Questioning and well conducted clinical examination usually allow to reach the diagnosis. Dermatitis caused by light is suspected by the concept of sun exposure before the onset of lesions and topography affecting sun-exposed areas (face, forearms, chest, legs). These dermatoses may occur after intense sun exposure and / or unusual and, in some cases, after a normal sun exposure. Inspection notes topography and appearance of the rash.
Sun exposure characteristics are sought and the time to onset compared to the exposure. Personal history, family, drugs used, the use of topical or exposure to toxic, pruritus, burning sensation are specified.
The sun-exposed areas affected are often clearly delimited by clothing.
Legs, back legs (especially in women), neck, forearms, face, neck and back of the hands are the most affected areas.The rash may overflow photo-exposed areas and achieve the covered areas (photoallergic mechanism).
The face can be observed in benign summer light eruption.
Symptoms of dermatitis caused by light are:
– Monomorphic appearance of lesions (erythema similar to a sunburn). Phototoxic reaction is involved (think of drugs and topical sensitizers);
– Polymorphic nature of injury (érythématovésiculeuses with eczema lesions, oozing, erosion, crusting, poorly defined), urticaria with transient papules, mobile and migratory, papulovesicles excoriated, cocardiformes.Photoallergic reaction is involved;
– Other associated lesions (pemphigoid bubbles vespertilio, etc.);
– Fragile skin with pigmentation and hypertrichosis (late cutaneous porphyria);
– Fissure cheilitis, angular cheilitis, stomatitis (vitamin deficiencies, especially PP);
– Freckles, mottled lesions, lentigines, tumors in favor of Xeroderma pigmentosum;
– Blue sclera, hypochromia for a Oculocutaneous albinism.
A general review is of course necessary.
Liver function tests, iron, an HIV serology (active immunodeficiency virus) and HCV (Hepatitis C), the porphyrins in the urine assay is requested for late cutaneous porphyria suspicion.
If lupus suspicion, FAN (anti-nuclear factors), NFS (complete blood count) platelets, ESR (erythrocyte sedimentation rate), urea, blood creatinine assay of complement and proteinuria 24 hours may be requested.
Additional tests (skin biopsy, photobiological explorations) are the responsibility of the specialist.
Rare, génophotodermatoses are related to a deficiency of photoprotection. Xeroderma pigmentosum include the, albinism, Cockayne syndrome, etc.
The most common is porphyria cutanea tarda, appearing in an HIV or chronic HCV patient, often ethyl, combining hypertichose bubbles on sun-exposed areas after sun exposure and hyperpigmentation.
The diagnosis is based on the determination of blood and urinary porphyrins.
Treatment is based on the Plaquenil® low dose (200 mg Plaquenil® 2 × 2 per week) and avoidance of drug predisposing factors. The associated disease is researched and processed.
The other porphyrias are exceptional.
Pellagra is seen in the subject malnourished, especially ethyl. It combines with dry skin atrophy and erythema, mucosal lesions (cheilitis, stomatitis, angular cheilitis), and photosensitivity.
Treatment is based on parenteral administration of niacin (pellagra preventiva).
Congenital abnormalities of tryptophan metabolism are the responsibility of the pediatrician.
The skin disease is exacerbated by sun exposure, which can trigger breakouts.
These include lupus, acne, rosacea, pemphigus and bullous pemphigoid, labial herpes recurrences.
The rash of dermatomyositis often predominates on sun-exposed areas (eyelid edema Liliace, rash neckline and arms, etc.)
Light acts on a photosensitizing molecule present in the skin.
Phototoxicity is related to the properties of the molecule. It occurs in all subjects exposed in the first exposure. In type of sunburn, it localizes to open areas, and is even more serious than the dose is important. The examination is the notion of toxic outlet (often drug) photosensiblisant (cyclins, retinoids, dyes, plant, psoralen, etc.).
Photoallergy is linked to an individual susceptibility.
It comes after several exhibitions and can escape the areas covered. It has a polymorphic appearance (eczema, prurigo, lichenoid, etc.) and can be extended (risk of residual photosensitivity). Plants with sesquiterpene lactones and drugs (phenothiazines, etc.) may be involved.
Treatment is based on the eviction of the product photosensitizer, the photoprotection (type Photoderm max®) and local corticosteroids (Diprosone® cream tapering).
Resistant or prolonged cases are confi ed to the specialist.
Photodermatoses without photosensitizer:
This is idiopathic light eruptions.
Winter and summer light eruption:
Polymorphous light eruption is the most common.
It is found more in women and appears in the aftermath of intense sunlight exposure, in practice the summer. It affects sun-exposed areas, but respects the face. It consists of very small pruritic papules, sometimes vesicular erythematous.
The rash fades over sun exposure, but may recur the following year.
The mild winter lucite occurs in the winter, mostly affects the face with edematous and pruritic papules and plaques.
Treatment is based on photoprotection, decision Plaquenil® 200 mg / day to begin ten days before departure and continue during the stay, rarely PUVA. Curative treatment is based on topical corticosteroids.
Juvenile Spring Eruption:
The Juvenile Spring photodermatosis touch the boy with selective involvement of the ear (papules vesicular the free edge of the helix), often in the spring.
There must be a cap.
Polymorphic Light Eruption:
Polymorphic light eruption is rarer than benign summer light eruption. It is opposed by some points polymorphous light eruption:
– Early spring to the usual sun exposure;
– Maximum occurred within hours after exposure;
– Achievement of open areas and face;
– Polymorphic nature (papules, vesicles, cocardiformes, etc.);
– Does not tend to fade over exhibitions but disappeared about three weeks after cessation of exposure.
Photobiological explorations allow to confirm the diagnosis.
Photoprotection should be used, even in cases of exposure from everyday life.
Preventive treatment is otherwise identical to that of the polymorphous light eruptions.
Solar urticaria is rare. It occurs around 30 to 40 years, within minutes of intense sunlight exposure, or occasionally on generally open areas. He returned in the summer when sun exposure increasingly strong.
Photobiological explorations are indicated.
Curative treatment uses the H2 antihistamines, preventive treatment for the photoprotection and PUVA.
The hydroa vacciniforme rarely begins in childhood and disappears around 20 years. After prolonged sun exposure appear within 48 hours of vesicles on erythematous base and crusts with depressed scars, especially in summer.The face, back of the hands and forearms are achieved.
The patient is assigned to a specialist (biopsy dosage porphyrins, photobiological exploration) for a mostly phototherapy treatment.
Residual photosensitivity syndrome:
The residual photosensitivity syndrome affects rather the man in his fifties with a history of photoallergy.Photosensitivity is extreme, sometimes preventing exposure to daylight. The appearance is that of an eczema on sun-exposed areas extending into the areas covered.
The patient is entrusted to the specialist.