97: Phototoxicity & Photoallergy Flashcards
(111 cards)
1
Q
What is the likely diagnosis for a patient with burning and stinging on sun-exposed areas after taking a new medication?
A
The likely diagnosis is acute phototoxicity.
2
Q
What is the mechanism behind acute phototoxicity?
A
The mechanism involves direct tissue injury caused by the phototoxic agent and radiation, leading to erythema, edema, and in severe cases, vesicles and bullae.
3
Q
What is the likely explanation for hyperpigmentation lasting for months after PUVA therapy?
A
PUVA therapy involves psoralen-induced phototoxicity, where the acute response peaks at 48-72 hours and resolves with hyperpigmentation that can last for months.
4
Q
What condition is indicated by separation of the distal nail from the nail bed after starting doxycycline?
A
The condition is photoonycholysis.
5
Q
How does photoonycholysis occur?
A
It occurs due to the nail plate acting as a lens to focus UV energy on the nail bed. Doxycycline and other tetracyclines are common culprits.
6
Q
What is the diagnosis for pruritic, eczematous eruptions confined to sun-exposed areas after using a new sunscreen?
A
The diagnosis is photoallergy.
7
Q
What is the mechanism behind photoallergy?
A
The mechanism involves a type IV delayed hypersensitivity response to a photoallergen modified by photon absorption.
8
Q
What are the two main types of photosensitivity?
A
Phototoxicity and photoallergy.
9
Q
What is phototoxicity?
A
Direct tissue injury caused by the phototoxic agent and radiation, occurring in all individuals exposed to adequate doses of the agent and activating wavelengths of radiation.
10
Q
What is the difference between exogenous and endogenous photosensitizers?
A
Exogenous photosensitizers are administered systemically or applied topically, while endogenous photosensitizers are related to cutaneous porphyrias with enzymatic defects in heme biosynthetic pathways.
11
Q
What is the prevalence range of positive responses in patients who had photopatch testing?
A
1.5% to 74%.
12
Q
What are the symptoms of acute phototoxicity?
A
Burning and stinging on exposed areas, erythema, edema, and in severe cases, vesicles and bullae.
13
Q
What is photoonycholysis?
A
Separation of the distal nail from the nail bed, which may be asymptomatic and can manifest as acute phototoxicity.
14
Q
What factors influence acute phototoxicity?
A
It is drug-dose and UV-dose dependent, with symptoms appearing within hours of exposure to the phototoxic agent and UV radiation.
15
Q
What is the role of the nail plate in phototoxicity?
A
The nail plate can serve as a lens to focus UV energy on the nail bed, potentially leading to phototoxic effects.
16
Q
What is the clinical significance of the difference between phototoxicity and photoallergy?
A
Most photosensitivity induced by systemic medications is phototoxicity, while that induced by topical agents is photoallergy.
17
Q
What are the common drugs associated with slate-gray pigmentation on sun-exposed areas?
A
Common drugs include Amiodarone, Chlorpromazine, Clozapine, Imipramine, Desipramine (less common), and Minocycline (can also affect non-sun-exposed areas).
18
Q
What is the most common causative agent of pseudoporphyria?
A
The most common causative agent of pseudoporphyria is Naproxen.
19
Q
What are the chronic effects associated with long-term PUVA treatment?
A
Chronic effects associated with long-term PUVA treatment include premature aging of the skin, lentigines, squamous cell carcinomas, basal cell carcinomas, and melanoma.
20
Q
What is the relationship between voriconazole use and photosensitivity?
A
In immunosuppressed patients receiving voriconazole for longer than 12 weeks, the following effects may occur: photosensitivity, pseudoporphyria, photoaging, lentigines, and premature dermatoheliosis.
21
Q
What are the systemic agents commonly reported to induce photosensitivity?
A
Common systemic agents that induce photosensitivity include Vemurafenib, Voriconazole, Doxycycline, Hydrochlorothiazide, Amiodarone, and Chlorpromazine.
22
Q
What is the likely cause of asymptomatic blue-gray pigmentation on sun-exposed areas after prolonged use of a medication?
A
The condition is slate-gray pigmentation, often caused by drug metabolite-melanin complexes.
23
Q
What is the underlying mechanism for squamous cell carcinoma development in a patient on voriconazole for over a year?
A
Voriconazole can cause accelerated photo-induced changes, leading to photosensitivity, pseudoporphyria, photoaging, lentigines, and premature dermatoheliosis.
24
Q
What is the most common cause of pseudoporphyria with skin fragility and vesicles but normal porphyrin levels?
A
Naproxen is the most common cause.
25
What drugs are likely responsible for photodistributed telangiectasia in a patient on a calcium channel blocker?
Calcium channel blockers like nifedipine, amlodipine, felodipine, and diltiazem can cause photodistributed telangiectasia.
26
What is the likely mechanism for a lichenoid photosensitive eruption after starting doxycycline?
The mechanism involves phototoxicity or photoallergy induced by doxycycline.
27
What drugs are commonly associated with chronic actinic dermatitis?
Drugs like thiazides, quinidine, quinine, and amiodarone are associated with persistent photosensitivity evolving into chronic actinic dermatitis.
28
What is the diagnosis for exaggerated sunburn reactions after starting vemurafenib?
The diagnosis is phototoxicity.
29
What is the action spectrum for vemurafenib-induced phototoxicity?
The action spectrum for vemurafenib-induced phototoxicity is in the UVA range.
30
What are the likely culprits for a burning sensation and erythema on sun-exposed areas after using a topical agent?
Topical agents like fluorouracil, retinoids, and crude coal tar can cause phototoxicity.
31
What are the most commonly reported phototoxic agents after using a systemic medication?
Common agents include vemurafenib, voriconazole, doxycycline, hydrochlorothiazide, amiodarone, and chlorpromazine.
32
What is the typical action spectrum for most phototoxic agents?
The action spectrum for most phototoxic agents is in the UVA range.
33
What is the action spectrum for dyes like porphyrins and fluorescein?
The action spectrum for dyes like porphyrins and fluorescein is in the visible light range.
34
What are common sources of topical furocoumarins?
Common sources include limes, celery, figs, and parsnips.
35
What is the likely diagnosis for a burning sensation after exposure to crude coal tar?
The diagnosis is phototoxicity.
36
What is the mechanism of phototoxic reaction after using systemic fluorouracil?
The mechanism involves direct tissue injury caused by the phototoxic agent and radiation.
37
What are the most common systemic agents involved in phototoxic reactions?
Common agents include vemurafenib, voriconazole, doxycycline, hydrochlorothiazide, amiodarone, and chlorpromazine.
38
What skin condition is associated with chronic exposure to diltiazem?
Photodistributed, reticulated, slate-gray pigmentation.
39
What is the significance of the action spectra in phototoxic agents?
Most action spectra are in the UVA range, except for porphyrins and fluorescein which are in the visible light range.
40
What are the key steps involved in photodynamic processes leading to tissue injury?
1. Absorption of radiation energy by the photosensitizer. 2. Formation of an excited molecule. 3. Generation of reactive oxygen species. 4. Resulting in tissue injury.
41
What are the histopathological findings associated with acute phototoxicity?
- Individual necrotic keratinocytes; if severe, epidermal damage.
- Epidermal spongiosis and dermal edema with mild infiltrate of neutrophils, lymphocytes, and macrophages.
- Slate-gray pigmentation due to increased dermal melanin and drug deposits.
- Lichenoid eruptions similar to idiopathic lichen planus with more spongiosis and necrotic keratinocytes.
42
What management strategies are recommended for acute phototoxicity?
1. Identification and avoidance of the causative phototoxic agent. 2. Rigorous photoprotection: Seek shade, wear photoprotective clothing, wide-brimmed hats, and sunglasses. 3. Use broad-spectrum sunscreens with high SPF. 4. For acute phototoxicity, apply topical corticosteroids and compresses; consider systemic corticosteroids for severe cases.
43
What are the clinical features of photoallergy?
- Sensitized individuals experience pruritic, eczematous eruptions within 24 to 48 hours after exposure.
- Clinically indistinguishable from allergic contact dermatitis.
- Predominantly affects sun-exposed areas, but may spread to covered areas.
- Usually resolves without significant postinflammatory hyperpigmentation.
44
What are the potential long-term effects of UV radiation on photoallergens?
- UV radiation can alter the carrier protein that binds the photoallergen, leading to the formation of a neoantigen.
- This neoantigen can stimulate the immune system over the long term, potentially leading to chronic conditions.
45
What histopathological findings would confirm necrotic keratinocytes after exposure to a phototoxic agent?
Histopathological findings include individual necrotic keratinocytes, epidermal spongiosis, dermal edema, and a mild infiltrate of neutrophils, lymphocytes, and macrophages.
46
What alternative medications can be considered for a patient developing pseudoporphyria after using a nonsteroidal anti-inflammatory drug?
Switch to a different class of agents or less photosensitizing NSAIDs like indomethacin or sulindac.
47
What histopathological findings would support a diagnosis of a lichenoid eruption after exposure to a photosensitizing agent?
Findings include spongiosis, dermal eosinophilic and plasma cell infiltrates, and a larger number of necrotic keratinocytes and cytoid bodies.
48
What condition does dermal-epidermal separation at the lamina lucida indicate after exposure to a phototoxic agent?
This indicates pseudoporphyria, as seen in porphyria cutanea tarda.
49
What is the underlying photodynamic process for a phototoxic reaction with reactive oxygen species formation?
The process involves absorption of radiation energy by the photosensitizer, formation of an excited molecule, and generation of reactive oxygen species leading to tissue injury.
50
What is the mechanism and involved agent for a phototoxic reaction with DNA crosslinking?
The mechanism involves covalent binding of 8-methoxypsoralen to pyrimidine bases of DNA upon UVA exposure, forming crosslinks.
51
What are the key contributors to a phototoxic reaction with inflammatory mediators?
Key contributors include complement activation products, mast cell-derived mediators, eicosanoids, proteases, and polymorphonuclear leukocytes.
52
What is the role of reactive oxygen species in apoptosis after photodynamic therapy?
Reactive oxygen species generated during photodynamic therapy act as potent inducers of apoptosis.
53
What histopathological findings are expected after phototoxicity leading to hyperpigmentation?
Findings include increased dermal melanin and dermal deposits of the drug or its metabolite.
54
What are the key management steps for a phototoxic reaction with erythema and edema?
Key steps include identification and avoidance of the causative agent, rigorous photoprotection, and symptomatic treatment with topical or systemic corticosteroids.
55
What is the expected histopathological finding for a phototoxic reaction with lichenoid eruptions?
Findings include spongiosis, dermal eosinophilic and plasma cell infiltrates, and necrotic keratinocytes.
56
What histopathological findings are expected for pseudoporphyria after using a photosensitizing agent?
Findings include dermal-epidermal separation at the lamina lucida and immunoglobulin deposits at the dermal-epidermal junction.
57
What is the expected histopathological finding in a patient with a phototoxic reaction and lichenoid eruptions?
Findings include spongiosis, dermal eosinophilic and plasma cell infiltrates, and necrotic keratinocytes.
58
What histopathological findings are expected in a patient who develops pseudoporphyria after using a photosensitizing agent?
Findings include dermal-epidermal separation at the lamina lucida and immunoglobulin deposits at the dermal-epidermal junction.
59
What are the photodynamic processes involved in tissue injury?
Absorption of radiation energy by the photosensitizer leads to the formation of an excited molecule and reactive oxygen species, causing tissue injury.
60
What can stable photoproducts induced by radiation exposure cause?
They can be responsible for tissue injury.
61
What is the role of inflammatory mediators in phototoxicity?
They contribute to the development of phototoxicity induced by certain drugs and agents.
62
What is a significant management step for phototoxicity?
Identification and avoidance of the causative phototoxic agent, along with rigorous photoprotection.
63
What is the typical treatment for acute phototoxicity?
Topical corticosteroids and compresses; systemic corticosteroids for severely affected individuals.
64
How does photoallergy present in sensitized individuals?
It presents as a pruritic, eczematous eruption within 24 to 48 hours after exposure.
65
How does UV radiation affect the immune system in relation to photoallergens?
It alters the carrier protein that binds the photoallergen, leading to the formation of a neoantigen that stimulates the immune system over the long term.
66
What are some common topical photoallergens found in the United States and Europe?
UV filters such as benzophenone-3, octocrylene, and avobenzone, as well as topical nonsteroidal anti-inflammatory drugs like ketoprofen.
67
What are the histopathological features associated with phototoxicity?
- Similar to those of **allergic contact dermatitis**.
- **Epidermal spongiosis** associated with infiltrate of **mononuclear cells** in the dermis.
68
What is the pathophysiology of photoallergy?
- It involves a **type IV delayed hypersensitivity response** requiring both photoallergen and UVA radiation.
- The photoallergen is converted to an excited state and may conjugate with a carrier protein to form a complete antigen.
- Mechanisms include:
- **Halogenated salicylamides**, **chlorpromazine**, and **para-aminobenzoic acid**.
- Formation of a stable photoproduct that conjugates with a carrier protein.
- Antigen is processed by **epidermal Langerhans cells** and presented to **T lymphocytes**, leading to cutaneous lesions.
69
What management strategies are recommended for phototoxicity?
- **Identification and avoidance** of the photoallergen.
- Implementation of **sun-protective measures**.
- **Symptomatic therapy** to alleviate symptoms.
70
How can photosensitivity be evaluated in patients?
- Similar to evaluations for other photosensitivity disorders, focusing on:
- **History of exposure** to known photosensitizers.
- Assessing if window glass-filtered sunlight induces cutaneous eruptions.
- **Widespread eruptions** suggest systemic photosensitizers, while localized lesions indicate topical sensitizers.
- **Vesicular and bullous eruptions** are commonly associated with phototoxicity, while **eczematous eruptions** suggest photoallergy.
71
What are the key differences between phototoxicity and photoallergy based on clinical presentation?
| Feature | Phototoxicity | Photoallergy |
|---------|---------------|--------------|
| Sensation | Associated with a **burning sensation** | Associated with **pruritus** |
| Skin Reaction | **Necrotic keratinocytes** commonly seen | **Spongiotic dermatitis** associated |
| Erythema | Well-defined erythema that resolves promptly indicates **irritant dermatitis** | Erythema indicates **photoallergy** or **allergic contact dermatitis** |
72
What does a reaction only at the irradiated site in photopatch testing indicate?
A reaction only at the irradiated site indicates photoallergy.
73
What is the likely diagnosis for a patient with well-defined erythema that resolves promptly after photopatch testing?
The diagnosis is irritant dermatitis.
74
What is the underlying mechanism for spongiotic dermatitis after exposure to a photoallergen?
The mechanism involves a type IV delayed hypersensitivity response, where the photoallergen conjugates with a carrier protein to form a complete antigen, leading to an inflammatory response.
75
What are common photoallergens in the category of topical NSAIDs?
Common photoallergens include ketoprofen and etofenamate.
76
What is the role of Langerhans cells in the process of a pruritic eruption after exposure to a photoallergen?
Langerhans cells take up and process the antigen, migrate to regional lymph nodes, and present the antigen to T lymphocytes, initiating an inflammatory response.
77
What histopathological findings are expected in a patient with chronic actinic dermatitis?
Findings include epidermal spongiosis, dermal edema, and infiltrates of mononuclear cells in the dermis.
78
What is the role of UVA in photopatch testing?
UVA is used as a light source in photopatch testing to activate the photoallergen and assess the reaction.
79
What type of hypersensitivity response is involved in photoallergy?
Type IV delayed hypersensitivity response.
80
What is the mechanism of photoallergy induced by certain drugs?
It involves the absorption of UV light, converting the photoallergen to an excited state molecule that can form a complete antigen.
81
What are the common histopathological features of photoallergy?
Similar to those of allergic contact dermatitis, with epidermal spongiosis and infiltrate of mononuclear cells in the dermis.
82
What management strategies are recommended for photoallergy?
Identification and avoidance of the photoallergen, sun-protective measures, and symptomatic therapy.
83
What does widespread eruption suggest in the evaluation of photosensitivity?
It suggests systemic photosensitizers.
84
What type of eruptions are most commonly associated with phototoxicity?
Vesicular and bullous eruptions.
85
What is the significance of necrotic keratinocytes in phototoxicity?
They are commonly seen in phototoxicity, indicating damage to the skin.
86
What does a reaction only at an irradiated site indicate in photopatch testing?
It indicates photoallergy.
87
What is the role of epidermal Langerhans cells in the mechanism of photoallergy?
They process the antigen and migrate to regional lymph nodes to present it to T lymphocytes.
88
What is the clinical significance of well-defined erythema that resolves promptly in photopatch testing?
It indicates an irritant dermatitis.
89
What are some examples of systemic phototoxic agents classified as antibiotics?
| Common Name (U.S. Trade Name) | Generic Name |
|----------------------------------|--------------|
| Plicamycin | Mithramycin |
| Doxycycline | Vibramycin |
| Minocycline | Minocin |
| Tetracycline | Sumycin |
90
Which class of drugs includes immunosuppressants that can cause phototoxicity?
| Class | Common Name (U.S. Trade Name) | Generic Name |
|-----------------------------------------|--------------------------------|--------------|
| Immunosuppressants, nonsteroidal anti-inflammatory drugs | Acetic acid derivative | Diclofenac |
| | Penicillin | Penicillin |
| | Salicylate | Aspirin |
91
What are some examples of oncologic drugs that can induce phototoxicity?
| Common Name (U.S. Trade Name) | Generic Name |
|----------------------------------|--------------|
| Dactinomycin | Dactinomycin |
| Docetaxel | Taxotere |
| Fluorouracil | Adrucil |
| Methotrexate | Trexall |
92
What are systemic phototoxic agents?
They are drugs that can cause phototoxic reactions when exposed to sunlight.
93
What class of drugs includes Tetracyclines and Sulfonamides?
Antimicrobials.
94
Which class of drugs is known for its immunosuppressive properties?
Immunosuppressants.
95
What is a common side effect of Cardiac drugs like Amiodarone?
Phototoxic reactions.
96
Which class of drugs includes Furosemide and Hydrochlorothiazide?
Diuretics.
97
What type of agents are used in photodynamic therapy?
Photodynamic therapy agents.
98
What is the common name for the drug Doxycycline?
Vibramycin.
99
Which drug is known as a nonsteroidal anti-inflammatory drug (NSAID)?
Ibuprofen.
100
What is the generic name for the drug known as Taxol?
Paclitaxel.
101
What is the common name for the drug Desipramine?
Norpramin.
102
What are some examples of systemic photoallergens and their generic names?
| Property | Generic Name (U.S. Trade Name) |
|----------|-------------------------------|
| Antifungal | Griseofulvin (Fulvicin, Grifulvin G, Gris-PEG) |
| Antimalarial | Quinine |
| Antimicrobials | Quinolone |
| Cardiac medication | Quinine (Quinaglute, Quindex) |
| Nonsteroidal anti-inflammatory drugs | Ketoprofen (Feldene) |
| Vitamin | Pyridoxine hydrochloride (vitamin B6) |
103
What are some common topical photoallergens and their chemical names?
| Group | Chemical Name (Trade Name) |
|-------|----------------------------|
| Sunscreens | Benzophenone-3 (oxybenzone), Benzophenone-4 (sulisobenzone), Para-aminobenzoic acid (PABA) derivatives |
| Fragrances | 6-Methylcoumarin, Musk ambrette, Sandalwood oil |
| Antiinfective agents | Dibromolutehron (DBS), Triclosan (Microban, Lexol 300) |
| Others | Balsam of Peru, Etonamate, Ketoprofen (Invaul gel, Powergel, Tiloket gel) |
104
What are systemic photoallergens and provide an example?
Systemic photoallergens are substances that can cause allergic reactions when exposed to sunlight. An example is Griseofulvin (Fulvicin, Grifulvin, Gris-PEG).
105
What is a common topical photoallergen found in sunscreens?
Benzophenone-3 (oxybenzone) is a common topical photoallergen found in sunscreens.
106
What type of medication is Quinidine classified as in the context of photoallergens?
Quinidine is classified as a cardiac medication that can act as a systemic photoallergen.
107
Name a nonsteroidal anti-inflammatory drug that is a systemic photoallergen.
Ketoprofen is a nonsteroidal anti-inflammatory drug that is a systemic photoallergen.
108
What is the role of PABA derivatives in topical photoallergy?
PABA derivatives, such as Ethylhexyl dimethyl PABA, are used in sunscreens and can act as topical photoallergens.
109
What is a common ingredient in personal care products that can be a photoallergen?
Triclosan is a common ingredient in personal care products that can be a photoallergen.
110
What is the significance of the chemical name 'Octocrylene' in relation to photoallergens?
Octocrylene is a chemical used in sunscreens that can act as a topical photoallergen.
111
What type of agents are salicylanilides and their relevance to photoallergens?
Salicylanilides are antinfective agents that can act as topical photoallergens.
