Hypersensitivity reactions
Cutaneous eruptions induced by IFNs are common, with an incidence of 13-23% (111,112). Localized reactions at injection sites are most frequent at 48 weeks (113). Diffuse skin symptoms including urticaria, generalized eczema, papules are common and mostly treated with symptomatic treatment (111,114,115). Among 26 patients with non-immediate reactions to IFNs, 12 cases reported generalized eczema, 10 MPE, 3 generalized urticaria and 1 lichenoid eruption (116). Cases of FDEs (117), and subacute cutaneous lupus (118) were described.
There are few case reports of immediate urticaria (119,120) and anaphylaxis (121,122). For IHRs to IFN-β, positive STs were reported (119,121). For NIHRs, PTs have a low value and are not recommended, whereas delayed reading IDTs are useful (116,123). A positive DPT was reported in a patient experiencing anaphylaxis due to peg-INF-α2a with negative STs (122). Successful desensitization protocols both for IHRs (120) and NIHRs (116,124) due to different IFNs were reported.