Chronic mucocutaneous candidiasis associated with a novel frameshift mutation in IL-17 receptor alpha

Background: Chronic mucocutaneous candidiasis (CMCC) has traditionally encompassed endocrinopathy, autoimmunity, and infection of the skin, nails, oral and genital mucosa. It is typically caused by Candida albicans, an organism that is found to be commensal in healthy individuals. To date, most patients with CMCC have mutations in AIRE or STAT1. While chronic Candida spp. infection is a feature of multiple profound T cell deficiencies, it has also been identified in rare cases involving selective immune defects, including interleukin-17 receptor A (IL-17RA) deficiency. An association between Staphylococcus aureus infections and candidiasis due to IL-17RA deficiency has recently been proposed. Aim: We sought to identify the genetic defect in a patient presenting with recurrent oral thrush and S. aureus infections, but otherwise unremarkable immune workup. Methods: Whole exome sequencing and Sanger confirmation was performed, and protein expression analysis utilized to assess the impact of the genetic aberration. A comprehensive immune workup was completed to characterize any possible deficits in his immune system. Results: Next generation sequencing techniques identified a homozygous mutation in IL17RA, c.1696insAG, resulting in the frameshift mutation p.Q566fs. Western blot analysis confirmed the loss of IL-17RA expression. Conclusion: We describe here a novel frameshift mutation in IL17RA. Clinically, the patient was a diagnostic challenge as he did not present with a classic CMCC phenotype. This case emphasizes the importance of genetic analysis in patients presenting with recurrent infections. Statement of novelty: We identify a novel frameshift mutation in IL17RA in a patient presenting with recurrent bacterial and fungal mucocutaneous infections.