In polymorphous light dermatosis (synonyms: benign summer light eruption; hydroa aestivalia; hydroa vacciniformia; juvenile spring eruption; light dermatosis; lucite estivale benigne; photodermatitis multiformis acuta; photodermatosis; polymorphous light dermatosis; polymorphous light eruption due to sun exposure; polymorphus light eruption; prurigo aestivalis; summer prurigo; sun allergy; sunlight allergy; ICD-10 L56. 4: Polymorphous light dermatosis) is a delayed light reaction of the skin, which is accompanied by various efflorescences (skin changes).
It is the most common photodermatosis, accounting for 90% of all light-induced skin changes.
Seasonal accumulation of the disease: polymorphous photodermatosis often occurs seasonally in a chronic recurrent manner, often in spring or early summer (March to June), after the first exposure to sunlight.
Three main types of polymorphous light dermatosis can be distinguished:
- Papular type – most common type with small papules (“vesicles”) on patchy erythema (areal redness of the skin).
- Hemorrhagic type – in addition to papules on erythema, erythrocyte extravasations occur.
- Small papule type (pinhead type).
- Papulovesicular type – appearance of papules, papulo-vesicles, vesicles and bullae (blister).
- Ictus type (insect bite type).
- Vesiculo-bullous type – extreme variant with vesicles and bullae.
- Plaques type – sharply demarcated plaques (areal or plate-like substance proliferation of the skin), often occurring on the face.
- Erythema exudativum multiforme type – cocard-like lesions.
Sex ratio: women seem to be affected more often than men.
Frequency peak: The disease occurs predominantly in children and adults in young and middle age.
The prevalence (disease frequency) is between 10 and 20%, with an increasing trend (in Central Europe, Scandinavia, USA).
Course and prognosis: The disease progresses in episodes after intense UV exposure. The skin changes appear after a few hours to a few days, but subside within a few days without scarring if sun exposure is avoided. Over time, the episodes become weaker (habituation effect). Prophylaxis is of great importance. By getting used to light by means of, for example, phototherapy up to general light protection measures (sunscreen with a high sun protection factor, wearing caps/hats, etc.), the affected person can prevent or reduce the intensity of the symptoms.
