Clinical Characteristics of Photodermatoses in Indian Patients and their Phototesting Findings: A Cross-sectional Study

Introduction: Phototesting helps to confirm photosensitivity, identify the action spectra, reproduce lesions by photo provocation for biopsy, calculate starting dose of desensitisation therapy, assess the severity of the photodermatoses, and monitor response to treatment. The effect of sunlight on darker skin has only been sparingly studied and hence, this study was undertaken in our population. Aim: To identify the spectrum of photodermatoses, with their clinical characteristics and phototesting findings. Materials and Methods: A cross-sectional study was conducted in Outpatient Department (OPD) of the Department of Dermatology, Pushpagiri Medical College, Tiruvalla, Kerala, India from January to December 2015. A total of 30 patients clinically diagnosed as photodermatoses were subjected to phototesting using the whole body phototherapy unit with Ultraviolet A (UVA) and UVB exposure. After 24 hours the UV-exposed areas were examined for the Minimal Erythema Dose (MED), and for the reoccurrence of skin lesions to determine the action spectra for the disorder, and the values were expressed in mean, frequency, and percentage. Results: Polymorphic Light Eruption (PLE) remains the most common photodermatosis (n=25) with a definite female preponderance (n=19). The mean MED-UVB for type IV skin with photodermatoses was found to be 766 mj/cm2 and for type V skin was found to be 900 mj/cm2 . MED-UVA was not observed in the majority of patients (n=24). Among the 25 patients with PLE, 16 patients had normal MED values to both UVA and UVB, four had reduced MED-UVB alone, one patient to UVA alone, and three patients had reduced MED to both. MED-UVB was not observed in one patient. MED-UVA was not observed in 21 patients (normal). Of the three patients with photoallergic dermatitis, one patient had reduced MED-UVB and MED-UVA. The other two patients had normal MEDs. The chronic actinic dermatitis patient had reduced MED to UVB and UVA and the actinic lichen planus patient had normal MEDs. Conclusion: Phototesting remains a very useful tool in the evaluation and management of photodermatoses and PLE was the most common photodermatoses in studied population.