PUVA therapy

PUVA therapy
Intervention
MeSH D011701

PUVA is an ultraviolet light therapy treatment for eczema, psoriasis, graft-versus-host disease, vitiligo, mycosis fungoides, large-plaque parapsoriasis and cutaneous T-cell lymphoma using the sensitizing effects of the drug psoralen.[1]:686[2][3] The psoralen is applied or taken orally to sensitize the skin, then the skin is exposed to UVA.

Photodynamic therapy is the general use of nontoxic light-sensitive compounds that are exposed selectively to light, whereupon they become toxic to targeted malignant and other diseased cells. Still, PUVA therapy is often classified as a separate technique from photodynamic therapy.[4][5]

Procedure

Psoralens are materials that make the skin more sensitive to UV light. They are called photosensitizing agents and they found in plants or manufactured artificially. Psoralens are taken as pills ( systemically) or can be applied directly to the skin, by soaking the skin in a solution that contains psoralen. The psoralens allow to lower the dose of the UVA energy. When they are combined with exposure to UVA in PUVA, they are highly effective at clearing psoriasis and vitiligo. Like UVB light treatments, the reason in case of vitiligo is that they increase the sensitivity of the Melanocyte, the cell that manufactures the skin color, to UV light. The melanocyte has sensors that see the UV light and tells it to manufacture the skin brown color. The color protects the body from the harming UV light. It can also be a connection with the skin's immune response.

The physician can choose a starting dose based on the patient's skin type. The dose will increase in every treatment until the skin starts to respond, normally when it becomes a little bit pink.

Some clinics test the skin before the treatments, by exposing a small area of the patient's skin to UVA, after ingestion of psoralen. The dose of UVA that produces uniform redness 12 hours later, called the minimum phototoxic dose (MPD), or minimal erythema dose (MED) becomes the starting dose for treatment.

At the very least for vitiligo, narrowband ultraviolet B (UVB) phototherapy is now used more commonly than PUVA since it does not require the use of the psoralen. As with PUVA, treatment is carried out twice weekly in a clinic or every day at home, and there is no need to use psoralen.[6]

Narrowband UVB is less effective for the legs and hands, compared to the face and neck. To the hands and legs PUVA may be more effective. The reason can be because UVA penetrates deeper in the skin, and the melanocytes in the skin of the hands and legs is deeper in the skin. The Narrowband UVB does not reach the melanocytes.

Side effects and complications

Some patients experience nausea and itching after ingesting the psoralen compound. For these patients PUVA bath therapy may be a good option.

Long term use of PUVA therapy has been associated with higher rates of skin cancer.[7]

The most significant complication of PUVA therapy for psoriasis is squamous cell skin cancer. Two carcinogenic components of the therapy include the nonionizing radiation of UVA light as well as the psoralen intercalation with DNA. Both processes negatively contribute to genome instability.

History

Psoralens have been known at least since ancient Egypt. In the 1890s Niels Ryberg Finsen of Copenhagen developed a bulky phototherapy machine to treat skin diseases using UV light. In 1900, French electrical engineer, Gustave Trouvé miniaturized Finsen’s machine with a series of portable light radiators to heal skin diseases such as lupus and epithelioma. Such machines have only been available in a chemically synthesized form since the 1970s.[8]

See also

References

  1. ↑ James, William D.; Berger, Timothy G.; et al. (2006). Andrews' Diseases of the Skin: clinical Dermatology. Saunders Elsevier. ISBN 0-7216-2921-0.
  2. ↑ Domínguez MA, Membrillo VG, Ramos GA (2004). "Large plaque parapsoriasis and PUVA-therapy. A case report".
  3. ↑ MacMillan Cancer Support Group. "Cutaneous T-cell lymphoma (CTCL)".
  4. ↑ Finlan, L. E.; Kernohan, N. M.; Thomson, G.; Beattie, P. E.; Hupp, T. R.; Ibbotson, S. H. (2005). "Differential effects of 5-aminolaevulinic acid photodynamic therapy and psoralen + ultraviolet a therapy on p53 phosphorylation in normal human skin in vivo". British Journal of Dermatology. 153 (5): 1001–10. doi:10.1111/j.1365-2133.2005.06922.x. PMID 16225614.
  5. ↑ Champva Policy Manual, Chapter: 2, Section: 30.11, Title: PDT (Photodynamic Therapy) and PUVA (Photochemotherapy) at U.S. Department of Veterans Affairs. Date: 12/23/2011
  6. ↑ What are the treatment options for vitiligo?
  7. ↑ Melissa Conrad Stöppler, MD. "Psoriasis PUVA Treatment Can Increase Melanoma Risk".
  8. ↑ Gustave Trouvé French Electrical Genius (1839–1902)" - McFarland Books – Author: Kevin Desmond pp. 162–-164
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