Antihistamines in Dermatology — MCQs
A patient who experiences recurrent urticaria during exercise and heat exposure, including sunlight, most likely has:
All of the following statements are TRUE about second generation antihistaminic agents EXCEPT:
Second-generation cephalosporin that can be used orally is:
H1 antihistaminic having best topical activity is:
The skin condition shown in the image is associated with?
A patient developed fixed drug eruptions after taking certain medications. Which of the following drugs is known to cause these skin lesions?
Dapsone is used in which of the following conditions?
Which of the following monoclonal antibodies is used in the treatment of atopic dermatitis?
All of the following statements are true regarding warfarin toxicity (skin necrosis) except?
Lichenoid reactions are mainly due to:
Antihistamines in Dermatology Indian Medical PG Practice Questions and MCQs
Question 1: A patient who experiences recurrent urticaria during exercise and heat exposure, including sunlight, most likely has:
- A. Chronic Spontaneous Urticaria
- B. Universal Dermographism
- C. Cholinergic Urticaria (Correct Answer)
- D. Photodermatitis
Explanation: ***Cholinergic Urticaria*** - Cholinergic urticaria is characterized by the appearance of small, itchy wheals in response to stimuli that raise the **body temperature**, such as **exercise**, **heat**, or **emotional stress**. - The symptoms resolve when the body cools down, aligning with the patient's presentation of recurrent urticaria during exercise and heat exposure. *Chronic Spontaneous Urticaria* - This condition involves daily or almost daily urticaria for **six weeks or more** without an identifiable external cause. - While it is chronic, the specific triggers of exercise and heat exposure point more directly to a physical urticaria like cholinergic urticaria. *Universal Dermographism* - **Dermographism** (or dermatographia) is a type of physical urticaria where hives appear after **firm stroking or scratching** of the skin. - Universal dermographism would imply this reaction over a large body surface area, but it is not typically triggered by systemic heat or exercise. *Photodermatitis* - **Photodermatitis** is a general term for skin inflammation caused by **exposure to light**, especially sunlight, often due to an abnormal reaction to UV radiation. - While sunlight is a trigger for this patient's symptoms, the additional triggers of exercise and general heat exposure make cholinergic urticaria a more encompassing diagnosis than photodermatitis alone.
Question 2: All of the following statements are TRUE about second generation antihistaminic agents EXCEPT:
- A. These may possess additional antiallergic mechanisms
- B. These do not impair psychomotor performance
- C. These lack anticholinergic actions
- D. These possess high anti-motion sickness activity (Correct Answer)
Explanation: ***These possess high anti-motion sickness activity*** - Second-generation antihistamines have **poor penetration** into the central nervous system (CNS), making them ineffective for treating **motion sickness**. - **First-generation antihistamines**, which readily cross the blood-brain barrier and have **anticholinergic activity**, are typically used for motion sickness. *These may possess additional antiallergic mechanisms* - Many second-generation antihistamines, such as **cetirizine** and **loratadine**, have additional anti-inflammatory and **antiallergic properties** beyond H1 receptor blockade. - These mechanisms can include inhibiting the release of inflammatory mediators and **stabilizing mast cells**. *These do not impair psychomotor performance* - Second-generation antihistamines are **non-sedating** because they have limited ability to cross the **blood-brain barrier** and thus do not significantly affect CNS function. - This characteristic makes them suitable for use without causing **drowsiness** or impairing activities like driving. *These lack anticholinergic actions* - Unlike first-generation antihistamines, second-generation agents have **minimal to no affinity** for muscarinic acetylcholine receptors. - This lack of **anticholinergic activity** means they do not cause side effects such as **dry mouth**, blurred vision, or urinary retention.
Question 3: Second-generation cephalosporin that can be used orally is:
- A. Cefepime
- B. Cefalothin
- C. Cefaclor (Correct Answer)
- D. Cefadroxil
Explanation: ***Cefaclor*** - **Cefaclor** is a commonly used **second-generation cephalosporin** that is available in an **oral formulation**, making it suitable for outpatient treatment of various bacterial infections. - Its spectrum of activity includes many Gram-positive and Gram-negative bacteria, often used for **respiratory tract infections** and **otitis media**. *Cefepime* - **Cefepime** is a **fourth-generation cephalosporin**, not a second-generation one, and is primarily administered **intravenously** for severe infections. - It has a broader spectrum against both Gram-positive and Gram-negative bacteria, including **Pseudomonas aeruginosa**. *Cefalothin* - **Cefalothin** (also known as cephalothin) is a **first-generation cephalosporin** that is typically administered **parenterally** (intravenously or intramuscularly). - It is not available in an oral formulation, limiting its use to hospital settings for moderate to severe infections. *Cefadroxil* - **Cefadroxil** is a **first-generation cephalosporin** and is available for oral administration. - While it is an oral cephalosporin, it belongs to the first generation, not the second generation as requested by the question.
Question 4: H1 antihistaminic having best topical activity is:
- A. Loratadine
- B. Astemizole
- C. Cetirizine
- D. Azelastine (Correct Answer)
Explanation: **Azelastine (Correct Answer)** - **Azelastine** is an H1 antihistamine available as a **nasal spray** and **eye drops**, demonstrating excellent topical activity. - Its **lipophilicity** and local action make it highly effective for treating allergic rhinitis and conjunctivitis, with minimal systemic absorption. *Loratadine* - **Loratadine** is an oral, second-generation H1 antihistamine primarily used for systemic treatment of allergies. - It does not possess significant topical activity for local application in the nose or eyes. *Astemizole* - **Astemizole** is a second-generation H1 antihistamine that was withdrawn from the market due to significant **cardiac toxicity**, including QTc prolongation and torsades de pointes. - It was an oral medication and did not have widespread topical formulations. *Cetirizine* - **Cetirizine** is an oral H1 antihistamine known for its potency and relatively quick onset of action. - Although it can be used for systemic allergy relief, it is not primarily formulated or recognized for its topical efficacy compared to azelastine.
Question 5: The skin condition shown in the image is associated with?
- A. Diabetes mellitus (Correct Answer)
- B. Hypothyroidism
- C. Hyperthyroidism
- D. Sarcoidosis
Explanation: ***Diabetes mellitus*** - The image shows **diabetic dermopathy** (also known as "shin spots"), which presents as hyperpigmented, atrophic macules or papules, usually on the shins. This condition is a common cutaneous manifestation of **diabetes mellitus**. - Other dermatological conditions associated with diabetes include **necrobiosis lipoidica diabeticorum**, **acanthosis nigricans**, and **erythrasma**, which are important to recognize in patients with diabetes. *Hypothyroidism* - Hypothyroidism is associated with **myxedema**, which typically manifests as non-pitting edema, dry and coarse skin, and hair loss. - While it can cause skin changes, it does not typically present with the pigmented, atrophic lesions seen in the image. *Hyperthyroidism* - Hyperthyroidism can cause skin changes such as **pretibial myxedema** (a specific form of localized skin thickening, typically on the shins, that is often associated with Graves' disease) and warm, moist skin due to increased metabolism. - The lesions shown in the image are not consistent with the typical presentation of pretibial myxedema or other hyperthyroid skin manifestations. *Sarcoidosis* - Sarcoidosis can present with various skin lesions, including **erythema nodosum**, lupus pernio, plaques, and papules. - The skin changes seen in the image, characterized by small, atrophic, hyperpigmented macules, do not fit the typical pattern of cutaneous sarcoidosis.
Question 6: A patient developed fixed drug eruptions after taking certain medications. Which of the following drugs is known to cause these skin lesions?
- A. Phenolphthalein
- B. Aspirin
- C. Dapsone
- D. All of the above (Correct Answer)
Explanation: **Explanation:** **Fixed Drug Eruption (FDE)** is a unique type of cutaneous drug reaction characterized by the recurrence of a lesion (usually a dusky red or violaceous macule) at the **exact same anatomical site** every time the offending drug is ingested. This occurs due to the persistence of **CD8+ memory T-cells** in the basal keratinocytes at the site of the lesion. **Why Option D is correct:** All three drugs listed are classic and high-yield triggers for FDE: * **Phenolphthalein:** Historically the most common cause (found in older laxatives). * **Aspirin (NSAIDs):** A very frequent trigger in clinical practice. * **Dapsone (Sulfonamides):** Sulfonamides are among the most common drug classes associated with FDE. **Analysis of Options:** * **Phenolphthalein:** Often presents as "bullous" FDE. * **Aspirin:** Along with other NSAIDs (like Ibuprofen and Naproxen), it is a leading cause of multi-focal FDE. * **Dapsone:** As a sulfone, it shares cross-reactivity patterns and is a well-documented cause. **High-Yield Clinical Pearls for NEET-PG:** 1. **Most Common Site:** The **glans penis** is the most common site for FDE, followed by the lips and palms. 2. **Commonest Causes (Overall):** NSAIDs, Sulfonamides (Cotrimoxazole), Tetracyclines, and Anticonvulsants. 3. **Clinical Feature:** Lesions often leave behind **post-inflammatory hyperpigmentation (PIH)** after healing. 4. **Refractory Period:** After an eruption, there is a brief refractory period where the drug may not cause a reaction. 5. **Diagnosis:** Primarily clinical; however, a **Patch Test** performed at the site of the previous lesion (not on the back) can confirm the offending agent.
Question 7: Dapsone is used in which of the following conditions?
- A. Dermatitis herpetiformis (Correct Answer)
- B. Pityriasis rosacea
- C. Contact dermatitis
- D. Oculocutaneous albinism
Explanation: **Explanation:** **Dapsone (Diaminodiphenyl sulfone)** is the drug of choice for **Dermatitis Herpetiformis (DH)**. DH is an autoimmune blistering disorder characterized by IgA deposits at the dermal papillae, leading to intense pruritus and neutrophilic infiltration. Dapsone works by inhibiting the enzyme myeloperoxidase and preventing the chemotaxis of neutrophils to the skin, providing rapid symptomatic relief (often within 24–48 hours). **Analysis of Options:** * **A. Dermatitis Herpetiformis:** Correct. It is the primary indication for Dapsone in dermatology. * **B. Pityriasis Rosea:** This is a self-limiting inflammatory condition (likely viral/HHV-6,7). Treatment is supportive (antihistamines, topical steroids); Dapsone has no role. * **C. Contact Dermatitis:** This is a Type IV hypersensitivity reaction. Management involves allergen avoidance and topical or systemic corticosteroids. * **D. Oculocutaneous Albinism:** This is a genetic disorder of melanin synthesis. There is no pharmacological "cure"; management focuses on photoprotection and monitoring for skin cancers. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Antifolate (inhibits dihydropteroate synthase) and anti-inflammatory (inhibits neutrophil recruitment). * **Other Indications:** Leprosy (part of MDT), Pemphigoid, Subcorneal Pustular Dermatosis (Sneddon-Wilkinson disease), and Brown Recluse spider bites. * **Mandatory Pre-screening:** Always check **G6PD levels** before starting Dapsone to prevent severe **hemolytic anemia**. * **Side Effects:** Dose-dependent hemolysis, methemoglobinemia (presents as cyanosis), and the "Dapsone Syndrome" (fever, malaise, exfoliative dermatitis, and hepatitis).
Question 8: Which of the following monoclonal antibodies is used in the treatment of atopic dermatitis?
- A. Ipilimumab
- B. Dupilumab (Correct Answer)
- C. Durvalumab
- D. Reslizumab
Explanation: **Explanation:** **1. Why Dupilumab is Correct:** Dupilumab is a fully human monoclonal antibody that targets the **interleukin-4 receptor alpha (IL-4Rα) subunit**. By binding to this subunit, it inhibits the signaling of both **IL-4 and IL-13**. These cytokines are the key drivers of **Type 2 (Th2) inflammation**, which is the primary pathophysiological mechanism in atopic dermatitis. It is currently the first-line systemic biologic approved for moderate-to-severe atopic dermatitis unresponsive to topical therapies. **2. Why the Other Options are Incorrect:** * **Ipilimumab:** A checkpoint inhibitor that targets **CTLA-4**. It is used in the treatment of advanced melanoma and renal cell carcinoma. * **Durvalumab:** A checkpoint inhibitor that targets **PD-L1**. It is primarily used in the treatment of non-small cell lung cancer (NSCLC) and bladder cancer. * **Reslizumab:** An interleukin-5 (**IL-5**) antagonist. It is used as add-on maintenance treatment for severe eosinophilic asthma, not atopic dermatitis. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Dual inhibitor of IL-4 and IL-13. * **Common Side Effect:** The most characteristic side effect of Dupilumab is **allergic conjunctivitis** and blepharitis. * **Other Indications:** It is also FDA-approved for moderate-to-severe asthma (eosinophilic phenotype) and chronic rhinosinusitis with nasal polyposis. * **Memory Aid:** "Dupi" stops the "D"ermatitis by blocking the "4" and "13" (IL-4/13).
Question 9: All of the following statements are true regarding warfarin toxicity (skin necrosis) except?
- A. Skin necrosis occurs during initiation of therapy.
- B. Most common sites are buttocks and abdomen. (Correct Answer)
- C. Decreased quantity of protein C.
- D. Decreased incidence of adverse effects if therapy with LMWH is started.
Explanation: **Explanation:** Warfarin-induced skin necrosis (WISN) is a rare but severe complication occurring in approximately 0.01% to 0.1% of patients treated with vitamin K antagonists. **Why Option B is the correct answer (The False Statement):** While the buttocks and abdomen are common sites, the **most common sites** for warfarin necrosis are areas with **high subcutaneous fat content**, specifically the **breasts** (in females), followed by the thighs and buttocks. The statement in Option B is considered the "except" because it overlooks the breast as the primary site of predilection. **Analysis of Other Options:** * **Option A:** True. Necrosis typically occurs **3 to 10 days after initiation** of therapy, often due to a large loading dose. * **Option C:** True. Warfarin inhibits Vitamin K-dependent factors (II, VII, IX, X) and anticoagulant proteins (C and S). **Protein C has a shorter half-life** (6 hours) compared to clotting factors. This creates a transient "prothrombotic window" where natural anticoagulants are depleted while procoagulant factors are still active, leading to microvascular thrombosis. * **Option D:** True. Starting **Low Molecular Weight Heparin (LMWH)** as a "bridge" provides immediate anticoagulation, preventing the thrombotic complications during the initial drop in Protein C levels. **Clinical Pearls for NEET-PG:** * **Risk Factor:** Underlying **Protein C deficiency** is the most significant risk factor. * **Clinical Presentation:** Sudden onset of painful, erythematous, or purpuric lesions that rapidly progress to **hemorrhagic bullae and eschar**. * **Management:** Immediate discontinuation of Warfarin, administration of **Vitamin K**, and starting **Heparin** or Protein C concentrates.
Question 10: Lichenoid reactions are mainly due to:
- A. Intake of certain drugs (Correct Answer)
- B. Betel nut chewing
- C. Cigarette smoking
- D. Intake of alcohol
Explanation: **Explanation:** **Lichenoid drug eruptions** (LDE) are cutaneous reactions that clinically and histologically mimic Lichen Planus. The correct answer is **Intake of certain drugs** because LDE is a well-recognized T-cell mediated delayed hypersensitivity reaction triggered by systemic medications. These drugs act as haptens, altering the antigenicity of keratinocytes and leading to a lichenoid tissue reaction characterized by a "saw-tooth" appearance of rete ridges and a band-like lymphocytic infiltrate at the dermo-epidermal junction. **Analysis of Options:** * **A. Intake of certain drugs (Correct):** Common culprits include NSAIDs, Antihypertensives (Beta-blockers, ACE inhibitors, Thiazides), Antimalarials (Chloroquine), and Gold salts. * **B. Betel nut chewing:** This is primarily associated with **Oral Submucous Fibrosis (OSMF)** and squamous cell carcinoma, not lichenoid reactions. * **C. Cigarette smoking:** While smoking is a risk factor for various dermatoses and oral cancers, it is not a primary cause of lichenoid eruptions. Interestingly, smoking is sometimes noted to have a paradoxical (though not therapeutic) inverse relationship with oral lichen planus. * **D. Intake of alcohol:** Alcohol is a trigger for psoriasis and rosacea exacerbations but does not directly cause lichenoid reactions. **High-Yield Clinical Pearls for NEET-PG:** * **Distinguishing LDE from Lichen Planus (LP):** LDE typically lacks **Wickham’s striae**, involves the trunk more than the wrists, and often shows parakeratosis and eosinophils on histology (features usually absent in classic LP). * **Photo-distribution:** Lichenoid drug eruptions often occur in sun-exposed areas (e.g., due to Hydrochlorothiazide). * **Latent Period:** The time between drug intake and eruption can range from weeks to several months.
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