Actinic Prurigo

Article Author:
Hannah Pile
Article Editor:
Jonathan Crane
Updated:
12/5/2018 10:06:47 AM
PubMed Link:
Actinic Prurigo

Introduction

Actinic prurigo (AP) is a rare form of an idiopathic photodermatosis that primarily affects sun-exposed areas of the skin. The affected regions of the skin typically include the face, neck, and dorsal surface of the upper extremities. Sun protected areas of the skin such as the buttocks have also been described. Actinic prurigo typically manifests in the spring as a symmetric intensely pruritic papulonodular dermatitis and can persist into the winter months. In severe cases, excoriations, cheilitis, conjunctival disease, and scarring may develop. Actinic prurigo is typically described in prepubescent females but can occur at any age or gender. The disease has a strong genetic component and is more commonly seen in American Indians of North, Central, and South America. Diagnosis is mainly clinical. Disease management begins with sun protection and sunlight avoidance. Treatment involves topical antihistamines and steroids,  photochemotherapy (PUVA), and systemic therapies for severe cases. Without treatment, this disease course remains chronic and can persist into adulthood.[1][2][3]

Etiology

The etiology remains unclear, but there is a strong genetic component suggesting an autoimmune basis for actinic prurigo. The human leukocyte antigen DR4 allele variant is present in 90% of cases, especially the DR4 subtype DRB1*0407 which is seen in 60% of cases.[4]

Epidemiology

Actinic prurigo is a rare photodermatosis in the United States. However, actinic prurigo is more common in the American Indian populations of North, Central, and South America. The disease can affect both genders but is more commonly described in female patients. Actinic prurigo can manifest at any age, although the disease typically presents in prepubescent individuals with the mean onset before age 10. Some studies suggest an increased prevalence of actinic prurigo in certain geographic areas with dry, warm climates at an altitude of at least 1000 meters above sea level.[5][6][7]

Pathophysiology

The pathophysiology of actinic prurigo remains largely unclear, but evidence suggests the disease process is driven by a delayed type-IV hypersensitive response to ultraviolet A and B (UVA and UVB) radiation in genetically predisposed individuals. Both TH1 and TH2 lymphocytic processes have been implicated in the disease process. Multiple studies note the presence of eosinophils and mast cells in the dermal layers of involved tissue which suggests a type-IVb (TH2)-driven response specifically. TH2 lymphocytes secrete IL-4, IL-5, and IL-13 which promote IgE and IgG4 production by B cells. These immunoglobulins stimulate eosinophils and mast cells. Individuals with moderate to severe actinic prurigo have been found to have markedly elevated IgE levels, further supporting a type-IVb (TH2) hypersensitive reaction.[8]

Histopathology

Biopsy alone is not sufficient to make a diagnosis of actinic prurigo, but histopathology can be helpful in aiding diagnosis and excluding other disease processes with similar presentations. Skin biopsies will show hyperkeratosis, spongiosis, and acanthosis in the epidermis with lymphocytic perivascular infiltration in the dermis. A lip biopsy will show the presence of lymphoid germinal centers in the lamina propria, which can help distinguish actinic prurigo from the polymorphous light eruption. Studies have also described an infiltration of eosinophils and mast cells in the underlying mucosa of affected lesions which correlate with a delayed type-IVb hypersensitive response.

History and Physical

Patients with actinic prurigo will typically present in early spring as sunlight becomes more prevalent and individuals spend more time exposing their skin to sunlight outdoors. Patients will present with intensely itchy, erythematous papulonodular lesions on predominantly sun-exposed areas of the skin. The face, especially over the zygomatic arches, nasal bridge, lower lip, and conjunctiva, is typically affected; although, lesions may develop anywhere on the neck, trunk, extremities, and even non-sun exposed areas such as the buttocks. Since the lesions are intensely pruritic, excoriations, skin thickening, scarring, and hyper- or hypopigmentation may occur.

Actinic cheilitis has been described as a hallmark finding in patients with actinic prurigo. Individuals may present with actinic cheilitis as a solitary finding or in concurrence with more widespread papulonodular lesions.

Evaluation

Actinic prurigo is typically diagnosed clinically with a detailed history and physical exam. Patients will report the characteristic symptoms of severely pruritic papulonodular erythematous skin lesions that began in the spring or summer months. Patients may or may not report a direct correlation with exposure to sunlight and disease onset. Diagnosis can be aided by skin photo testing, histologic evaluation, and genetic screening for the HLA DR4 allele variant. Laboratory testing and immunofluorescence studies are often performed to rule out lupus erythematosus and other photosensitive dermatoses.[8]

Treatment / Management

Minor cases of actinic prurigo can be treated with sun-avoidance alone. Proper sun protection includes avoiding sunlight by staying indoors or in shaded areas, wearing protective clothing, sunglasses, and wide brim hats, and using a broad-spectrum sunscreen. Topical steroids and non-sedating antihistamines will provide relief for acute episodes. The more severe and persistent disease requires treatment with systemic therapies such as antimalarials, tetracyclines, and systemic steroids.

Thalidomide has been described as the hallmark therapy for severe refractory cases of actinic prurigo. Treatment with thalidomide has a major limiting side effect profile which includes peripheral neuropathy and teratogenicity. Treatment with thalidomide is contraindicated during pregnancy or in individuals trying to become pregnant. Females of childbearing age must use contraception during therapy with thalidomide. Screening for peripheral neuropathy is typically initiated pre-treatment and continued throughout the treatment process.

Alternative immunosuppressive regimens with agents like cyclosporine A have been described as successful as well. Photochemotherapy with psoralen and ultraviolet A (PUVA) has also been shown to be successful in managing symptoms and treating skin changes caused by actinic prurigo.[9][10]

Differential Diagnosis

Originally, actinic prurigo was thought to be a hereditary type of polymorphous light eruption (PMLE), a more common idiopathic photodermatoses. Genetic testing and the unique clinical presentation of actinic prurigo now supports two separate disease entities. The HLA-DR4 allele, specifically the DRB1*0407 subtype is strongly associated with actinic prurigo and not PMLE. Actinic prurigo also has an earlier age of onset and frequently presents with cheilitis and sometimes conjunctivitis, which is never seen in patients with PMLE. When suspecting actinic prurigo, laboratory tests should also be performed to rule out systemic diseases such as lupus erythematosus or porphyria.

Prognosis

Actinic prurigo is a chronic disease process and can reoccur with repeated sun exposure. Treatment with immunosuppressive agents like thalidomide and cyclosporine A have been shown to be effective at long-term suppression of symptoms. Some adolescents may have spontaneous resolution of symptoms and may not have disease progression into adulthood.

Complications

  • Secondary bacterial infections
  • Contact dermatitis
  • Impetigo

Enhancing Healthcare Team Outcomes

Actinic prurigo does not resolve with time and is marked by frequent relapses. Hence the role of the pharmacist and nurse are critical. All patients must be told to avoid sun exposure. Even going out during the day can cause a relapse of the condition within minutes. Thus, the patient should be educated by the clinician, nurse or pharmacist about wearing long dark sleeved garments, a hat, and sunglasses. No part of the skin should be exposed to the sun and participation in outdoor sports is not recommended. The use of sunscreens is not recommended as they contain chemicals that can exacerbate the skin lesions. Only mineral sunscreens can be used. To avoid exacerbations, the sunscreen must also be applied properly. Before going out, the patient must be aware of the UV index and weather. This skin condition is very labile and even minor exposure to the sun can lead to an outbreak.[11][12] (Level III)

Outcomes

For most patients with actinic prurigo, the outcomes are poor. The condition is associated with frequent relapses, especially during the warmer months of the year. The condition rarely spontaneously resolves and is chronic. The overall quality of life is poor.[13][14] (Level III)


References

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[2] Sitek JC, Actinic Prurigo in Scandinavian Adolescent Successfully Treated with Cyclosporine A. Dermatology reports. 2017 Mar 13     [PubMed PMID: 29142659]
[3] Oakley AM,Badri T, Photosensitivity null. 2018 Jan     [PubMed PMID: 28613726]
[4] Vega Memije ME,Cuevas Gonzalez JC,Hojyo-Tomoka MT,Rodríguez Lobato E, Actinic prurigo as a hypersensitivity reaction type 4. International journal of dermatology. 2017 Jun     [PubMed PMID: 28239837]
[5] Naka F,Shwayder TA,Santoro FA, Photodermatoses: Kids are not just little people. Clinics in dermatology. 2016 Nov - Dec     [PubMed PMID: 27968932]
[6] Chen YA,Yang CC,Ting SW,Lee JY,Chen W, Adult-onset actinic prurigo: report of 19 patients from Taiwan. Journal of the European Academy of Dermatology and Venereology : JEADV. 2016 Nov     [PubMed PMID: 26538497]
[7] Rodríguez-Carreón AA,Rodríguez-Lobato E,Rodríguez-Gutiérrez G,Cuevas-González JC,Mancheno-Valencia A,Solís-Arias MP,Vega-Memije ME,Hojyo-Tomoka MT,Domínguez-Soto L, Actinic Prurigo. Skinmed. 2015 Jul-Aug     [PubMed PMID: 26861426]
[8] Cuevas-Gonzalez JC,Lievanos-Estrada Z,Vega-Memije ME,Hojyo-Tomoka MT,Dominguez-Soto L, Correlation of serum IgE levels and clinical manifestations in patients with actinic prurigo. Anais brasileiros de dermatologia. 2016 Jan-Feb     [PubMed PMID: 26982774]
[9] Plaza JA,Toussaint S,Prieto VG,Mercadillo P,Diez de Medina JC,Lourenco S,Batdorf B,Sangueza M, Actinic Prurigo Cheilitis: A Clinicopathologic Review of 75 Cases. The American Journal of dermatopathology. 2016 Jun     [PubMed PMID: 26981737]
[10] Jones AC,McGuff HS,Huber M, Oral and Maxillofacial Pathology. Case of the Month. Actinic prurigo. Texas dental journal. 2015 Mar     [PubMed PMID: 26234110]
[11] Gomes-Neto A,Aguilera P,Prieto L,Seité S,Moyal D,Carrera C,Malvehy J,Puig S, Efficacy of a Daily Protective Moisturizer with High UVB and UVA Photoprotection in Decreasing Ultraviolet Damage: Evaluation by Reflectance Confocal Microscopy. Acta dermato-venereologica. 2017 Nov 15     [PubMed PMID: 28661544]
[12] Millard TP,Hawk JL, Photosensitivity disorders: cause, effect and management. American journal of clinical dermatology. 2002     [PubMed PMID: 12010069]
[13] Macfarlane L,Hawkey S,Naasan H,Ibbotson S, Characteristics of actinic prurigo in Scotland: 24 cases seen between 2001 and 2015. The British journal of dermatology. 2016 Jun     [PubMed PMID: 26847497]
[14] Chen Q,Shen M,Heng YK,Theng TSC,Tey HL,Ren EC,Chong WS, Actinic Prurigo in Singaporean Chinese: A Positive Association with HLA-DRB1*03:01. Photochemistry and photobiology. 2016 Mar     [PubMed PMID: 26787110]