PRKCD and Immunodeficiency: Biallelic loss-of-function mutations in PRKCD, the gene encoding PKCδ, either result in PKCδ deficiency or affect its phosphorylation; in addition, these mutations cause immunodeficiency with variable immunoglobulin values and consistently reduced counts of class-switched memory B cells, characterized by immune dysregulation.170–173 Six patients from four unrelated families have been reported to develop disease as a consequence of biallelic PRKCD mutations.