Gain-of-Function Mutations inSTAT1: A RecentlyDefined Cause for Chronic Mucocutaneous CandidiasisDisease Mimicking Combined Immunodeficiencies

Chronic Mucocutaneous Candidiasis (CMC) is the chronic, recurrent, noninvasive Candida infections of the skin, mucousmembranes, and nails. A 26-month-old girl was admitted with the complaints of recurrent oral Candidiasis, diarrhea, andrespiratory infections.Candida albicansgrew in oral mucosa swab. CMV and EBV DNA titers were elevated. She had hypergam-maglobulinemia; IgE level, percentages of lymphocyte subgroups, and in vitro T-cell proliferation responses were normal. She hadparenchymal nodules within the lungs and a calcific nodule in the liver. Chronic-recurrent infections with different pathogensleading to significant morbidity suggested combined immunodeficiency, CMC, or Mendelian susceptibility to mycobacterialdiseases. Genetic analysis revealed a predefined heterozygous gain-of-function mutation (GOF) (c.1154 C>T, p.Thr385Met) in thegene coding STAT1 molecule. Hematopoietic stem cell transplantation (HSCT) was planned because of severe recurring infections.Patients withSTAT1GOF mutations may exhibit diverse phenotypes including infectious and noninfectious findings. HSCT shouldbe considered as an early treatment option before permanent organ damage leading to morbidity and mortality develops. This caseis presented to prompt clinicians to considerSTAT1GOF mutations in the differential diagnosis of patients with chronic Candidiasisand recurrent infections with multiple organisms, since these mutations are responsible for nearly half of CMC cases reported.