions.