Solar Urticaria

Also known as SU, it is a rare and severe disorder occurring in less than 1% of the population. Following limited exposure to sunlight, sufferers may develop an itchy or burning redness on exposed skin. More prolonged exposure can result in the development of "wheals" or round red raised areas on the skin. These symptoms can also be accompanied by headache, nausea, breathing difficulty or fainting. The symptoms usually develop soon after sun exposure and last anywhere from 30 minutes to 24 hours.

Treatment is usually directed towards relief of symptoms. Most commonly, antihistamines with or without systemic steroids are used. Desensitisation with UV light sources has been used but this carries the risk of provoking symptoms. Immunosuppressants such as cyclosporin and intravenous immunoglobulins have also been used.

In extreme cases these patients need to be hospitalised to undergo plasmaphoresis (a procedure similar to dialysis where the plasma in their blood is removed and the blood cells are returned to the patient).

With the use of afamelanotide it is hoped that in at risk patients the incidence and/or severity of attacks of solar urticaria will be significantly reduced.

Clinuvel released results from a Phase II trial in July 2009 (view the company's announcement). The company aims to commence a Phase III trial of SU in Europe in 2010

Afamelanotide has been granted Orphan Drug Designation by the EMA, FDA and Swissmedic for SU.

For more information on SU, please see the Clinuvel Photoprotection SU page.

References

Dice JP. "Physical Urticaria", Immunol Allergy Clin N Am 2004;24:225-46
Ng JHC, Foley PA, Crouch RB, Baker CS. "Changes of Photosensitivity and Action Spectrum with Time in Solar Urticaria". Photodermatol Photoimmunol Photomed 2002;18:191-95
Roelandts R. "Diagnosis and Treatment of Solar Urticaria", Dermatologic Therapy 2003;16:52-56