Photosensitivity to simvastatin with an unusual response to photopatch and photo tests

A 50-year-old woman was seen in April 1993 with erythema and vesicles on sun-exposed areas that had started a week before. She had no previous history of atopic dermatitis or photosensitivity. She had been taking simvastatin 5 mg t.d.s. orally for 3 weeks for hypercholesterolemia. We performed a screening phototest with a Dermaray Model M-DMR-1 (Eisai Co. Ltd., Tokyo) as light source (1, 2). This had a bank of 5 Toshiba FL 20S · E-30 fluorescent lamps for UVB on one side and a bank of 10 Toshiba FL 20S · BLB fluorescent lamps plus UV-33 glass filter (Toshiba Glass Co. Ltd., Tokyo) for UVA on the other. Output was measured with a standardized meter, Toshiba Model UVR-305/ 365. The intensity at the skin surface was 1 mW/cm2 at 305 nm for S · E-30 lamps and 7.5 mW/cm2 at 365 nm for BLB lamps. From the data of 78 normal subjects in our laboratory, the mean±SD of UVB-MED (minimal erythema dose) is 51.2± 13.2 mJ/cm2 and UVA-MED greater than 13.5 J/cm2• UVB-MED for this patient was normal (60 mJ/cm2), while 6.75 J/cm2 of UVA-irradiation, which was less than 1/ 2 of the UVA-MED in normal subjects, produced reddish papules on the irradiated area at 24 h, followed by erythema at 6 days after irradiation. Histological findings of the papular lesion at 24 h after 11.25 J/cm2 irradiation of UVA in the screening phototest demonstrated intraand intercellular edema in a hair follicle, slight hydropic degeneration of the basal layer near an acrosyringium, and lymphohistiocytic infiltration around a hair follicle and an eccrine duct. A screening phototest was performed again 4 weeks after she stopped taking simvastatin. Irradiation of 13.5 J/cm for UVA provoked no response, suggesting that photosensitivity to UVA of the patient had become normal. Patch and photopatch tests were performed with simvastatin (10, 1, and 0.1% pet.) and 6 standard photosensitizers (1 and 0.1% pet.). Only simvastatin 10% pet. with UVA irradiation (4.5 J/cm2) on photopatch testing showed papules at 24 h, followed by erythema at 6 days after irradiation. We did patch and photopatch tests in 5 normal subjects, and an oral challenge test with simvastatin in 6 normal subjects. None showed any erythema or papular response at 48 h, 6 days, or 8 days after application, or at 24 h or 6 days after irradiation.