Sunscreens and Photoprotective Agents — MCQs
Which of the following substances can lead to fixed drug eruptions?
In which of the following conditions is phototherapy, specifically ultraviolet light therapy, useful for treatment?
Which type of ultraviolet radiation causes the most skin disorders?
Which of the following is an example of a barrier method of contraception?
Assertion: Vitamin D analogues are effective in psoriasis. Reason: They reduce keratinocyte proliferation
Which of the following is not a component of sebum?
Addition of which Amino Acid will increase UV absorption
What is the first-line treatment for melasma?
In the context of filtration, what type of filter is a Seitz filter?
Ichthyosis is a side effect of -
Sunscreens and Photoprotective Agents Indian Medical PG Practice Questions and MCQs
Question 1: Which of the following substances can lead to fixed drug eruptions?
- A. Na fluorititanate
- B. Phenolphthalein (Correct Answer)
- C. Magnesium oxide
- D. CaSO4
Explanation: ***Phenolphthalein*** - **Phenolphthalein** is a common cause of fixed drug eruptions, often found in laxatives. - Exposure to the drug can cause recurrent, well-demarcated skin lesions in the exact same location each time it is ingested [1]. *Na fluorititanate* - This compound is not commonly associated with causing fixed drug eruptions. - It is primarily used in industrial applications, such as ceramics and enamels. *Magnesium oxide* - **Magnesium oxide** is a common antacid and laxative, but it is rarely implicated in fixed drug eruptions. - Its adverse effects usually involve gastrointestinal symptoms rather than cutaneous reactions. *CaSO4* - **Calcium sulfate (CaSO4)**, or gypsum, is primarily used in construction and as a filler in pharmaceuticals. - It is not recognized as a common causative agent for fixed drug eruptions.
Question 2: In which of the following conditions is phototherapy, specifically ultraviolet light therapy, useful for treatment?
- A. Psoriasis (Correct Answer)
- B. Tinea corporis
- C. Pemphigus
- D. PMLE
Explanation: ***Psoriasis*** - **Phototherapy** (narrowband UVB, broadband UVB, or PUVA) is a **well-established first-line treatment** for **moderate-to-severe psoriasis**. - It works by **suppressing overactive immune cells** in the skin, reducing inflammation and decreasing keratinocyte proliferation. - **Direct therapeutic effect** on active psoriatic lesions makes this the primary indication for phototherapy in dermatology. *Tinea corporis* - **Tinea corporis** is a **superficial fungal infection** (dermatophytosis) of the skin. - Requires **antifungal medications** (topical azoles or oral terbinafine/griseofulvin) for treatment. - **Phototherapy has no antifungal activity** and is not used for this condition. *Pemphigus* - **Pemphigus** is an **autoimmune blistering disease** with intraepidermal acantholysis. - Treatment requires **systemic immunosuppression** (corticosteroids, rituximab, azathioprine). - **Phototherapy is not indicated** and could potentially worsen the condition. *PMLE* - **Polymorphous light eruption (PMLE)** is a common **photosensitivity disorder**. - While **prophylactic photohardening** (gradual controlled UV exposure) can be used to build tolerance **before sun exposure season**, this is a **preventative desensitization strategy**, not treatment of active disease. - Unlike psoriasis, phototherapy does **not treat active PMLE lesions** and can trigger flares if not done properly. - The primary approach for active PMLE is **sun avoidance, sun protection, and topical corticosteroids**.
Question 3: Which type of ultraviolet radiation causes the most skin disorders?
- A. UV-A
- B. UV-B (Correct Answer)
- C. UV-C
- D. None of the options
Explanation: ***UV-B*** - **UV-B radiation** is a major cause of **sunburn** and directly damages DNA, leading to most **skin cancers** (basal cell carcinoma, squamous cell carcinoma, and melanoma). - It plays a significant role in photoaging and the development of most **skin disorders** related to sun exposure. *UV-A* - **UV-A radiation** penetrates deeper into the skin than UV-B and is primarily associated with **photoaging**, producing wrinkles and fine lines. - While it contributes to skin cancer development, its direct role in DNA damage and sunburn is less than that of UV-B. *UV-C* - **UV-C radiation** is the most damaging type of UV light, but it is almost entirely **absorbed by the Earth's ozone layer** and does not reach the Earth's surface. - Therefore, it does not typically cause skin disorders in humans under natural conditions. *None of the options* - This option is incorrect because **UV-B radiation** is well-established as a primary cause of numerous skin disorders, including most skin cancers and sunburn.
Question 4: Which of the following is an example of a barrier method of contraception?
- A. Hormonal contraceptive
- B. IUD
- C. Condom (Correct Answer)
- D. Sterilization
Explanation: ***Condom*** - A **condom** acts as a physical barrier, preventing sperm from reaching the egg. - Both male and female condoms are examples of **barrier contraception**. *Hormonal contraceptive* - **Hormonal contraceptives** work by preventing ovulation, thickening cervical mucus, or altering the uterine lining, not by physically blocking sperm. - Examples include oral contraceptive pills, patches, and vaginal rings. *IUD* - An **intrauterine device (IUD)**, whether hormonal or copper, primarily prevents conception by creating an inhospitable environment for sperm or by preventing implantation. - It is a long-acting reversible contraceptive, not a barrier method. *Sterilization* - **Sterilization** (e.g., tubal ligation or vasectomy) is a permanent method of contraception that prevents the transport of eggs or sperm, respectively. - It does not involve a physical barrier to block sperm during intercourse.
Question 5: Assertion: Vitamin D analogues are effective in psoriasis. Reason: They reduce keratinocyte proliferation
- A. Both A & R true, R explains A (Correct Answer)
- B. A false R true
- C. Both A & R true, R doesn't explain A
- D. A true R false
Explanation: ***Both A & R true, R explains A*** - **Vitamin D analogues** (e.g., calcipotriol) are a cornerstone treatment for psoriasis because they effectively modulate **keratinocyte proliferation** and differentiation. - Psoriasis is characterized by the **rapid overgrowth of keratinocytes**, and the antiproliferative effects of vitamin D analogues directly address this pathological hallmark. *A false R true* - This option is incorrect because both the assertion (Vitamin D analogues are effective in psoriasis) and the reason (They reduce keratinocyte proliferation) are individually true. - The effectiveness of vitamin D analogues in treating psoriasis is well-established in dermatological practice. *Both A & R true, R doesn't explain A* - This option is incorrect because the reduction of keratinocyte proliferation is precisely *how* vitamin D analogues exert their therapeutic effect in psoriasis. - The mechanism of action described in the reason directly explains the efficacy mentioned in the assertion. *A true R false* - This option is incorrect because the reason ("They reduce keratinocyte proliferation") is a fundamental and well-understood mechanism by which vitamin D analogues work in psoriasis. - Vitamin D analogues bind to vitamin D receptors in keratinocytes, influencing gene expression to inhibit their excessive growth.
Question 6: Which of the following is not a component of sebum?
- A. Wax
- B. Glycerides
- C. Propylene (Correct Answer)
- D. Cholesterol
Explanation: ***Propylene*** - **Propylene** (or polypropylene) is a synthetic polymer used in plastics and fibers, not a naturally occurring component of human sebum. - Sebum is a complex mixture of lipids produced by the sebaceous glands to lubricate the skin and hair. *Wax* - **Waxes** (specifically wax esters) are a significant component of sebum, contributing to its protective and hydrophobic properties. - These esters are formed from fatty acids and long-chain alcohols. *Glycerides* - **Glycerides**, particularly triglycerides (esters of glycerol and fatty acids), are major components of sebum, making up a large percentage of its total lipid content. - They contribute to the skin's lipid barrier and emollient properties. *Cholesterol* - **Cholesterol** and its esters are also present in sebum, playing a role in maintaining the integrity and fluidity of the skin barrier. - It works alongside other lipids to prevent water loss and protect against external factors.
Question 7: Addition of which Amino Acid will increase UV absorption
- A. Tryptophan (Correct Answer)
- B. Leucine
- C. Proline
- D. Arginine
Explanation: ***Tryptophan*** - **Tryptophan** contains an **indole ring** with a conjugated pi system responsible for strong **UV light absorption** at approximately **280 nm**. - Its unique aromatic structure allows it to absorb UV light, making it a key amino acid for protein quantification using **spectrophotometry**. *Leucine* - **Leucine** is an **aliphatic amino acid** with a non-polar side chain and lacks chromophores. - It does not significantly absorb UV light in the typical range used for protein analysis. *Proline* - **Proline** is an **imino acid** with a unique cyclic structure, but it lacks aromatic rings or conjugated double bonds. - It does not absorb UV light significantly at wavelengths above 230 nm. *Arginine* - **Arginine** is a **basic amino acid** with a guanidinium group, but this functional group does not contribute to UV absorption in the 280 nm range. - Its presence does not enhance the UV absorbance of proteins.
Question 8: What is the first-line treatment for melasma?
- A. Laser therapy
- B. Topical hydroquinone (Correct Answer)
- C. Chemical peels
- D. Microdermabrasion
Explanation: ***Topical hydroquinone*** - **Topical hydroquinone** (2-4%) is the **most effective single-agent treatment** among the given options, serving as the gold standard for melasma by inhibiting **tyrosinase enzyme** and melanin production. - Demonstrates **highest efficacy rates** (60-80% improvement) when combined with strict sun protection, making it both first-line and most effective monotherapy choice. *Laser therapy* - Carries **high risk of paradoxical darkening** and post-inflammatory hyperpigmentation, especially in darker skin types common in melasma patients. - Requires **specialized expertise** and should only be considered as adjunctive therapy after optimizing topical treatments, not as primary treatment. *Chemical peels* - Provide **variable and inconsistent results** as monotherapy, typically requiring multiple sessions with unpredictable outcomes. - Risk of **post-inflammatory hyperpigmentation** particularly in Fitzpatrick skin types IV-VI, making them less reliable than hydroquinone. *Microdermabrasion* - Offers only **superficial exfoliation** with minimal clinical improvement in melasma pigmentation. - May actually **worsen pigmentation** through mechanical irritation and is not recommended in evidence-based treatment guidelines.
Question 9: In the context of filtration, what type of filter is a Seitz filter?
- A. Depth filter (Correct Answer)
- B. Candle filter
- C. Membrane filter
- D. Sintered glass filter
Explanation: ***Depth filter*** - A **Seitz filter** is a classic example of a **depth filter**, which works by trapping particles within a thick matrix of fibrous material. - Its mechanism involves both **adsorption** and **mechanical retention** as fluid passes through the tortuous path of the filter medium. *Candle filter* - **Candle filters**, such as ceramic filters, are generally **surface filters** that retain particles on their outer surface. - They are often used for larger particle removal and can be cleaned more easily than depth filters. *Membrane filter* - **Membrane filters** operate primarily as **surface filters** with very precise pore sizes, providing absolute filtration efficiency for submicron particles. - They are typically made from polymeric materials and are used for sterile filtration and precise particle separation. *Sintered glass filter* - **Sintered glass filters** are made by fusing glass particles to create a porous structure used primarily in **laboratory settings** for chemical filtration. - While they can act as a depth filter, they are distinct from the industrial-scale fibrous depth filters like the Seitz filter.
Question 10: Ichthyosis is a side effect of -
- A. Capreomycin
- B. Letrozole
- C. Clofazimine (Correct Answer)
- D. Cephalosporin
Explanation: ***Clofazamine*** - **Clofazimine** is an antimycobacterial drug used to treat **leprosy**, and one of its characteristic skin-related side effects is **ichthyosis**, presenting as dry, scaly skin. - It accumulates in fatty tissues and the reticuloendothelial system, causing a range of skin pigmentation changes from red-brown to black, often associated with generalized dryness and scaling. *Capreomycin* - **Capreomycin** is an injectable antibiotic primarily used for **multi-drug resistant tuberculosis (MDR-TB)**. - Its main side effects involve **nephrotoxicity** and **ototoxicity**, not ichthyosis. *Letrozole* - **Letrozole** is an **aromatase inhibitor** used in the treatment of **hormone-receptor-positive breast cancer** in postmenopausal women. - Common side effects include **hot flashes**, **arthralgia**, and **fatigue**, but not ichthyosis. *Cephalosporin* - **Cephalosporins** are a class of **beta-lactam antibiotics** widely used for bacterial infections. - While they can cause various side effects like **allergic reactions** (rash, anaphylaxis), **gastrointestinal upset**, and **nephrotoxicity** at high doses, ichthyosis is not a recognized side effect.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free