Phototherapy: UVB, PUVA, and Excimer Laser Protocols

Overview / Definition Phototherapy involves the use of specific wavelengths of light to treat skin disorders. The primary types include Ultraviolet B (UVB), Psoralen and Ultraviolet A (PUVA), and Excimer Laser. These therapies are particularly effective in managing inflammatory skin conditions, including but not limited to psoriasis, atopic dermatitis, and vitiligo. Epidemiology Phototherapy is widely utilized in the treatment of chronic skin diseases. The prevalence of conditions treated with phototherapy varies: Approximately 2% of the population is affected by psoriasis. Atopic dermatitis affects up to 20% of children and 1-3% of adults. Vitiligo has a prevalence of about 1% globally. Pathophysiology / Mechanism The mechanisms of action for phototherapy vary by type: UVB: Inhibits keratinocyte proliferation and promotes apoptosis of activated T-cells. PUVA: Combines UVA with psoralen to enhance skin absorption of light, leading to a more profound immunosuppressive effect. Excimer Laser: Delivers targeted UVB light to specific lesions, minimizing damage to surrounding healthy tissue. Clinical Presentation Conditions commonly treated with phototherapy present as follows: Psoriasis: Well-defined erythematous plaques with silvery scales. Atopic Dermatitis: Pruritic, eczematous lesions often in flexural areas. Vitiligo: Depigmented patches on the skin. Diagnosis / Workup The diagnosis of conditions warranting phototherapy typically involves: Clinical evaluation and history-taking. Consideration of skin biopsy for atypical cases. Assessment of patient's skin type and previous treatment history. Treatment / Management Management protocols differ for each phototherapy type: UVB Therapy Initial sessions: 2-3 times weekly. Duration: 15-30 minutes based on skin type and disease severity. Monitor for erythema and adjust exposure time accordingly. PUVA Therapy Administer psoralen 1-2 hours before UVA exposure. Sessions typically twice weekly. Monitor for phototoxic reactions