Photodermatoses: diagnosis and treatment

Abstract

Background: Sunlight induces a wide variety of dermatoses. Their differential diagnosis is problematic not only because of similar phenotypes, but also because of confusing nomenclature and classification.

Methods: We selectively reviewed the literature of the past 20 years and describe the modern nosology of photodermatoses and their clinical features, diagnosis, and treatment. Readers should be able to provide correct and efficient diagnostic evaluation and treatment of patients with dermatoses induced by ultraviolet radiation.

Results: Photodermatoses are caused by an abnormal reaction to sunlight, usually to its ultraviolet component. They are divided into phototoxic and photoallergic reactions to known photosensitizers and idiopathic photodermatoses, in which the photosensitizer is unknown. Some types are extremely rare, such as hydroa vacciniforme (prevalence 0.34 per 100,000), while others are very common, such as polymorphic light eruption (prevalence 10% to 20%).

Conclusion: Photodermatoses are not life-threatening but can cause considerable suffering. Prevention is just as important as treatment.

Figure 1

Spectral range of UV radiation

Figure 2

Polymorphous light eruption; small papular efflorescences 24 hours after sun exposure

Figure 3

Provocation: induction of papules and vesicles after 3 exposures to UV-A radiation (100 J/cm²)

Figure 4

Solar urticaria. Induction of erythema and wheals after radiation with UV-A

Figure 5

Phototoxic dermatitis; streaked erythema after UV exposure; was cutting a bush in the garden immediately beforehand

Figure 6

Photoallergic dermatitis; maculopapular eczema with incipient lichenification in the UV-exposed areas