MAKING A STAT DIAGNOSIS IN A PATIENT PRESENTING WITH VILLOUS ATROPHY

Abstract

<h3>Introduction</h3> Signal transducer and activator of transcription 1 (STAT1) gain-of-function (GOF) gene mutations are highly penetrant, resulting in enhanced STAT1-dependent responses to interferon-alpha/beta and interferon-gamma signaling, and impaired Th17 development. This manifests as recurrent infections, cytopenias, and autoimmune disease. Herein, we present a case of a child diagnosed with a STAT1 mutation. <h3>Case Description</h3> A 3-year-old female presented for secondary evaluation of persistent gastrointestinal and respiratory symptoms, recurrent sinopulmonary and skin infections, failure to thrive, and developmental delay. An esophagogastroduodenoscopy performed elsewhere showed increased duodenal intraepithelial lymphocytes with crypt hyperplasia and villous atrophy. Testing for Celiac disease and autoimmune enteritis were negative. Chest computed tomography showed bilateral bronchiectasis with mucous plugging. Bronchoalveolar lavage culture was positive for Streptococcus pneumoniae. Laboratory workup was notable for anemia and T-cell lymphopenia. Quantitative lymphocytes showed a low CD3+ count of 446 cells/mcL, low CD4+ count of 185 cells/mcL, and low CD8+ count of 194 cells/mcL. Lymphocyte proliferation to antigens showed essentially absent total CD45+ lymphocytes and CD3+ T cell responses to Candida and Tetanus toxoid antigens. Genetic testing later revealed a heterozygous, pathogenic c.1154C>T (p.Thr385Met) variant in the STAT1 gene. Additional testing for Th17 enumeration showed a decreased IL17 and Th17 cell percentage. She was treated with supportive care, antibiotics, and referred to Medical Genetics for additional education and counseling. <h3>Discussion</h3> STAT1-GOF gene mutations are rare and associated with variable phenotypes and disease severity. Genetic testing can help determine the cause of complex, multisystem diseases. Stem cell transplant, immunoglobulin replacement therapy, and JAK inhibitors are potential treatment considerations.