97 - Phototoxicity and Photoallergy Flashcards
Well-characterized examples of photosensitivity induced by endogeneous photosensitizers are the
Cutaneous porphyrias
Result of direct tissue injury caused by the phototoxic agent and radiation
Phototoxicity
Type IV delayed hypersensitivity response to a molecule that has been modified by absorption of protons
Photoallergy
Most of the photosensitivity induced by systemic medications are _____, whereas those induced by topical agents are _____
Phototoxicity
Photoallergy
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
Photoonycholysis has been reported with
Doxycycline and other tetracyclines Fluoroquinolones Psoralens Benoxaprofen Clorazepate dipotassium Olanzapine Aripiprazole Indapamide Quinine
Asymptomatic blue-gray pigmentation on sun-exposed areas is associated with exposure to several agents
Amiodarone Chlorpromazine Clozapine Imipramine Despiramine Minocycline Diltiazem Silver
Can induce blue-gray pigmentation on sun-exposed areas such as face, frequently on sites of acne scars, forearms, and shins
Minocycline
Slate-gray pigmentation involves the nail lunulae, mucous membranes, and sclerae
Silver granules are deposited in the dermis
Argyria
Cutaneous changes of skin fragility, vesicles, and subepidermal blisters
Porphyrin profile is normal or in the upper range of normal
Pseudoporphyria
Most commonly reported causative agent of pseudoporphyria
Naproxen
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
Accelerated photo-induced changes has been uniquely described with
Voricanozole
Photodistributed telangiectasia has been reported with
Calcium channel blockers (nifedipine, amlodipine, felodipine, diltiazem)
Cefotaxime
Antidepressants (venlafaxine, escitalopram)
Lichenoid photosensitive eruption has been reported with
Doxycycline
Capecitabine
Persistence of photosensitivity and evolution to chronic actinic dermatitis has been reported with
Thiazides
Quinidine
Quinine
Amiodarone
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
