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KristiinaAirola

Photodermatitis

Essentials

  • Ultraviolet (UV) radiation from the sun or, more rarely, visible light can provoke a rash either
    • alone without contributing factors (idiopathic photodermatitis)
    • in combination with an ingested or externally applied medicine
    • in combination with a chemical substance on the skin (e.g. phytophotodermatitis associated with plant contact)
  • UV radiation may also trigger certain skin conditions or worsen their symptoms.
  • Protecting the skin against the sun is paramount as is the avoidance of known offenders.
  • Treatment consists of glucocorticoids either topically or orally, or of antihistamines for solar urticaria.

Idiopathic photodermatitis

  • Polymorphous light eruption (PMLE or PLE; picture )
    • By far the most common form, more common in women. Prevalence varies from country to country, ranging from less than 1% (China) to 21% (Ireland) of the population http://onlinelibrary.wiley.com/doi/10.1111/jdv.18772.
    • Onset usually at the age of 20-30 years; may resolve over the years.
    • Typically encountered in the spring and early summer, with symptoms occurring within a few hours of UV exposure and continuing for a few days, sometimes longer.
    • Itchy papules, vesicles or plaques most often on the backs of the hands, forearms and chest, sometimes also on the face.
    • In some patients, tolerance to the sun will increase as the summer progresses, and they will have no symptoms towards the end of the summer. However, the symptoms will recur the next spring/summer.
    • This is probably a delayed type IV allergic reaction caused by a protein induced by UV light (a photoallergen).
    • Subtypes of PMLE include juvenile spring eruption, which causes vesicles on the auricles in young boys, and the very rare hydroa vacciniforme occurring in children and causing blisters in areas exposed to light.
    • Actinic prurigo is a rare mainly facial photodermatitis that begins in childhood. The disease occurs especially in Native Americans.
  • Solar urticaria
    • A rare form of physical urticaria
    • Occurs as urticarial wheals or in some cases as just itching and erythema on sun exposed skin areas, occasionally as a result of minimal sun exposure.
    • Symptoms develop within minutes, and resolve in a few hours.
    • Tolerance will increase but not to the same degree as in PMLE. In a small share of patients, the symptoms resolve over the years.
  • Chronic actinic dermatitis
    • Uncommon, occurs mainly in elderly men.
    • Photosensitivity and chronic eczema in light exposed areas that may spread to other skin areas
    • Often in people with a history of a chronic skin condition (atopic eczema or contact allergy to metals or perfumes, for example).
    • Symptoms erupt slowly and may progress to cutaneous lymphoma.

Photodermatitis induced by medicines or chemicals

  • Exposure to an exogenous substance combined with UV radiation may cause a photoirritant (phototoxic) reaction or a photoallergic reaction.
  • The photosensitising substance can sometimes be an endogenous origin metabolite (see porphyrias Porphyrias).

Drug-induced photodermatitis

  • Most commonly caused by UVA radiation transmitted also through windows.
  • Phototoxic responses are more common, are dose dependent, and usually develop soon after the beginning of medication, provided that the light exposure is sufficiently intense.
    • Usually triggered by internally used drugs. Drug history should be obtained, including natural remedies.
    • Symptoms are similar to sunburn and are strictly limited to exposed areas of the skin. There is only mild pruritus.
  • Drug photoallergic responses usually only develop after light exposure in association with repeated or long-term drug administration.
    • Erythematous rash, which usually resembles eczema, extends beyond the light-exposed area and is combined with severe pruritus (picture ).
    • Topical drugs applied to the skin, such as an NSAID gel or ointment, may cause allergic photocontact dermatitis.

Photocontact dermatitis

  • Phytophotodermatitis is caused by skin contact with a plant containing psoralens (furocoumarins), e.g. gas plant or umbelliferous plants, such as giant hogweed or garden angelica (pictures ) in association with UV radiation.
  • Allergic photocontact dermatitis can be triggered by, for example, chemicals used as perfumes or in sunscreens or by topical NSAIDs.

Common drugs with photosensitising effects

Cardiac and anti-hypertensive drugsPsychotropic drugs
Thiazide diuretics; hydrochlorothiazide, in particular
Furosemide
Antiarrhythmic drug amiodarone
Traditional antipsychotic drugs in the phenothiazine group, such as chlorpromazine, levomepromazine and perphenazine
AntimicrobialsNon-steroidal anti-inflammatory drugs (NSAIDs)
Doxycycline, tetracycline
Fluoroquinolones, such as ciprofloxacin or levofloxacin
Sulfonamides
Antifungal drug voriconazole
Naproxen
Ketoprofen and piroxicam (particularly when used topically)
Antineoplastic agentsOthers
Fluorouracil
Tegafur
Cabecitabine
Vinblastine
Dacarbazine
Methotrexate
Protein kinase inhibitors vemurafenib, vandetanib, dabrafenib, imatinib
Chloroquine and hydroxychloroquine
Fenofibrate
Pirfenidone
Retinoids, such as isotretinoin, acitretin, alitretinoin
Topical drugs for acne: retinoid ointments and benzoyl peroxide
Natural remedies
St. John's wort (Hypericum perforatum)

Diseases exacerbated by light

History and clinical picture

  • The history is the most important aspect of diagnosis, particularly in the diagnosis of PMLE and solar urticaria.
  • A drug history should be obtained, as well as a history of possible exposure to chemicals or plants.
  • Photodermatitis or drug-induced photodermatitis can be suspected if the rash is limited to the areas of skin exposed to light. Unexposed areas are often unaffected (inner aspect of the arms, under the jaw, behind the ears and all areas covered by clothing).
  • An important piece of information for differential diagnosis is how long it took for the symptoms to erupt when the patient was exposed to sun, and how long it took for them to disappear after the end of sun exposure (minutes in solar urticaria, hours-days in PMLE, days-weeks in chronic actinic dermatitis).
  • The appearance of the rash varies between the different types of photodermatitis: erythema, urticaria, papules, vesicles, blisters, eczema, lichenification.
  • Increased tolerance as the summer progresses
    • Characteristic especially in PMLE, but hardly ever occurs in drug-induced photodermatitis.
  • Photodermatitis often has a typical age of onset.

Diagnosis and differential diagnosis

  • Specific phototests (minimal erythema dose, photoprovocation and photopatch tests) are very rarely indicated
    • E.g. in university hospitals
  • Epicutaneous tests are important in the diagnostic workup if photodermatitis with eczematous symptoms is suspected.
    • Contact allergies (particularly to cosmetics) are important in differential diagnosis.
    • In chronic actinic dermatitis, the patient often has a history of contact allergy, for example to metals, rubber or plant chemicals.
  • The possibility of a disease aggravated by light must be borne in mind, and specific tests may be indicated.

Treatment

Prevention

  • In drug-induced and photocontact dermatitis, avoidance of the offending substance
  • Protection against UV radiation
    • Clothing
    • Avoidance of being exposed outdoors to the midday sun
    • Appropriate use of sunscreens
  • Phototherapy (small doses initially, doses gradually increased)
    • Used to some extent in the treatment of PMLE, in particular
    • Must be repeated every year
    • The types of light therapy used are: UVB, UVA, SUP or PUVA. A course consists of 15-20 sessions.

Treatment of symptoms

  • Topical treatment
  • Systemic drug therapy
    • Solar urticaria: antihistamines, doses larger than normal are frequently needed. In cases that are difficult to treat, the injectable biological agent omalizumab may be warranted.
    • In PMLE, a short course of oral glucocorticds (such as prednisolone) may be considered. Some patients may benefit from beta-carotene or hydroxychloroquine.
    • Chronic actinic dermatitis will often require an oral course of glucocorticds or, when prescribed by a specialist physician, other immunosuppressive drugs.

    References

    • Burfield L, Rutter KJ, Thompson B, et al. Systematic review of the prevalence and incidence of the photodermatoses with meta-analysis of the prevalence of polymorphic light eruption. J Eur Acad Dermatol Venereol 2023;37(3):511-520 [PubMed]
    • Kadurina M, Kazandjieva J, Bocheva G. Immunopathogenesis and management of polymorphic light eruption. Dermatol Ther 2021;34(6):e15167 [PubMed]
    • Sibaud V. Anticancer treatments and photosensitivity. J Eur Acad Dermatol Venereol 2022;36 Suppl 6(Suppl 6):51-58 [PubMed]
    • Kim WB, Shelley AJ, Novice K, et al. Drug-induced phototoxicity: A systematic review. J Am Acad Dermatol 2018;79(6):1069-1075. [PubMed]
    • Lim HW, et al. Photodermatologic disorders. In book: Bolognia J, Schaffer J, Cerroni L. Dermatology. 4th edition. Elsevier 2017; s. 1548-1568.