[Solar urticaria: pre-PUVA UVA desensitization].
BACKGROUND: Solar urticaria is an uncommon disorder sometimes difficult to treat. It is characterized by the occurrence of typical whealing reactions on exposed skin a few minutes after sun exposure. The reactions resolve 1 to 5 hours after sun exposure ceases. We report a case evolving over several years, unresponsive to antihistamines and successfully treated by PUVAtherapy performed after UVA desensitization. CASE REPORT: For 3 years, a 22-year-old man developed erythema and itchy wheals at each solar exposure. The lesions appeared on all exposed areas including those usually exposed (face and hand) even in winter. An antihistamine regimen given for several weeks (cetirizine, loratadine) was ineffective. One trial of PUVA therapy led to an urticarial reaction of the entire body. Phototesting showed the minimal whealing dose for UVA was 0.4 J/cm(2). Phototherapy was therefore started by segmentary UVA irradiation at an initial dose of 0.1 J/cm(2). Exposure was then progressively increased allowing initiation of the PUVAtherapy on the 9(th) day with a dose of 0.5 J/cm(2) without whealing reaction. Slow increment PUVA therapy was able to induce good tolerance to sun exposure. DISCUSSION: Solar urticaria may sometimes have a deleterious effect on normal daily life. Severe cases are characterized by a whealing reaction after minimal sun exposure, even on regularly exposed skin. Antihistamines can provide some symptom relief in many patients, but high doses are required. If antihistamines are ineffective, PUVA therapy is indicated. Pre-PUVA UVA desensitization is often necessary. However, exposure to UVA alone has to be repeated every 24 to 48 hours to maintain the refractory state. The advantage of PUVA therapy is a more long lasting protection allowing weekly maintenance sessions.