97 - Phototoxicity and Photoallergy Flashcards by dvojnd rivera

Well-characterized examples of photosensitivity induced by endogeneous photosensitizers are the

Cutaneous porphyrias

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Result of direct tissue injury caused by the phototoxic agent and radiation

Phototoxicity

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Type IV delayed hypersensitivity response to a molecule that has been modified by absorption of protons

Photoallergy

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Most of the photosensitivity induced by systemic medications are _____, whereas those induced by topical agents are _____

Phototoxicity

Photoallergy

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Acute phototoxicity occurs within hours of exposure to the phototoxic agent and UV radiation. A notable exception to these kinetics is

Psoralen-induced phototoxicity

Acute response first appears after 24 hours, and peaks at 48 to 72 hours

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Photoonycholysis has been reported with

Doxycycline and other tetracyclines
Fluoroquinolones
Psoralens
Benoxaprofen
Clorazepate dipotassium
Olanzapine
Aripiprazole
Indapamide
Quinine

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Asymptomatic blue-gray pigmentation on sun-exposed areas is associated with exposure to several agents

Amiodarone
Chlorpromazine
Clozapine
Imipramine
Despiramine
Minocycline
Diltiazem
Silver

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Can induce blue-gray pigmentation on sun-exposed areas such as face, frequently on sites of acne scars, forearms, and shins

Minocycline

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Slate-gray pigmentation involves the nail lunulae, mucous membranes, and sclerae
Silver granules are deposited in the dermis

Argyria

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Cutaneous changes of skin fragility, vesicles, and subepidermal blisters
Porphyrin profile is normal or in the upper range of normal

Pseudoporphyria

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Most commonly reported causative agent of pseudoporphyria

Naproxen

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Other drugs and treatment modality incriminated in pseudoporphyria

Amiodarone
Beta-lactam antibiotics
Celecoxib
Ciprofloxacin
Cyclosporine
Diflunisal
Etretinate
Furosemide
Imatinib
Nabumetone
Nalidixic acid
NB UVB
Oral contraceptives
Oxaprozin
Ketoprofen
Mefenamic acid
Tetracyclines
Tiaprofenic acid
Torsemide
Voriconazole

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Accelerated photo-induced changes has been uniquely described with

Voricanozole

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Photodistributed telangiectasia has been reported with

Calcium channel blockers (nifedipine, amlodipine, felodipine, diltiazem)
Cefotaxime
Antidepressants (venlafaxine, escitalopram)

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Lichenoid photosensitive eruption has been reported with

Doxycycline

Capecitabine

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Persistence of photosensitivity and evolution to chronic actinic dermatitis has been reported with

Thiazides
Quinidine
Quinine
Amiodarone

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Chronic effects are best exemplified by the manifestations in patients who received

Long-term PUVA chemotherapy

Topical photosensitizing agents

Induce exaggerated UV response as a result of their irritant effect on skin

Fluorouracil

Retinoids

Topical phototoxic agents

Fluoroscein
Furocoumarins
Rose bengal
Tar

Present in limes, celery, figs, and parsnips

Furocoumarins

Crude coal tar is well documented to produce a burning and stinging sensation on exposure to UVA known as

Tar smarts

As a rule, the action spectra of systemic agents are in the UVA range; notable exceptions are _____, whose action spectra are in the visible light range

Porphyrins
Fluorescein
Other dyes

Several pathways eventuate in the development of phototoxic tissue damage

Photodynamic process
Generation of photoproducts
Binding to substrate
Inflammatory mediators
Apoptosis

Involves absorption of radiation energy by the photosensitizer and formation of an excited molecule
Subsequent generation of reactive oxygen species result in tissue injury

Photodynamic process

Generation of _____ induced by exposure to radiation can be responsible for tissue injury

Stable photoproducts

An example of this mechanism is the covalent binding of 8-methoxypsoralen to pyrimidine bases of the DNA molecules upon exposure to UVA, which results in the formation of a crosslink between the DNA strands

Binding to substrate

Biologically active products of complement activation, mast cell-derived mediators, eicosanoids, proteases, and polymorphonuclear leukocytes contribute to the development of phototoxicity

Inflammatory mediators

In addition to generating reactive oxygen species, photodynamic therapy is also a potent inducer of

Apoptosis

In the US, Canada, Europe and the UK, common photoallergens include

``` UV filters (benzophenone-3, octocrylene, avobenzone, octinoxate) Topical NSAIDs (ketoprofen, etofenamate) ```

In China, _____ were the most common photoallergens

Chlorpromazine | Para-aminobenzoic acid

All but one of the photoallergens (_____) are also phototoxic

Pyridoxine

Phototesting and photopatch: reaction only at an irradiated site

Photoallergy

Phototesting and photopatch: reaction of equal intensity at both irradiated and covered sites

Allergic contact dermatitis

Phototesting and photopatch: reaction at both sites, but with a higher intensity at the irradiated site

Photoallergy and allergic contact dermatitis

Phototesting and photopatch: well-defined erythema that resolves promptly

Irritant dermatitis

Characterized by involvement of skinfolds on exposed areas, such as the nasolabial folds and the eyelids that receive minimal direct sunlight Also involves exposed areas that are relatively sun protected, such as the postauricual areas and area under the chin

Airborne allergic contact dermatitis

Occur at sites of contact, in both sun-exposed and sun-protected areas

Allergic contact dermatitis | Irritant contant dermatitis

Manifests itself within a few hours of sun exposure as pruritic papules, plaques, and, uncommonly, vesicles on sun-exposed sites and resolves in a few days Lack of exposure to photosensitizer

Polymorphous light eruption

Chronically lichenified plaques on sun-exposed areas | Lack of exposure to photosensitizer

Chronic actinic dermatitis

Appear within minutes of sun exposure as mildly pruritic urticaria and resolve within a few hours Lack of exposure to photosensitizer

Solar urticaria