Photodermatitis

Essentials of Diagnosis

• Painful or pruritic erythema, edema, or vesiculation on sun-exposed surfaces: the face, neck, hands, and "V" of the chest

• Inner upper eyelids spared, as is the area under the chin

General Considerations

• Photosensitivity is an acute or chronic inflammatory skin reaction due to hypersensitivity to ultraviolet radiation

• Medications that can cause photosensitivity include

  • Vemurafenib

  • Nonsteroidal anti-inflammatory drugs

  • Voriconazole

  • Tetracyclines

  • Quinolones

  • Hydrochlorothiazide

  • Amiodarone

  • Chlorpromazine

• Other potent photosensitizers include

  • Trimethoprim-sulfamethoxazole

  • Quinine or quinidine

  • Griseofulvin

  • Eculizumab

  • Topical and systemic retinoids (tretinoin, isotretinoin, acitretin)

  • Calcium channel blockers

• Contact photosensitivity may occur with plants, perfumes, and sunscreens

• Three percent of persons with atopic dermatitis, especially middle-aged women, are photosensitive

Symptoms and Signs

• Acute inflammatory phase of phototoxicity, which, if severe enough, is accompanied by pain, fever, gastrointestinal symptoms, malaise, and even prostration

• Erythema, edema, and possibly vesiculation and oozing on exposed surfaces

• Peeling of the epidermis and pigmentary changes often result

• The lower lip may be affected

Differential Diagnosis

• Contact dermatitis

• Porphyria cutanea tarda

• Systemic lupus erythematosus

• Polymorphous light eruption (PMLE)

Laboratory Tests

• The key to diagnosis is localization of the rash to photoexposed areas, though these eruptions may become generalized with time to involve photoprotected areas

• Blood and urine tests are not helpful in diagnosis unless porphyria cutanea tarda is suggested by the presence of blistering, scarring, milia (white cysts 1–2 mm in diameter) and skin fragility of the dorsal hands, and facial hypertrichosis

• Eosinophilia may be present in chronic photoallergic responses

Medications

• Medications should be suspected in cases of photosensitivity even if the particular medication (such as hydrochlorothiazide) has been used for months

LOCAL MEASURES

• When the eruption is vesicular or weepy, treatment is similar to that of any acute dermatitis, using cooling and soothing wet dressing

• Mid-potency to high-potency topical corticosteroids are of limited benefit in sunburn reactions but may help in polymorphous light eruption and photoallergic reactions

• Since the face is often involved, close monitoring for corticosteroid side effects is recommended

SYSTEMIC MEASURES

• Aspirin may have some value for fever and pain of acute sunburn, as prostaglandins appear to play a pathogenetic role in the early erythema

• Systemic corticosteroids in doses as described for acute contact dermatitis may be required for severe photosensitivity reactions

• Immunosuppressives may be indicated for severe photoallergy, such as azathioprine, in the range of 50–300 mg daily orally; or cyclosporine, 3–5 mg/kg/day orally

Prognosis

• The most common phototoxic reactions are usually benign and self-limited

• Polymorphous light eruption and some cases of photoallergy can persist for years

Prevention

• While sunscreens are useful agents in general and should be used by persons with photosensitivity, patients may react to such low amounts of energy that sunscreens alone may not be sufficient

• Sunscreens with an SPF of 30–60 and broad UVA coverage, containing dicamphor sulfonic acid (Mexoryl SX), avobenzone (Parasol 1789), titanium dioxide, and micronized zinc oxide, are especially useful in patients with photoallergic dermatitis

When to Refer

• If there is a question about the diagnosis, if recommended therapy is ineffective, or if specialized treatment is necessary