A Case of HUPRA (Hyperuricemia, Pulmonary Hypertension, Renal failure, Alkalosis) with Immune Dysfunction

Introduction Hyperuricemia, pulmonary hypertension, renal failure, alkalosis (HUPRA) syndrome is a mitochondrial disease caused by mutations in SARS2 (seryl-tRNA synthetase 2), which plays a role in protein synthesis. Limited case reports describe an association of HUPRA with immunodeficiency; however, no in-depth immune phenotyping has been described. We present a case of HUPRA with recurrent infections and lymphopenia, with clinical improvement on immunoglobulin replacement therapy (IgRT). Case Description An 11-month-old male born at 29 weeks’ gestational age with pulmonary hypertension (PH) and tracheostomy dependence was admitted with recurrent fevers and worsening PH. History revealed prior Enterococcus faecalis bacteremia as well as Staphylococcus aureus and Pseudomonas aeruginosa tracheitis. Laboratory evaluation revealed mildly low IgG with normal IgM and IgA. Lymphocyte subsets revealed T cell, B cell, and natural killer cell lymphopenias, with CD4+ T cell compartment skewing to a memory phenotype, normal total switched memory B cells, and normal T follicular helper cells. Vaccine titers were not obtained, given receipt of only one set of vaccines. T cell proliferations were reassuring. Genetic testing revealed compound heterozygous mutations in SARS2, confirming a diagnosis of HUPRA. He is being treated with IgRT with significant clinical improvement. Discussion In case series, up to half of patients with HUPRA can present with increased infections, often with leukopenia. Multiple studies have shown that aminoacyl-tRNA synthetases can play a role in immune cell development, regulation, and autoimmunity through interactions with innate and adaptive immune responses. Additionally, hyperuricemia is known to induce innate and adaptive immune responses. It is difficult to know how these findings relate to the function of SARS2 or patients with HUPRA. Our patient was found to have multilineage lymphopenia with mildly low IgG, with significant clinical improvement on IgRT. More in-depth evaluations are needed to better understand the pathophysiology of immune dysfunction with SARS2 deficiency. This case provides in-depth immune phenotyping and a potential treatment option for others with HUPRA. Tabular data are included as downloadable supplement files.