Chronic mucocutaneous candidiasis (CMC) is a heterogenous group of primary immunodeficiency diseases characterized by chronic and recurrent Candida infections primarily involving the nails, skin and mucous membranes. Impaired IL-17 T-cell immunity is known to be one of the mechanisms of this disease, as Th17 cells and their effector cytokines IL-17 and IL-22 have critical functions for candidial host defense via epithelial cells. Gain-of-function (GOF) mutations in the human signal transducer and activator of transcription 1 (STAT1) gene cause an impaired Th17 cell production and can cause CMC.
A two-year-old girl presented to our hospital at the age of 1,5 years with failure to thrive, recurrent bacterial respiratory tract infections, diarrhea and recurrent oral thrush, not responding well to local treatment. Oral mucosa swab repeatedly showed Candida albicans. She was born as the second child of healthy, non-consanguineous parents of Serbian origin. Initial immunological screening revealed a normal white blood cell count and normal serum immunoglobulines. Response to vaccination with Pneumovax 23 was normal. Further workup showed normal T cells with low Th17 cell counts (0,08% of CD4 T cells) and impaired T cell function. Subsequently a genetic workup was performed which showed a GOF mutation in the STAT1 gene. This mutation is reported to be pathogenic for CMC.
Recurrent oral Candidiasis after the age of one year is an alarm sign and indicative for immunodeficiency disorders such as CMC. It is important to perform an immunological workup including genetic testing for the involved genes in such cases.