PLCG2 and acquired cold urticaria: Methods: Recent literature was reviewed to outline the clinical and molecular characteristics of familial atypical cold urticaria (FACU), familial cold autoinflammatory syndromes (FCAS; including NLRP3-, NLRP12-, NLRC4-, and PLCG2-related subtypes), FXII-associated cold autoinflammatory syndrome (FACAS), and familial predisposed acquired cold urticaria (FP-ACU).