Chronic mucocutaneous candidiasis and immune dysregulation due to STAT1 Gain of Function

Abstract

BackgroundGermline gain-of-function (GOF) mutations in the Signal Transducer and Activator of Transcription 1 (STAT1) gene have been associated with autosomal dominant chronic mucocutaneous candidiasis (CMCC), autoimmune and inflammatory manifestations. Although most patients with STAT1 GOF have CMCC, the disease has a broad phenotypic spectrum.Case Description: A 13-year-old male born to non-consanguineous parents with a past medical history of chronic mucocutaneous candidiasis, autoimmune hypothyroidism, and recurrent viral respiratory tract infections presented for immune evaluation. His medical history was also significant for chronic fatigue refractory to thyroid replacement therapy, chronic paronychia, oral thrush, pneumonia requiring hospitalization, recurrent chalazia status post excision, and prolonged tonsillitis. Laboratory results showed high total serum IgG levels with elevated IgG1 and IgG3 subclasses, elevated B cell counts with atypical lymphocytes, and chronic EBV-viremia. He had no clinical or laboratory evidence of active lymphoproliferative disease. He had normal lymphocyte proliferation to mitogens with impaired response to antigens. He had an adequate humoral response to protein and polysaccharide antigens. Targeted genetic testing for inborn errors of immunity showed a heterozygous variant in the STAT1 gene (c.1169T>C, p.MET390Thr), which had been previously reported in patients with STAT1 GOF. The patient was treated with oral fluconazole with interval improvement in CMCC and subsequently maintained on prophylactic fluconazole and TMP/SMX. He had an unremarkable family history, which suggests a de novo mutation in STAT1. ConclusionThe presence of CMCC and autoimmunity should raise concern for STAT1 GOF. Genetic testing for inborn errors of immunity can be a valuable tool in the diagnosis of patients with CMCC and can help guide therapy. Unfortunately, hematopoietic stem cell transplant has been associated with a high mortality rate in patients with STAT1 GOF. JAK inhibition therapy was recommended for this patient. However, there is currently no consensus regarding JAK inhibitor selection, dosing, treatment duration or biomarkers in STAT1 GOF.