Photoprotection — MCQs
What is the best range of UV light used for treatment of skin diseases?
Chemical peeling is indicated in all of the following except
Which of the following is the platinum-based chemotherapeutic agent used as first-line treatment for ovarian carcinoma?
Which drug is most likely to induce photosensitivity?
Exposure to sunlight can precipitate chronic disc-shaped skin lesions characteristic of which of the following conditions?
A child presents with grouped vesicles on the lips. What is the bedside investigation that you would like to do?
An 8-year-old girl has extreme photosensitivity since birth. She has recently been diagnosed with skin cancer. What is the diagnosis?
Which of the following is NOT a complication of PUVA therapy?
A 12-year-old boy, after spending his holiday on a beach, develops pruritic hemorrhagic vesicles on his cheeks, ears, nose, and hands 12 hours after sun exposure. A week later, the lesions crusted and healed with permanent scars. What is the most probable diagnosis?
Psoralen plus ultraviolet A (PUVA) therapy is useful in which of the following conditions?
Photoprotection Indian Medical PG Practice Questions and MCQs
Question 1: What is the best range of UV light used for treatment of skin diseases?
- A. 100 – 200 nm
- B. > 700 nm
- C. 400 – 700 nm
- D. 200 – 400 nm (Correct Answer)
Explanation: ***200 – 400 nm*** - This range encompasses **UVA (320-400 nm)** and **UVB (290-320 nm)**, which are the most commonly used portions of the **UV spectrum** for treating various skin conditions like psoriasis and eczema. - Specifically, **narrowband UVB (311-313 nm)** is highly effective due to its therapeutic benefits with reduced side effects compared to broadband UVB or UVA. *100 – 200 nm* - This range falls into the **vacuum UV (VUV)** spectrum, which is largely absorbed by air and is not practical for dermatological phototherapy due to its limited penetration and potential for significant cellular damage. - It is known for its germicidal properties but is not used for treating skin diseases in living tissue due to its **high energy** and **low penetration** depth. *> 700 nm* - Wavelengths above 700 nm fall into the **infrared (IR) spectrum** or visible light, which primarily produces heat and has different therapeutic applications. - While IR light can be used for therapies like **pain relief** and **wound healing**, it does not have the immunomodulatory effects on skin cells needed for conditions traditionally treated by UV. *400 – 700 nm* - This range represents the **visible light spectrum**, which is used in some dermatological treatments like **photodynamic therapy (PDT)** or for certain **pigmentary disorders**. - However, visible light does not possess the same **immunomodulatory** and **antiproliferative effects** on keratinocytes and T-cells that make UV light effective for conditions like psoriasis.
Question 2: Chemical peeling is indicated in all of the following except
- A. Melasma
- B. Acne vulgaris
- C. Photoaging
- D. Lichen planus (Correct Answer)
Explanation: ***Lichen planus*** - Chemical peels are generally **contraindicated** in active inflammatory conditions like **lichen planus**, as they can worsen the inflammation or trigger a Koebner phenomenon. - While chemical peels can address post-inflammatory hyperpigmentation, they should not be used during the active phase of lichen planus due to the risk of exacerbation. *Melasma* - **Melasma** is a common indication for chemical peels, particularly superficial and medium-depth peels, to reduce hyperpigmentation. - Peels containing agents like **glycolic acid**, salicylic acid, or trichloroacetic acid are often used to lighten melanin deposits. *Acne vulgaris* - Chemical peels are effective in treating **acne vulgaris** by exfoliating the skin, reducing comedones, and improving overall skin texture. - **Salicylic acid peels** are particularly useful due to their lipophilic nature, allowing them to penetrate and clean pores. *Photoaging* - **Photoaging**, characterized by fine lines, wrinkles, and dyspigmentation from sun exposure, is a primary indication for chemical peels. - Peels can promote **collagen remodeling** and help achieve a more even skin tone and smoother texture.
Question 3: Which of the following is the platinum-based chemotherapeutic agent used as first-line treatment for ovarian carcinoma?
- A. Cyclophosphamide
- B. Methotrexate
- C. Cisplatin (Correct Answer)
- D. Dacarbazine
Explanation: ***Cisplatin*** - **Cisplatin** is a platinum-based chemotherapy drug that forms **DNA cross-links**, inhibiting DNA synthesis and leading to the death of rapidly dividing cells, making it highly effective against **ovarian carcinoma**. - It is a cornerstone of chemotherapy regimens for ovarian cancer, often used in combination with other agents such as paclitaxel. *Methotrexate* - **Methotrexate** is an **antimetabolite** that inhibits dihydrofolate reductase, thereby interfering with DNA synthesis. - While it is used in various cancers like leukemia, lymphoma, and some solid tumors (e.g., breast cancer, gestational trophoblastic disease), it is **not a primary recommended drug for ovarian carcinoma**. *Cyclophosphamide* - **Cyclophosphamide** is an **alkylating agent** that causes DNA damage, leading to cell death. - It is used in many cancers, including lymphoma, breast cancer, and some leukemias, but it is **not a first-line or primary agent for ovarian carcinoma** in contemporary treatment guidelines. *Dacarbazine* - **Dacarbazine** is an **alkylating agent** primarily used in the treatment of **malignant melanoma** and Hodgkin lymphoma. - It is **not indicated for the treatment of ovarian carcinoma**.
Question 4: Which drug is most likely to induce photosensitivity?
- A. Metronidazole
- B. Tetracycline (Correct Answer)
- C. Ivermectin
- D. Fluconazole
Explanation: ***Tetracycline*** - **Tetracyclines** are well-known to cause **photosensitivity reactions**, leading to exaggerated sunburns, rashes, or skin discoloration upon sun exposure. - This adverse effect is thought to be due to an interaction between the drug and UV light, leading to the formation of reactive oxygen species and subsequent cell damage. *Metronidazole* - While metronidazole can cause a variety of side effects, significant **photosensitivity** is generally not considered a common or prominent adverse reaction. - It is often associated with a **disulfiram-like reaction** when consumed with alcohol, as well as gastrointestinal upset and a metallic taste. *Ivermectin* - **Ivermectin** is primarily used as an antiparasitic agent and is not typically associated with **photosensitivity** as a common side effect. - Its main adverse effects are usually related to the Mazzotti reaction during treatment of onchocerciasis or other systemic symptoms like dizziness or nausea. *Fluconazole* - **Fluconazole**, an antifungal medication, has a relatively low incidence of causing **photosensitivity** compared to other drug classes. - Common side effects include gastrointestinal disturbances, headache, and elevated liver enzymes, but severe phototoxic reactions are rare.
Question 5: Exposure to sunlight can precipitate chronic disc-shaped skin lesions characteristic of which of the following conditions?
- A. Dermatitis herpetiformis
- B. Lupus vulgaris
- C. Chloasma
- D. Discoid lupus erythematosus (Correct Answer)
Explanation: ***Discoid lupus erythematosus*** - This condition is a **chronic cutaneous form of lupus** characterized by distinctive **disc-shaped lesions**, often on sun-exposed areas. - **Photosensitivity** is a prominent feature, meaning sunlight direct exposure often **exacerbates or triggers these lesions**. *Chloasma* - This refers to **melasma**, a common condition causing **dark, discolored patches** on the skin, often triggered by **hormonal changes** (e.g., pregnancy) and sun exposure. It does not typically form disc-shaped lesions. - While sunlight exposure influences its presentation, it lacks the characteristic **inflammatory disc-shaped lesions** of discoid lupus. *Dermatitis herpetiformis* - This is an **autoimmune blistering skin condition** strongly associated with **celiac disease**, characterized by intensely pruritic papules and vesicles, not disc-shaped lesions. - Its lesions are **itchy, erythematous papules and vesicles** that are symmetrically distributed, and it is not directly precipitated by sunlight exposure. *Lupus vulgaris* - This is a form of **cutaneous tuberculosis** presenting as slowly progressive, ulcerative, and destructive skin lesions. It is caused by **Mycobacterium tuberculosis** and is unrelated to sun exposure. - It involves direct **tuberculous infection of the skin**, and its clinical presentation differs significantly from the autoimmune, photosensitivity-driven lesions of discoid lupus erythematosus.
Question 6: A child presents with grouped vesicles on the lips. What is the bedside investigation that you would like to do?
- A. Wood's lamp
- B. Slit skin smear
- C. Tzanck smear (Correct Answer)
- D. KOH
Explanation: ***Tzanck smear*** - A **Tzanck smear** is a rapid bedside test that can identify **multinucleated giant cells**, which are seen in herpes simplex virus infections. - The presence of **grouped vesicles on the lips** is highly suggestive of **herpes labialis** (HSV-1), which is primarily a **clinical diagnosis**. - Among the options provided, Tzanck smear is the only relevant bedside investigation, though it has **limited sensitivity and specificity** and **cannot distinguish between HSV and VZV**. - In modern practice, **PCR or direct immunofluorescence** are preferred when laboratory confirmation is needed, but Tzanck smear remains a low-cost option in resource-limited settings. *Wood's lamp* - A Wood's lamp uses **ultraviolet light** to detect certain fungal or bacterial infections by revealing characteristic fluorescence. - It is useful for conditions like **tinea capitis** (green fluorescence) and **erythrasma** (coral-red fluorescence), but has no role in diagnosing viral vesicular lesions. *Slit skin smear* - A **slit skin smear** is used to detect **acid-fast bacilli** in the diagnosis of **leprosy**. - It is not indicated for vesicular lesions and is irrelevant to herpes simplex infection. *KOH* - A **KOH (potassium hydroxide) mount** is used to diagnose **fungal infections** by dissolving keratinocytes and revealing fungal hyphae or spores. - It has no utility in diagnosing viral infections such as herpes simplex.
Question 7: An 8-year-old girl has extreme photosensitivity since birth. She has recently been diagnosed with skin cancer. What is the diagnosis?
- A. Xeroderma Pigmentosum (Correct Answer)
- B. Bloom syndrome
- C. Griscelli syndrome
- D. Chediak Higashi syndrome
Explanation: ***Xeroderma Pigmentosum*** - This condition is characterized by an extreme sensitivity to **ultraviolet (UV) light** from birth due to defects in **DNA repair mechanisms**, leading to severe sunburns, pigmentary changes (freckles, hypopigmented macules), and a high risk of developing **skin cancers** at a young age. - The history of extreme photosensitivity since birth and the diagnosis of skin cancer in an 8-year-old girl is highly indicative of Xeroderma Pigmentosum. *Bloom syndrome* - Bloom syndrome is an inherited disorder characterized by **stunted growth**, a **photosensitive facial rash (telangiectatic erythema)**, and a predisposition to **various cancers**, including leukemia and lymphomas. - While photosensitivity and cancer risk are present, the extreme skin damage and early onset of specific skin cancers (as opposed to leukemias/lymphomas often seen in Bloom) make Xeroderma Pigmentosum a more fitting diagnosis. *Griscelli syndrome* - Griscelli syndrome is a rare autosomal recessive disorder characterized by **partial albinism**, immunodeficiency, and neurological impairment. - While it involves pigmentary abnormalities, it does not typically present with the extreme photosensitivity or the very early skin cancer development described in the patient. *Chediak Higashi syndrome* - Chediak-Higashi syndrome is an autosomal recessive disorder characterized by **partial albinism**, recurrent pyogenic infections, and neurological abnormalities, due to defective lysosomal trafficking. - This syndrome is not primarily associated with extreme photosensitivity leading to early skin cancers but rather with immunodeficiency and neurological issues.
Question 8: Which of the following is NOT a complication of PUVA therapy?
- A. Premature aging of the skin
- B. Cataracts
- C. Skin cancers
- D. Exfoliative dermatitis (Correct Answer)
Explanation: **Explanation:** PUVA (Psoralen + Ultraviolet A) therapy involves the administration of a photosensitizer (8-methoxypsoralen) followed by exposure to UVA radiation. While it is an effective treatment for conditions like psoriasis and vitiligo, it carries specific long-term and short-term risks. **Why Exfoliative Dermatitis is the correct answer:** Exfoliative dermatitis (Erythroderma) is **not** a direct complication of PUVA. In fact, PUVA is often used as a *treatment* modality for certain types of exfoliative dermatitis, such as those caused by Mycosis Fungoides or Psoriasis. While PUVA can cause a "PUVA itch" or a phototoxic burn (erythema), it does not typically trigger generalized exfoliation. **Analysis of Incorrect Options:** * **Premature aging of the skin (Dermatoheliosis):** Chronic UVA exposure leads to the degradation of collagen and elastin fibers, resulting in wrinkles, lentigines, and telangiectasia. * **Cataracts:** Psoralens distribute to the lens of the eye. If the eyes are not protected with UVA-blocking sunglasses for 24 hours post-ingestion, UVA exposure can lead to lens opacification. * **Skin cancers:** PUVA is mutagenic. Long-term therapy significantly increases the risk of Non-Melanoma Skin Cancers (NMSC), particularly **Squamous Cell Carcinoma (SCC)**. **High-Yield Clinical Pearls for NEET-PG:** * **Most common acute side effect:** Erythema (phototoxicity) and pruritus. * **Most common long-term risk:** Squamous Cell Carcinoma (SCC) is more common than Basal Cell Carcinoma (BCC) in PUVA patients (reversing the usual ratio). * **PUVA Lentigines:** Distinctive, irregular pigmented macules that appear after chronic therapy. * **Contraindications:** Pregnancy, lactation, history of skin cancer (Xeroderma Pigmentosum), and severe hepatic/renal failure.
Question 9: A 12-year-old boy, after spending his holiday on a beach, develops pruritic hemorrhagic vesicles on his cheeks, ears, nose, and hands 12 hours after sun exposure. A week later, the lesions crusted and healed with permanent scars. What is the most probable diagnosis?
- A. Polymorphic light eruption
- B. Hydroa vacciniforme (Correct Answer)
- C. Actinic prurigo
- D. Persistent light reaction
Explanation: **Explanation:** The clinical presentation of a young boy with **hemorrhagic vesicles** on sun-exposed areas (cheeks, ears, nose, hands) that heal with **permanent scarring** (varioliform scars) is pathognomonic for **Hydroa vacciniforme (HV)**. **Why Hydroa vacciniforme is correct:** HV is a rare, chronic photodermatosis primarily affecting children. It is triggered by UVA radiation. The hallmark is the progression from erythema to vesicles/bullae, which become umbilicated and hemorrhagic, eventually forming necrotic crusts. The defining feature for NEET-PG is the healing process, which results in **depressed, "vacciniform" (smallpox-like) scars**. It is often associated with **Epstein-Barr Virus (EBV)** infection. **Why other options are incorrect:** * **Polymorphic Light Eruption (PMLE):** The most common photodermatosis. While it causes pruritic papules or vesicles, it **never heals with scarring**. * **Actinic Prurigo:** A variant of PMLE common in Native Americans. It presents with intensely pruritic, excoriated papules and nodules, often involving the lips (cheilitis) and conjunctiva, but does not typically present with hemorrhagic vesicles and varioliform scarring. * **Persistent Light Reaction:** Now classified under Chronic Actinic Dermatitis. It is an eczematous reaction seen in elderly males, where skin remains sensitive to light even without allergen exposure. **High-Yield Clinical Pearls for NEET-PG:** * **Action Spectrum:** UVA is the primary trigger for HV. * **Association:** Severe, systemic cases of HV are linked to **EBV-associated T-cell lymphoproliferative disorders**. * **Differential Diagnosis:** Must be distinguished from Erythropoietic Protoporphyria (EPP), which presents with immediate burning pain and waxy scarring, but lacks the hemorrhagic bullae of HV. * **Management:** Strict photoprotection; severe cases may require antimalarials or immunosuppressants.
Question 10: Psoralen plus ultraviolet A (PUVA) therapy is useful in which of the following conditions?
- A. Vitiligo
- B. Mycosis fungoides
- C. Psoriasis
- D. All of the above (Correct Answer)
Explanation: **Explanation:** **PUVA (Psoralen + UVA)** therapy involves the administration of a photosensitizing agent (8-Methoxypsoralen) followed by exposure to long-wave ultraviolet A light (320–400 nm). The mechanism involves the formation of DNA photo-adducts, which inhibit DNA synthesis and induce apoptosis of hyperproliferating cells and T-lymphocytes. **Why "All of the Above" is Correct:** * **Psoriasis:** PUVA is a classic treatment for moderate-to-severe plaque psoriasis. It reduces the rapid turnover of keratinocytes and suppresses the local cutaneous immune response. * **Vitiligo:** Psoralens stimulate the migration and proliferation of melanocytes from the hair follicle reservoir to the depigmented skin, promoting repigmentation. * **Mycosis Fungoides (MF):** As a cutaneous T-cell lymphoma, MF is highly sensitive to the phototoxic effects of PUVA, which induces apoptosis in malignant T-cells infiltrating the epidermis. **Clinical Pearls for NEET-PG:** 1. **Mechanism:** Psoralens intercalate into DNA; UVA then causes **Type I (oxygen-independent)** reactions forming monoadducts/cross-links and **Type II (oxygen-dependent)** reactions forming free radicals. 2. **Dosage:** Oral psoralen is usually given **0.6 mg/kg**, 2 hours before UVA exposure. 3. **Side Effects:** Acute side effects include nausea and erythema. Long-term risks include **PUVA lentigines** and an increased risk of **Squamous Cell Carcinoma (SCC)**. 4. **Contraindication:** PUVA is contraindicated in patients with Xeroderma Pigmentosum, Lupus Erythematosus, and pregnancy. 5. **Current Trend:** Narrowband UVB (311 nm) has largely replaced PUVA for psoriasis and vitiligo due to a better safety profile, but PUVA remains superior for thick plaques and MF.
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