Diagnosis

Photosensitivity

An inflammatory skin disease caused by the combination of a chemical and light exposure [yhp][z2q][oep]

  • Phototoxic: common, large amount of agent required, may involve unexposed areas

  • Photoallergic: rare, small amount of agent required, strictly sun-exposed

  • Photosensitive epilepsy: A “photoparoxysmal” response to photic stimulation [p1p]

Etiology

Cause [z2q]

  1. Primary (autoimmune) photodermatoses:

    Polymorphic light eruption, Juvenile spring eruption, Actinic folliculitis, Actinic prurigo, Solar urticaria, Chronic actinic/photosensitivity dermatitis, Hydroa vacciniforme

  2. Exogenous (drug/chemical-induced) photodermatosis: thiazides, tetracyclines, NSAIDs, phenothiazines, voriconazole, quinine, vemurafenib, psoralen (plants, vegetables, fruit), fragrances (cosmetics), sunscreen chemicals, dyes and disinfectants

  3. Photo-exacerbated dermatoses: Cutaneous lupus erythematosus, lupus erythematosus, Sjogren syndrome, Darier disease, Rosacea, Melasma, Pemphigus vulgaris, Pemphigus foliaceus, Atopic dermatitis, Seborrhoeic dermatitis, Psoriasis, Lichen planus (actinicus), Erythema multiforme, Mycosis fungoides

  4. Metabolic photodermatosis (rare): Porphyria cutanea tarda, Erythropoietic protoporphyria, Variegate porphyria, Erythropoietic porphyria (Gunther disease)

  5. Genetic photodermatosis (very rare): Xeroderma pigmentosum, Cockayne syndrome, Trichothiodystrophy, Bloom syndrome, Rothmund Thomson syndrome

Pathophysiology

  1. Phototoxic: common, direct damage to tissue caused by a photoactivated compound

    • Pathophysiology of photoactivation:

      UV-A (320-400 nm) -> excitation of electrons -> excited-state electrons return to a more stable configuration -> release of energy -> formation of reactive oxygen intermediates -> damage cell membranes and DNA -> inflammatory response -> exaggerated sunburn reaction

    • Phototoxic agents:

      • Antibiotics (Tetracyclines, Fluoroquinolones, Sulfonamides)

      • NSAIDs (also photoallergic)

      • Statins (also photoallergic)

      • Antifungals (also photoallergic)

      • Amiodarone

      • Neuroleptics

      • Diuretics

      • Retinoid

      • Sulfonylurea

      • Porphyrin

      • Coal

      • Drugs

      • Psoralen

  2. Photoallergic: rare, cell-mediated immune responses in which the antigen is a light-activated drug

    • Pathophysiology of photoallergy:

      Antigen-presenting Langerhans cells migrate to regional lymph nodes and present photoallergen -> T cells become activated, proliferate and migrate to the site of photoallergen deposition -> T cells orchestrate an inflammatory response -> eczematous morphology

    • Photoallergic agents:

      • Sulfonylurea

      • Dapsone

      • Oral contraceptives

      • Sunscreens

      • Fragrances

Epidemiology

Incidence per 100.000

Epidemiology chart for Incidence

Symptoms & findings

Symptoms

Onycholysis, Seizure

Clinical findings

None listed.

Anamneses

None listed.

Localized findings

Rash
Radiates
CaputCollumThoraxAbdomenGenitalArmBackLower body
Distribution
MultiplePhotodistributedSymmetric
Lesion type
BullaErythemaHyperpigmentationLichenificationPapulePlaqueScaleVesicle
Color
Red
Associated symptom
PainSwelling
Palpation
Pain

Approach

Treatment

  1. Sun protection: Avoid direct sunlight, covering clothing, sunscreen

  2. Treatment of the underlying disorder

Differential diagnoses

Acute intermittent porphyria, Dermatomyositis, Drug eruptions, Eczema, Epidermolysis bullosa, Epilepsy, Lichen planus, Systemic lupus erythematosus, Urticaria

References

[1] http://emedicine.medscape.com/article/1049648; [Medscape]

[2] Oakley AM, Badri T, Harris BW. Photosensitivity. Updated 2023 Aug 8: https://www.ncbi.nlm.nih.gov/books/NBK431072/

[3] Inamadar AC, Palit A. Photosensitivity in children: An approach to diagnosis and management. Indian J Dermatol Venereol Leprol 2005;71:73-9.

[4] Verrotti A, Beccaria F, Fiori F, Montagnini A, Capovilla G. Photosensitivity: epidemiology, genetics, clinical manifestations, assessment, and management. Epileptic Disord. 2012 Dec;14(4):349-62.

[5] de Bittencourt PR. Photosensitivity: the magnitude of the problem. Epilepsia. 2004;45 Suppl 1:30-4.

[6] https://www.uptodate.com/contents/photosensitivity-disorders-photodermatoses-clinical-manifestations-diagnosis-and-treatment

[7] Burfield L, Rutter KJ, Thompson B, Marjanovic EJ, Neale RE, Rhodes LE. 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 Mar;37(3):511-520.

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