Failure of physiologic doses of pure UVA or UVB to induce lesions in photosensitive cutaneous lupus erythematosus: implications for phototesting

BACKGROUND: Phototesting studies in cutaneous lupus erythematosus have yielded variable results, with most trials reporting photo-induction of lesions by both UVA and UVB in substantial numbers of patients. OBJECTIVES: To determine the minimal erythema dose in patients with subacute cutaneous lupus erythematosus (SCLE) and controls. PATIENTS/METHODS: We phototested nine patients with SCLE and 14 skin type-matched controls, using repetitive dosing of UVA1 and UVB, but with filters that removed most of the shorter UVC and longer infrared and visible light. In addition, DNA was isolated from anticoagulated blood to genotype the TNF-alpha 308 region in each patient and control. RESULTS: We were unable to demonstrate a difference in minimal erythema dose (MED) between patients and controls, or any correlation of MED with either TNF genotype or systemic drug therapy for SCLE. In addition, no SCLE skin lesions were induced in the nine patients with either UVA or UVB, and one patient cleared a skin lesion after low-dose UVA1 irradiation. CONCLUSIONS: The potential role of wavelengths outside the UVA and UVB range in the photo-induction of cutaneous lupus skin lesions needs to be investigated, and there is a need to standardize phototesting equipment and procedures for patients with cutaneous lupus erythematous.