Photochemotherapy with oral or topically applied psoralens, usually methoxsalen, and UV-A is a widely accepted treatment modality for various chronic inflammatory and lymphoproliferative skin disorders, such as psoriasis and eczema.1 We prescribed a thrice-weekly home psoralen–UV-A treatment to a 54-year-old man (weight, 81 kg) with severe disabling tylotic hand eczema. The treatment consisted of a commercially available UV-A bronzing unit and 50 mg of methoxsalen (Geroxalen). Pretreatment laboratory evaluation of blood and urine samples for renal, liver, and hematological parameters revealed no abnormalities. Between 1 and 2 hours after taking the methoxsalen, along with a meal, the patient experienced nausea and dyspepsia, which increased in severity after every subsequent intake and lasted for about 20 to 30 hours. We then recommended that he use acetaminophen and reduce his methoxsalen dose to 20 mg ×2 with a 15-minute interval, but the change in his regimen was of no benefit. After the fifth administration of methoxsalen, he rapidly developed a severe headache, nausea and vomiting, fatigue, dyspepsia, muscle aches, and a temperature of 38.2°C, all of which lasted about 40 hours. His complaints were attributed to a "case of the flu," and the psoralen–UV-A treatment was temporarily discontinued. When the same symptoms recurred even more severely after the sixth intake of methoxsalen 1 week later, a causal relationship with the drug was suspected. We reintroduced the use of methoxsalen along with testing of the patient's blood and urine samples, monitoring of his temperature, and supervised documentation of his symptoms. Before ingesting 40 mg of methoxsalen, he felt well. One and a half hours later, he started to complain of nausea and dyspepsia, followed by the above-mentioned symptoms, without vomiting however. His temperature reached a maximum of 39.0°C the following morning. Tests of blood and urine samples showed no abnormalities. The symptoms lasted for 48 hours.
van Coevorden AM, Coenraads P. Severe Influenzalike Symptoms Associated With Methoxsalen Photochemotherapy. Arch Dermatol. 2002;138(6):840-841. doi:10.1001/archderm.138.6.838