Hypersensitivity reactions
Dermatologic ADRs are difficult to be distinguished as a side effect of or an allergic reaction to these drugs or a flare of the underlying dermatological disease (87,88). The most common manifestation is mild pruritic MPEs within initial 4 weeks of treatment (87). High association with AGEP [OR: 39 (8-191)] was described (89). Cases of DRESS (90,91), pustular DRESS (92), erythema multiforme (93), bullous erythema (94), SJS/TEN (95-97), photoallergic dermatitis (98), and occupational contact dermatitis (99) have been reported.
PTs are reported to be useful for the diagnosis of NIHRs (93,95,100), confirming a T-cell mediated mechanism. However, in a series of 14 patients with ADRs due to chloroquine/hydroxychloroquine, skin tests (STs) were negative in all cases (87). DPT is useful in non-severe cutaneous ADRs in order to differentiate allergic reactions from dermatological adverse effects since only 30% of the patients reporting cutaneous ADRs reveal a positive DPT (87). Successful desensitization protocols of hydroxychloroquine in MPE were reported (101-104). Recently, a 5-hour desensitization protocol for non-immediate urticaria was successfully administered (105).
Two cases of IHR were reported (106,107) and one was confirmed by SPTs (106), however there are no available data for in vitro diagnosis. A hydroxychloroquine desensitization procedure that enables the turning of positive SPTs into negative was published (106). In a case of anaphylaxis a 7 day-desensitization procedure was successfully performed with premedication (107).