HYPEREOSINOPHILIA LEADS TO PRIMARY IMMUNODEFICIENCY DIAGNOSIS

Abstract

<h3>Introduction</h3> In the absence of prior infections, idiopathic hypereosinophilia should prompt consideration of a primary immunodeficiency (PID). <h3>Case Description</h3> We present an 8-month-old previously healthy male admitted for persistent hypoxia and suspected bronchiolitis. This patient did not present with fever, weight loss, adenopathy, chronic rash, GI symptoms, or medication use. There was no travel history, sick contacts, or pertinent family history. Laboratory results were significant for negative viral panel and absolute eosinophil count > 34,000. Chest CT showed scattered ground glass opacities without cavitation or bronchiectasis. Bone marrow biopsy was negative for malignancy. T cell (beta) and B cell gene rearrangement studies were negative, as well as FIP1L1-PDFGFRA, FISH studies, and myelodysplastic panels. Cardiac workup, infectious/parasitic tests, tryptase, and B12 levels were normal. The patient was started on systemic steroids with dramatically improved hypereosinophilia. Workup revealed low IgG/IgA levels, with normal IgM. Vaccine titers to tetanus, diphtheria and Hib were absent, despite up-to-date immunizations. Genetic testing revealed a pathogenic mutation in the CD40L gene, indicating X-linked hyper IgM syndrome (HIGM). Pneumocystic jirovecii was confirmed with bronchoscopy. TMP-SMX treatment allowed for weaning off steroids. The patient was started on IVIG and is awaiting bone marrow transplant. <h3>Discussion</h3> HIGM often presents in infancy with increased susceptibility to sinopulmonary infections. Unlike other PIDs with clinical manifestations of atopy, HIGM does not often present with eosinophilia. Opportunistic infections, including PJP, may drive eosinophil production through antigenic stimulation of TH2 cells. This case illustrates the importance of immunologic considerations in patients with unexplained hypereosinophilia, even without a significant infectious history.