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| Gary M. White & Neil H. Cox |
| Diseases of the Skin |
17 |
Photodermatology and Photodermotosess |
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DERMATOSES THAT MAY BE AGGRAVATED BY SUNLIGHT
Examples of dermatoses that may be aggravated by sunlight are listed in Table 17.10. Some of these are characteristically provoked by sunlight, and the relationship is usually apparent, such as lupus erythematosus and pellagra. Similarly, some patients who have dermatomyositis have a striking cut-off of lesional skin at areas such as the nape or V of the neck. Other conditions, such as disseminated super?cial actinic porokeratosis, may be much less clearly related to sunlight or may be related to heat and humidity rather than to sunlight (e.g. Hailey–Hailey disease).
Several of the disorders that may be sunlight-aggravated can also demonstrate a Koebner (isomorphic) reaction to minor injury, for example psoriasis (Fig. 17.55) and pemphigus.
In most examples, other than documenting the patient's experience and the distribution of the skin eruption, there are no useful tests to distinguish which individuals will have problems with photoaggravation. However, in lupus erythematosus, it can be predicted that some individuals, notably those who have subacute cutaneous lupus erythematosus and other anti-SSA (anti-Ro)-positive patients, will have a more obvious sunlight aggravation of their disease.
Disorders that are typically improved by sunlight, but may worsen in some individuals, are of interest. They include disorders such as psoriasis, atopic dermatitis, and acne. The mechanisms involved are uncertain, but the type and timescale of provocation are often consistent for any individual. The tendency for photoaggravated psoriasis to be a problem in women rather than in men suggests that it may represent a Koebner reaction in PLE in some cases. Some patients who have psoriasis of this type respond well to PUVA, or even to narrow-band (311-nm) UVB if the reaction is triggered by UVA.
In general, other than sun protection, the treatments are standard for each of the different disorders and are discussed in the relevant chapters of this book.
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figure 17.55 Psoriasis aggravated by sunlight. This is a seasonally recurrent problem, which occurs mainly in women. Note the relative sparing of the wrists. |
| Association with sunlight | Dermatosis |
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| Frequently sunlight-provoked | Lupus erythematosus Dermatomyositis Reticulate erythematous mucinosis (REM) syndrome Darier disease Pellagra Herpes simplex |
| Variably sunlight-provoked | Transient acantholytic dermatosis (Grover disease) Pemphigus (especially foliaceous and erythematosus types) Rosacea Disseminated super?cial actinic porokeratosis Hailey–Hailey disease |
| Usually unrelated to sunlight, but provoked in occasional cases | Lichen planus Erythema multiforme Granuloma annulare |
| Usually improve in sunlight, but aggravated in some cases | Psoriasis Atopic dermatitis Acne Cutaneous T-cell lymphoma |
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White/Cox: Diseases of the Skin, 2ed.(c) 2006, Elsevier Inc. All rights reserved.