Written by: Lucky Annem
Medically reviewed by: Dr. Lohi Pratti
Actinic prurigo (AP) is a rare photodermatosis, characterized by an inherited sensitivity to UV radiation that results in persistent itching and the development of papules, plaques, and nodules on sun-exposed skin. AP mainly affects individuals of Native American or Latin American descent, but cases have been reported worldwide. The condition is also known as hereditary polymorphic light eruption, familial polymorphic light eruption, or Hutchinson's summer prurigo. In this research paper, we will discuss the etiology, clinical manifestations, diagnosis, and treatment of AP.
Causes
The exact cause of actinic prurigo is not yet known, but it is believed to be a combination of genetic and environmental factors. Studies have shown that there is a strong genetic component to the disease, as it tends to run in families. Environmental factors, such as exposure to sunlight and other UV radiation, are also thought to play a role in the development of actinic prurigo. According to certain research, actinic prurigo may be more common in specific regions with dry, warm temperatures that are at least 1000 meters above sea level. The condition is more common in people who live in areas with high levels of UV radiation, such as in high-altitude regions or near the equator. Other potential risk factors include a history of sunburns or other skin damage, as well as certain medications, such as tetracyclines or phenothiazines. The immune system is also thought to play a role in the development of actinic prurigo. The condition is considered to be an autoimmune disorder, meaning that the immune system mistakenly attacks the body's own cells and tissues. In the case of actinic prurigo, the immune system targets cells in the skin that have been damaged by UV radiation. This leads to inflammation and itching, which can be severe in some cases. The exact mechanisms behind this immune response are still not fully understood, but it is believed to involve a complex interplay between different cells and signaling molecules in the body.
Clinical manifestations
Actinic prurigo can happen to anybody of any age or gender, however, it is commonly characterized in prepubescent girls with mean onset before age 10. The clinical presentation of AP is variable, but most patients present with itching and erythema on sun-exposed areas, such as the face, neck, and upper limbs. The itching can be severe and may interfere with daily activities. Patients with actinic prurigo are known to exhibit actinic cheilitis as a hallmark
Feature. Skin lesions develop after repeated exposure to sunlight and may take several months or years to appear. The lesions are typically papular, erythematous, and scaly, and may progress to form plaques or nodules. In severe cases, the lesions may become ulcerated or secondarily infected. AP may also affect the lips and oral mucosa, causing painful erosions or ulcers. On the lips, a type of precancerous lesion that is a hallmark feature of actinic prurigo called actinic cheilitis may occur.
Diagnosis
The diagnosis of AP is based on the clinical presentation and a history of sun exposure. A skin biopsy may be necessary to rule out other skin conditions, such as lupus erythematosus or cutaneous T-cell lymphoma. Photo testing may also be performed to confirm the diagnosis and determine the patient's sensitivity to UV radiation.
Treatment
Systemic treatments, which are taken orally, are also available for severe cases. These include antimalarial drugs like hydroxychloroquine and chloroquine, which have been found to be effective in reducing symptoms in some patients. Immunosuppressive drugs like cyclosporine have also been used in severe cases, but require close monitoring due to potential side effects. Phototherapy is another treatment option for actinic prurigo. Narrowband ultraviolet B (NB-UVB) therapy has been found to be effective in reducing symptoms, with some studies showing complete remission in some patients. PUVA therapy, which involves taking a medication called psoralen followed by exposure to UVA light, has also been used but has some potential side effects. Mild actinic prurigo can be treated with sun protection and avoidance: remaining indoors or in covered places, wearing protective clothing, sunglasses, wide-brim hats, and broad-spectrum SPF. Additionally, topical corticosteroids and non-sedating antihistamines help in acute episodes.
Image Source: Dermatologic Clinics
References:
“Actinic Prurigo | DermNet.” Dermnetnz.org, 2022, dermnetnz.org/topics/actinic-prurigo.
“Andrews’ Diseases of the Skin : Clinical Dermatology | WorldCat.org.” Worldcat.org, 2023, www.worldcat.org/title/andrews-diseases-of-the-skin-clinical-dermatology/oclc/62736861.
Pablo, Juan. “Actinic Prurigo Treatment & Management: Medical Care, Prevention.” Medscape.com, Medscape, 18 Apr. 2022, emedicine.medscape.com/article/1120153-treatment.
Pile, Hannah D., and Jonathan S. Crane. “Actinic Prurigo.” Nih.gov, StatPearls Publishing, 8 May 2022, www.ncbi.nlm.nih.gov/books/NBK499957/.
Rustin, Malcolm H. A. “Andrews’ Diseases of the Skin - Clinical Dermatology.” Postgraduate Medical Journal, vol. 66, no. 781, 1990, p. 984, www.ncbi.nlm.nih.gov/pmc/articles/PMC2429767/.
Wiseman, Marni C., et al. “Actinic Prurigo: Clinical Features and HLA Associations in a Canadian Inuit Population.” Journal of the American Academy of Dermatology, vol. 44, no. 6, June 2001, pp. 952–56, https://doi.org/10.1067/mjd.2001.112579.
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