Clinical allergy. Managing generalized interferon-induced eruptions and the effectiveness of desensitization.

Background: We evaluated the value of skin tests and the efficacy of a 12-step desensitization protocol to pegylated interferon (IFN) in patients with generalized drug eruptions due to IFNs.

Methods: A retrospective study (1998-2009) was followed by a cross-sectional clinical study conducted prospectively (2009-2011). All patients received a dermatological clinical examination and skin tests. Twelve-step IFN desensitization was proposed for patient with active hepatitis C and no alternative therapy.

Results: Twenty-six patients (13 males, mean age, 53.5 years) had generalized reactions to IFNs; 21 were treated with IFN-α and 5 with IFN-β. Moreover, 21 patients had skin tests. Intradermal tests (IDTs) were positive after an average of 72 h. Cross-reactivity between peg-IFN-α2a and peg-IFN-α2b was observed in 5/10 cases in the prospective study. In 16 of 26 cases, IFN treatment was stopped. In 8 of 16 cases of diffuse eczematous drug eruption, treatment was continued. The corticosteroid and antihistamine were sufficient in 4/8 cases. In three other cases, topical tacrolimus was highly effective. In 3 of 16 cases in which treatment were stopped, patients underwent the early resumption of peg-IFN-α. These three patients had positive tests with peg-IFN-α2a and peg-IFN-α2b and successfully completed the tolerance induction protocol for peg-IFN-α2b. Tolerance induction involved a weekly dose of peg-IFN and a gradual increase in the recovery of an antiviral C. Clinical tolerance was excellent, and the patients' viral load C became negative.

Conclusions: Our study demonstrates the benefit of allergy testing in cases of generalized drug reactions to IFN, cross-reactivities in a single class of IFNs and the importance of delayed IDT reading. We report for the first time the effectiveness of 12-step desensitization with peg-IFN.