CARD9 and fungal infectious disease: Caucasian and African populations have a high frequency of the minor allele of this polymorphism, 53 and 25%, respectively.[27] In humans, a homozygous mutation and thus loss of function of CARD9 is rare, with a single case report of a family having increased susceptibility to fungal infection in association with the CARD9 deficiency.[28] Heterozygous inheritance of the minor allele likely leads to a change of function of the CARD9 signaling pathway.