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Actinic Prurigo

  • Author: Juan Pablo Castanedo-Cazares, MD, MSc; Chief Editor: Dirk M Elston, MD  more...
Updated: Oct 07, 2015


Actinic prurigo (AP) is a chronic, pruritic skin disease caused by an abnormal reaction to sunlight. In 1954, Escalona first described it in Mexico.[1] Lesions appear hours or days following sun exposure, contrary to what happens in solar urticaria, in which skin lesions appear minutes after UV exposure. It is commonly associated with cheilitis and conjunctivitis.[2, 3] See the images below.

Itchy plaques mainly on photoexposed areas of the Itchy plaques mainly on photoexposed areas of the face; these plaques are characteristic of actinic prurigo.
About 75% of patients have cheilitis, which can ta About 75% of patients have cheilitis, which can take the form of solid lesions or erosions.
One half of patients have bilateral conjunctivitis One half of patients have bilateral conjunctivitis. Eye protection is needed to avoid disease progression.


No systemic or local photosensitizer is known in patients with actinic prurigo, and a hypersensitivity implicating immunoglobulin E (IgE) has not been demonstrated.

Actinic prurigo has many features of a type IV hypersensitivity reaction. Skin lesions associated with actinic prurigo are infiltrated with T lymphocytes, mostly CD4+, and some of the T-cells express activation markers.[4] Actinic prurigo falls in the category of autoimmune diseases because lymphocytes from patients have been proven to be stimulated in a thymidine incorporation assay when confronted with their own UV-irradiated keratinocytes or UV-irradiated epidermal homogenates.[5]

At this point, the antigen that provokes the inflammatory reaction is not clear, but an epidermal protein is believed to be transformed by UV exposure. In the series by Santos-Martinez et al,[6] the presence of transforming growth factor-beta interleukin 13, and interleukin 10 was demonstrated in a non–type-TH1, non–type-TH2 pattern, similar to what has been shown in lesions of psoriasis and in the synovial fluid of rheumatoid arthritis.

Another potentially important finding in the pathogenesis of actinic prurigo may be the fact that Langerhans cells in persons with actinic prurigo show resistance to UV exposure when compared with those in healthy individuals.[7] This same finding has been shown in patients with a similar disease, polymorphous light eruption (PLE). Because these cells are resistant to their demise after UV exposure, they might handle and deliver UV-modified cutaneous antigens to T cells in larger amounts or in a more persistent way; this process could cause or augment the inflammatory phenomenon that is observed in the skin of patients with actinic prurigo. The apoptotic mechanism in these cells may be somewhat altered, facilitating their survival.

On the other hand, the polyclonal cellular immune response found in biopsy samples from Mexican patients through Southern blot analysis may involve an imbalance linked to a specific hyperimmunity, in which the proportion of autoimmune cells is increased and the proportion of other cells is decreased.[8]

Although different series are searching for a specific HLA, studies have shown associations with B40 and CW3 alleles in some populations, especially Amerindians.[9, 10] For instance, in the Chimila Indians from Colombia,[11] a high frequency of HLA-Cw4 was found. However, in Cree Indians from Saskatchewan, Canada,[12] the most common antigens were HLA-A24 and HLA-Cw4.

Other studies have shown a strong association with HLA-DR4. The more precise finding appears to be in the Mexican series, in which HLA-DR4 DRB1*0407 is found in more than 90% of patients with actinic prurigo.[13] Another series also found HLA-DR4 DRB1*0407 in Colombian patients.[14] Related alleles such as DRB*0407 have been found in British populations,[15] and DRB1*14 has been found in the Inuit Indians of Canada.[9]

Additional to the role of HLA-DR4 DRB1*0407 in the genetic susceptibility to develop actinic prurigo, HLA-DRB1*1406 could also be involved, and HLA-DRB1*0802 may possibly have a protective role. The existence of an HLA-B39-DRB1*0407 haplotype suggests a susceptibility region within the sixth human chromosome, at least among Amerindians affected by actinic prurigo.[16]

English patients with PLE[17] have not shown an association with any HLA, which suggests that HLA-DR4 (DRB1*0407) could be used as a marker to distinguish PLE from actinic prurigo. Therefore, the association with HLA in actinic prurigo but not in PLE suggests that actinic prurigo represents an immunologically mediated disease with strong genetic determinants for its expression.[11, 13]




United States

Actinic prurigo occurs in persons of all skin types, but its prevalence in the general population is unknown. It probably represents less than 5% of referrals to photodermatologic clinics.[18] Actinic prurigo is well known in the United States among Native Americans.[10, 11, 18, 19]


In Mexico, actinic prurigo represents 1.34% of consultations with pediatric dermatologists and 4% of consultations with general dermatologists.[1] Actinic prurigo is common in Mexico, Central America, and South America, and it is well known in Canada among Native Americans.[10, 11, 19] Actinic prurigo rarely occurs in Europe and Asia, where PLE (a disease with pathogenetic features similar to actinic prurigo) is more regularly seen. Isolated cases have been reported in France,[20] Germany,[21] Japan,[22] Singapore,[23] Thailand,[24] and Australia.[25] However, the prevalence rate of actinic prurigo in photodermatology clinics around the world varies from 0-5%.[23]


Actinic prurigo frequently affects admixture populations (eg, mestizos) of Latin America and American Indians with skin phototypes IV or V.


In children and adolescents, no differences in prevalence exist between the sexes. However, in adults, women are more frequently affected than men, with a female-to-male ratio of 2:1.[1, 18]


Actinic prurigo can occur at any age; however, one third of patients are children.[1] The impact on quality of life in this population is serious. By means of the children's dermatology life quality index (CDLQI), children with actinic prurigo show high scores and closer to those obtained in children with xeroderma pigmentosum.[26]

Contributor Information and Disclosures

Juan Pablo Castanedo-Cazares, MD, MSc Photobiology Unit Director, Assistant Professor, Department of Dermatology, Hospital Central, Universidad Autonoma de San Luis Potosi, Mexico

Juan Pablo Castanedo-Cazares, MD, MSc is a member of the following medical societies: Photomedicine Society, Mexican National Research Association

Disclosure: Nothing to disclose.


Bertha Torres-Alvarez, MD Assistant Professor of Dermatology, Hospital Central, Universidad Autonoma de San Luis Potosi

Disclosure: Nothing to disclose.

Specialty Editor Board

David F Butler, MD Section Chief of Dermatology, Central Texas Veterans Healthcare System; Professor of Dermatology, Texas A&M University College of Medicine; Founding Chair, Department of Dermatology, Scott and White Clinic

David F Butler, MD is a member of the following medical societies: American Medical Association, Alpha Omega Alpha, Association of Military Dermatologists, American Academy of Dermatology, American Society for Dermatologic Surgery, American Society for MOHS Surgery, Phi Beta Kappa

Disclosure: Nothing to disclose.

Lester F Libow, MD Dermatopathologist, South Texas Dermatopathology Laboratory

Lester F Libow, MD is a member of the following medical societies: American Academy of Dermatology, American Society of Dermatopathology, Texas Medical Association

Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD Professor and Chairman, Department of Dermatology and Dermatologic Surgery, Medical University of South Carolina College of Medicine

Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology

Disclosure: Nothing to disclose.

Additional Contributors

Craig A Elmets, MD Professor and Chair, Department of Dermatology, Director, Chemoprevention Program Director, Comprehensive Cancer Center, UAB Skin Diseases Research Center, University of Alabama at Birmingham School of Medicine

Craig A Elmets, MD is a member of the following medical societies: American Academy of Dermatology, American Association of Immunologists, American College of Physicians, American Federation for Medical Research, Society for Investigative Dermatology

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: University of Alabama at Birmingham; University of Alabama Health Services Foundation<br/>Serve(d) as a speaker or a member of a speakers bureau for: Ferndale Laboratories<br/>Received research grant from: NIH, Veterans Administration, California Grape Assn<br/>Received consulting fee from Astellas for review panel membership; Received salary from Massachusetts Medical Society for employment; Received salary from UpToDate for employment. for: Astellas.


The authors and editors of Medscape Reference gratefully acknowledge the contributions of previous authors, Veronica Lepe Murillo, MD, and Benjamin Moncada, MD, to the development and writing of this article.

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Itchy plaques mainly on photoexposed areas of the face; these plaques are characteristic of actinic prurigo.
Photodistribution of lesions over the body. Note the hypopigmented areas of the skin, which are very common after intense scratching in children.
Multiple itchy papules coalescing into plaques on the neck. These lesions are similar to lesions of polymorphous light eruption. Note the excoriations induced by scratching.
One third of patients are children. The nose is frequently affected. This clinical feature is useful in distinguishing it from other entities, such as atopic dermatitis.
One half of patients have bilateral conjunctivitis. Eye protection is needed to avoid disease progression.
About 75% of patients have cheilitis, which can take the form of solid lesions or erosions.
A phototest with UV-B light shows reproduction of lesions on the inner aspect of the arm. The result from the phototest with UV-A light was negative.
Histologic examination shows acanthosis, mild spongiosis, edema of the lamina propria, and a moderate-to-dense perivascular lymphocytic inflammatory infiltrate.
A close-up view shows edema of the lamina propria as well as a lymphocytic inflammatory infiltrate in the dermis.
Young girl with a history of atopic dermatitis and itchy, lichenified plaques on her face for the last 3 months. Atopic dermatitis with photosensitivity is the main differential diagnosis with actinic prurigo in children.
Actinic cheilitis resulting from actinic prurigo.
Erythematous and very itchy plaques on solar exposure areas of the face and pseudopterygium are commonly observed in actinic prurigo.
Lichenified plaques, excoriated nodules, and atrophic scars on the dorsal aspect of hands are frequently seen in children.
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