Phospholipase C gamma (PLCg), also known as 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase gamma, is a member of the family of phosphoinositide specific PLCs that convert phosphatidylinositol 4,5-bisphosphate into second messengers 1,2-diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3), thereby initiating and propagating numerous cellular signaling events.There are two forms of phospholipase C-gamma, PLCg1 and PLCg2. PLCg1 is widely distributed but the expression of PLCg2 is primarily limited to cells of haematopoietic lineage. PLCg1 is critical in many cells, and in haematopoietic systems it is required for T cell and NK cell function, whereas PLCg2 is important in mast cells, NK cells, B cells, and platelets. This entry represents PLCg2. Mutations in PLCg2 gene cause familial cold autoinflammatory syndrome 3 (FCAS3), whcih is an autosomal dominant immune disorder charactersed by the development of cutaneous urticaria, erythema, and pruritis in response to cold exposure. Mutations in PLCg2 gene also cause autoinflammation, antibody deficiency, and immune dysregulation PLCG2-associated (APLAID), which is an autosomal dominant systemic disorder characterised by recurrent blistering skin lesions with a dense inflammatory infiltrate and variable involvement of other tissues.