Psoralen and ultraviolet A therapy

Psoralen and Ultraviolet A Therapy

Psoralen and Ultraviolet A (PUVA) therapy is a type of photochemotherapy used primarily in the treatment of various skin disorders, including psoriasis, vitiligo, and cutaneous T-cell lymphoma. This therapy combines the administration of a photosensitizing agent, psoralen, with exposure to ultraviolet A (UVA) light.

Mechanism of Action

PUVA therapy works by utilizing the properties of psoralen, a compound that sensitizes the skin to UVA light. Psoralen can be administered orally or topically. Once psoralen is absorbed into the skin, the patient is exposed to UVA light, which penetrates the skin and interacts with the psoralen. This interaction causes changes in the DNA of skin cells, leading to a therapeutic effect.

The primary mechanism involves the formation of cross-links between DNA strands, which inhibits cell proliferation and induces apoptosis in hyperproliferative skin cells. This is particularly beneficial in conditions like psoriasis, where there is excessive growth of skin cells.

Indications

PUVA therapy is indicated for several dermatological conditions:

• Psoriasis: Particularly effective in chronic plaque psoriasis, PUVA can help reduce the scaling, thickness, and redness of psoriatic plaques.
• Vitiligo: PUVA can stimulate repigmentation in vitiligo by inducing melanocyte proliferation and migration.
• Cutaneous T-cell Lymphoma: PUVA is used to treat early-stage mycosis fungoides, a type of cutaneous T-cell lymphoma.
• Eczema: In some cases, PUVA is used to manage severe eczema that does not respond to other treatments.

Procedure

The PUVA treatment process involves several steps:

1. Psoralen Administration: Psoralen can be taken orally in pill form or applied topically as a lotion or bath. 2. UVA Exposure: After a specified time to allow psoralen absorption, the patient is exposed to UVA light in a special chamber. The duration and intensity of exposure are carefully controlled. 3. Post-Treatment Care: Patients are advised to protect their skin from sunlight for at least 24 hours after treatment to prevent burns and other side effects.

Side Effects

Common side effects of PUVA therapy include:

• Nausea: Often associated with oral psoralen.
• Erythema: Redness of the skin similar to sunburn.
• Pruritus: Itching of the skin.
• Increased Risk of Skin Cancer: Long-term PUVA therapy can increase the risk of squamous cell carcinoma and, to a lesser extent, melanoma.

Contraindications

PUVA therapy is contraindicated in patients with:

• Photosensitivity Disorders: Such as lupus erythematosus.
• History of Skin Cancer: Due to the increased risk of carcinogenesis.
• Pregnancy: Due to potential risks to the fetus.

Also see

• Phototherapy
• Psoriasis
• Vitiligo
• Cutaneous T-cell lymphoma
• Ultraviolet light