PLCG2 and Familial cold urticaria: AiUD is linked to CAPS, including familial cold-induced autoinflammatory syndrome (FCAS), Muckle-Wells syndrome (MWS) and chronic infantile neurological cutaneous and articular (CINCA) syndrome, with NLRP3 mutations, FCAS2 with NLRP12 mutations, FCAS3 with PLCG2 mutations, FCAS4 with NLRC4 mutations, and Schnitzler syndrome without monogenic background (5).