Urticaria in a Term Infant with CHARGE Syndrome

Urticaria is typically characterized by an acute onset of wheals and flares, which are small areas of dermal swelling. Exposure to the allergen activates the release of a multitude of inflammatory mediators including cytokines, histamine, leukotrienes, prostaglandins, and platelet-activating factors. (1) Mast cell activation occurs through cross-linking of immunoglobulin E (IgE) molecules following the cells' exposure to an antigen/allergen (Fig 2). (2) Cross-linking of IgE occurs through high-affinity binding to high-affinity IgE receptors (FceRI). When 2 IgE molecules bind to the same antigen or its receptors, they become cross-linked, which allows for kinase activation and subsequent phosphorylation of cytoplasmic motifs on the b and g receptor chains of the antigen. Through specific intracellular signal transduction pathways, mast cells are then activated, resulting in a release of cytoplasmic histamine, heparin, and proteases.