LATE-ONSET COMBINED IMMUNE DEFICIENCY IN A PATIENT WITH ADENOSINE DEAMINASE GENE MUTATION

Abstract

<h3>Introduction</h3> We report on a 25-year-old man with a history of recurrent pneumonia and large joint infections who was found to have T cell dysfunction with B cell lymphopenia and a heterozygous adenosine deaminase(ADA) gene mutation. <h3>Case Description</h3> The patient has had three large joint infections and three-to-four episodes of pneumonia in his life. He is without other prior medical condition or family history of immune deficiency. He presented to the ER with tachycardia and left knee swelling. He was found to have pseudomonas bacteremia of unknown source for which he was treated. Due to his tachycardia, he had a chest CT to evaluate for pulmonary embolism which revealed found incidental bronchiectasis. Evaluation for immune deficiency was initiated and he was found to have IgA <10 mg/dL, IgG <75, and IgM <20, CD4 count 202 cells/uL, CD8 596, low response to polysaccharide and protein vaccines. HIV testing was negative. We then pursued genetic testing. Patient was found to carry a single pathogenic variant in the ADA gene. Loss of function variants in this gene are associated with severe combined immunodeficiency, but a second variant was not identified. Our patient is doing well on IVIG without further infections. <h3>Discussion</h3> To our knowledge, our patient is the first reported to be a carrier for a pathogenic ADA gene mutation and presenting with a clinical phenotype of B cell lymphopenia and T cell dysfunction. A more complete understanding of the underlying genetic causes for late-onset combined immune deficiency is needed as well as any correlation with ADA deficiency.