Actinic prurigo: (Synonyms: hereditary polymorphic light eruption of American Indians, Hutchinson’s summer prurigo, photodermatitis in North American Indians)

Published on 19/03/2015 by admin

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Actinic prurigo

(Synonyms: hereditary polymorphic light eruption of American Indians, Hutchinson’s summer prurigo, photodermatitis in North American Indians)

Robert S. Dawe

Evidence Levels:  A Double-blind study  B Clinical trial ≥ 20 subjects  C Clinical trial < 20 subjects  D Series ≥ 5 subjects  E Anecdotal case reports

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Actinic prurigo (AP) is a distinct photodermatosis, diagnosed on the basis of characteristic clinical features including perennial (albeit worse in summer) nature, vesiculopapular eruption during acute flares, persistent eroded nodules and/or dermatitic patches (sometimes affecting covered sites), scarring, dorsal nose involvement, cheilitis and conjunctivitis. Abnormal photosensitivity (UVA, UVB) is frequently severe, but generally gradually improves, especially when (as is usual) it presents before the age of 10 years.

Management strategy

Diagnosis is normally straightforward, but the differential diagnosis can include severe polymorphic light eruption and photoaggravated atopic dermatitis. Although differences between European and Amerindian forms of AP have been described, these are either closely related conditions or the same disease with some differences affected by population and environment. Phototesting and HLA typing may sometimes be helpful in cases of diagnostic uncertainty. Possible coexisting conditions such as sunscreen allergic contact dermatitis or photocontact reactions should be considered, as their presence will affect the recommended treatments.

Once the diagnosis is established, initial treatment consists of advice on sunlight avoidance measures (behavioral, clothing, and topical sunscreen), and the use of potent or very potent topical corticosteroids. This approach alone is often insufficient, and many patients require the addition of a springtime course of narrowband (TL-01) UVB or PUVA. When phototherapy is administered for this indication, only normally sunlight-exposed sites should be treated. It is helpful to apply a potent topical steroid to the treated areas immediately after each exposure, to reduce the risk of AP flares.

In Scotland, systemic treatment is rarely required, but is more often necessary where the availability of phototherapy is limited and in countries with more intense year-round sunlight exposure. Antimalarials and β-carotene are sometimes tried, but it remains uncertain whether they are truly of value. Thalidomide may be more useful, but its value is restricted by teratogenicity and the risk of irreversible peripheral neuropathy. Pentoxifylline has anti-TNF-α effects and, although listed as a third-line therapy here, may be worth considering before thalidomide because of its more attractive safety profile.

Specific investigations

Actinic prurigo: clinical features and HLA associations in a Canadian Inuit population.

Wiseman MC, Orr PH, MacDonald SM, Schroeder ML, Toole JW. J Am Acad Dermatol 2001; 44: 952–6.

No statistically significant association of AP with HLA-DR4 (frequent in the studied population) or HLA-DRB1*0407 was detected, and another HLA type (DRB1*14) was found more commonly than expected, although it was only present in 19 of 37 AP subjects. The authors acknowledge the possibility that they were studying a different condition from AP in other populations. Nevertheless, these findings suggest we should be cautious in attempting to use HLA typing as a diagnostic test, especially in populations in which strong HLA associations have not been confirmed. The diagnosis should still be based on the characteristic constellation of clinical features.

First-line therapies

image Sunlight avoidance – environmental, behavioral, clothing, topical sunscreen C
image Potent/very potent topical corticosteroids C
image Narrowband (TL-01 lamp) UVB phototherapy C

Second-line therapies

image Psoralen–UVA photochemotherapy C
image Thalidomide C

Third-line therapies

image β-Carotene C
image Pentoxifylline C
image Tetracycline and vitamin E C
image Oral corticosteroids E
image Azathioprine E
image Chloroquine E
image Cyclosporine eye drops E

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