Diagnosis: Actinic Prurigo
Actinic prurigo is a rare, idiopathic chronic photodermatosis found in all skin types and age groups, but most commonly affecting Latin American Mestizo and Native American girls of skin phototypes IV and V.1 Among children and adolescents, there is no gender difference in prevalence. Among adults, females are more commonly affected than men, with a female-to-male ratio of 2:1.2
Epidemiology and Pathogenesis
The pathogenesis has not been clearly elucidated, but several studies have suggested that it is an immune-mediated condition.2,3 Skin lesions from patients with actinic prurigo demonstrate infiltration by T cells, most of which are CD4+.2 The antigen provoking this robust inflammatory response has not been found. Langerhans cells from patients with actinic prurigo show resistance to ultraviolet (UV) exposure when compared to those from unaffected individuals.4 This resistance to apoptosis may allow the Langerhans cells to present UV-modified antigens to T cells, eliciting the immune response that creates the clinical condition of actinic prurigo.
Clinical Presentation
The polymorphic clinical features of actinic prurigo include erythematous papules, nodules, crusts and lichenified plaques due to chronic scratching. The dermatitis is typically bilateral and symmetric. Cutaneous manifestations appear hours to days following exposure to both UVA and UVB on sun-exposed skin. In chronic disease, lesions may be found on sun-protected skin, as well. Though onset of symptoms typically occurs during the spring or summer months, they can persist during the winter.3 Approximately 65% of patients have cheilitis, which may be the only site of involvement in a 10% of patients.2 Eye involvement in the form of pseudopterygium, limbitis (inflammation of the limbus or border between the cornea and the sclera) and conjunctivitis is present in up to 45% of cases.2,5,6
Histopathology
Histologic examination shows hyperkeratosis, regular acanthosis, mild spongiosis, edema of the lamina propria and a dense lymphohistiocytic infiltrate that can have a band-like distribution, or occasionally form follicles.5,6 Follicles are more common in the mucosae, conjunctivae and the lips. Numerous eosinophils, basal cell layer vacuolization and dilation of dermal capillaries are typically present.3
Direct immunofluorescence studies are negative in actinic prurigo.2
Differential Diagnosis
Several conditions need to be considered in the differential diagnosis, including polymorphous light eruption, atopic dermatitis with photosensitivity (this is the major differential diagnosis in children),2 chronic actinic dermatitis, hydroa vacciniforme, discoid lupus erythematous and Jessner lymphocytic infiltrate.3
Management
Rigorous sun protection is the cornerstone of treatment. Of the pharmacologic therapies currently available, thalidomide 100 mg daily is considered the most effective.1,3 Thalidomide can be gradually tapered off, and restarted again when a patient has an exacerbation.
Topical steroids, emollients and oral antihistamines may relieve the pruritus associated with cutaneous lesions. Acute exacerbations can also be mitigated by a short course of oral corticosteroids.7 Unfortunately, antimalarials and immunosuppressants have proven only partially effective.1,3
Localized ocular symptoms such as conjunctivitis have been well-controlled with application of 2% cyclosporine A.8
Though actinic prurigo is not associated with increased mortality, it has deleterious effects on a patient’s quality of life because it can be disfiguring and it is difficult to achieve complete UV light protection.
Our Patient
Skin biopsy specimens were obtained from the conjunctiva (Figure 2A), nose (Figure 2B) and lower lip (Figure 2C). Tissue from the nasal biopsy was also sent for pan-culture.
Figure 2A. 4x. Hematoxylin and eosin stained biopsy specimen of the conjunctiva. Lymphoid infiltrate forming a large follicle.
Figure 2B.10x. Hematoxylin and eosin stained biopsy specimen of the nose. Focal spongiosis and nodular lymphoid infiltrate.
Figure 2C. 10x. Hematoxylin and eosin stained biopsy specimen of the lower lip. Mild acanthosis, prominent chronic inflammation with nodular lymphoid infiltrate.
Hematoxylin and eosin staining of specimens from the conjunctiva, nose and lower lip all shared similar findings, including prominent lymphoid hyperplasia with germinal center formation. This was accompanied by a mixed dermal infiltrate of lymphocytes and eosinophils. There was no evidence of vasculitis. The overlying epidermis of the nose and lower lip displayed mild epidermal hyperplasia. Immunostains of CD3 and CD20 of both the conjunctival and nasal biopsies highlighted a ratio of T cells and B cells that was within normal range. The periodic acid–Schiff stain of the nasal biopsy showed a normal appearing basement membrane and no evidence of fungal elements. Tissue culture from the nasal biopsy was negative for anaerobes, acid-fast bacilli and fungi, and grew a moderate amount of Staphylococcus aureus.
Our patient was instructed to adhere to strict sun protection, including use of 100% UV protective eyewear and a sunscreen with a SPF of 85 to her lips. Impetigo of the nasal plaque was treated with doxycycline 100 mg twice daily for 3 weeks. Within 3 months of starting vitamin C 1 g daily, betamethasone dipropionate 0.05% ointment and following strict sun protection, there was complete resolution of the plaque on her lip and significant improvement of the plaque on her nose. The patient also noted some improvement in her ocular symptoms.
Conclusion
Actinic prurigo is a rare, chronic photodermatosis that presents with pruritic erythematous, crusted papules and nodules. These lesions typically appear hours to days after exposure to UV light on sun-exposed skin. The mainstay of treatment is vigorous sun protection, though topical and short courses of oral corticosteroids may be useful for acute exacerbations. Thalidomide is an effective therapy for recalcitrant cases.
Dr. Fabi is with Goldman Butterwick Fitzpatrick Groff & Fabi, Cosmetic Laser Dermatology in San Diego, CA.
Dr. Vanaman is with the department of dermatology at the University of Illinois at Chicago-College of Medicine in Chicago, IL.
Dr. Aronson is with the department of dermatology at the University of Illinois at Chicago-College of Medicine in Chicago, IL.
Disclosure: The authors report no relevant financial relationships.
References
1. Ross G, Foley P, Baker C. Actinic prurigo. Photodermatol Photoimmunol Photomed. 2008; 24(5):272-275.
2. Castanedo-Cazares JP, Moncada B, Torres-Alvarez B. Actinic prurigo. Medscape website. https://emedicine.medscape.com/article/1120153-overview.
Updated June 25, 2013. Accessed April 17, 2014.
3. Hojyo-Tomoka MT, Vega-Memije ME, Cortes-Franco R, Dominguez-Soto L. Diagnosis and treatment of actinic prurigo. Dermatol Ther. 2003;16(1):40-44.
4. Santos-Martinez L, Llorente L, Baranda L, et al. Profile of cytokine mRNA expression in spontaneous and UV-induced skin lesions from actinic prurigo patients. Exp Dermatol. 1997;6(2):91-97.
5. Herrera-Geopfert R, Magana M. Follicular cheilitis. A distinctive histopathologic finding in actinic prurigo. Am J Dermatopathol. 1995;17(4):357-361.
6. Magana M, Mendez Y, Rodriguez A, Mascott M. The conjunctivitis of solar (actinic) prurigo. Pediatr Dermatol. 2000;17(6):432-435.
7. Lestarini D, Khoo LS, Goh CL. The clinical features and management of actinic prurigo: a retrospective study. Photodermatol Photoimmunol Photomed. 1999;15(5):183-187.
8. McCoombes JA, Hirst LW, Green WR. Use of topical cyclosporin for conjunctival manifestations of actinic prurigo. Am J Ophthalmol. 2000;130(6):830-831.
