Scabies — MCQs
Mass Drug Administration is NOT routinely used as the primary strategy for:
All of the following are true regarding Norwegian scabies except
Patient presents with pruritus of the interdigital spaces of the left hand as shown in the image. Identify the condition.
A girl who is staying in a hostel presented with severe itching all over her body for two days. The intense itching worsens at night and after a hot shower. Burrows are seen between the fingers. Approximately how many live mites are there in an adult with scabies?
What is the average number of mites found on the body in a person suffering from regular scabies?
Which of the following statements about scabies is false?
The burrow in scabies is in
Adult scabies is characterized by which of the following?
An 8-month-old child presented with itchy, exudative lesions on the face, palms, and soles. The siblings also have similar complaints. Which of the following is the treatment of choice?
Cutaneous larva migrans is caused by:
Scabies Indian Medical PG Practice Questions and MCQs
Question 1: Mass Drug Administration is NOT routinely used as the primary strategy for:
- A. Vitamin A Deficiency
- B. Scabies (Correct Answer)
- C. Lymphatic Filariasis
- D. Worm infestation
Explanation: ***Scabies*** - While **mass drug administration with oral ivermectin** has shown effectiveness in specific endemic outbreak settings, MDA is generally **not the primary recommended strategy** for routine scabies control in most public health contexts. - Scabies control typically prioritizes **case finding, contact tracing, simultaneous household treatment, and environmental decontamination**—which are more complex to implement than standard MDA programs. - Unlike the other conditions listed, scabies lacks well-established **routine MDA programs** at the scale of national public health initiatives, making it the least suitable option for MDA among these choices. *Vitamin A Deficiency* - **Vitamin A supplementation** through MDA is a **highly effective and widely implemented** WHO-recommended strategy to combat Vitamin A deficiency in at-risk populations, particularly children under 5 years. - Regular mass supplementation helps prevent **xerophthalmia** and reduces morbidity and mortality from infectious diseases. - This is a cornerstone of routine public health programs globally. *Lymphatic Filariasis* - **Lymphatic filariasis** is a classic example where MDA with anti-filarial drugs like **diethylcarbamazine (DEC), albendazole,** or **ivermectin** is the cornerstone strategy for interrupting transmission. - MDA is the **primary WHO-recommended approach** to achieve elimination of lymphatic filariasis, with established national programs in endemic countries. *Worm infestation* - **Mass deworming programs** using drugs like **albendazole** or **mebendazole** represent highly effective and well-established forms of MDA for controlling **soil-transmitted helminth infections**. - These routine programs significantly reduce disease burden in school-aged children, improving nutritional status, growth, and learning outcomes.
Question 2: All of the following are true regarding Norwegian scabies except
- A. Large number of parasites present
- B. Psoriasiform plaques common
- C. Itching is mild or absent
- D. Children commonly affected (Correct Answer)
Explanation: ***Children commonly affected*** - **Norwegian scabies** (also known as **crusted scabies**) primarily affects individuals with **immunocompromise**, **neurological impairment**, or the **elderly**. - While scabies can affect children, the crusted form is **uncommon** in healthy children. *Large number of parasites present* - This statement is true; **crusted scabies** is characterized by an **exceedingly high mite burden**, sometimes numbering in the millions. - The large number of mites leads to the characteristic **crusting and hyperkeratosis**. *Psoriasiform plaques common* - This statement is true; the extensive **hyperkeratosis** and **crusting** in Norwegian scabies often manifest as **thick, scaly plaques** that can resemble **psoriasis**. - These lesions are typically found on the **extremities**, **trunk**, and often involve the **nails** and **scalp**. *Itching is mild or absent* - This statement is true; despite the massive mite load, patients with crusted scabies often experience **surprisingly little or no pruritus**. - This reduced or absent itching is thought to be due to an impaired immune response that also prevents the typical inflammatory reaction to the mites.
Question 3: Patient presents with pruritus of the interdigital spaces of the left hand as shown in the image. Identify the condition.
- A. Sarcoptes scabiei (Correct Answer)
- B. Dermatitis herpetiformis
- C. Xerotic dermatitis
- D. Erythema multiforme
Explanation: ***Sarcoptes scabiei*** - The image shows **papules and excoriations** in the **interdigital spaces**, a classic presentation of **scabies**. Patients typically experience **intense pruritus**, especially at night. - The presence of **burrows**, which are linear or serpiginous tracks, further supports this diagnosis, as these are created by the female mite tunneling into the epidermis. *Dermatitis herpetiformis* - This condition is characterized by **intensely pruritic, symmetrically grouped vesicles and bullae** on extensor surfaces, such as elbows, knees, and buttocks, not primarily interdigital spaces. - It is strongly associated with **celiac disease** and typically responds to a gluten-free diet and dapsone. *Xerotic dermatitis* - **Xerotic dermatitis**, also known as **eczema craquelé** or **winter itch**, is characterized by **dry, fissured skin** that resembles cracked porcelain, often exacerbated by dry weather. - While it causes pruritus, it does not typically present with the papules and burrows seen in scabies, nor is it confined to interdigital spaces in this manner. *Erythema multiforme* - **Erythema multiforme** is an acute, self-limiting inflammatory skin condition characterized by **target lesions** (concentric rings of erythema and edema) and often involves mucous membranes. - It is often triggered by infections (e.g., herpes simplex virus) or drugs and does not primarily present with pruritic papules in interdigital areas.
Question 4: A girl who is staying in a hostel presented with severe itching all over her body for two days. The intense itching worsens at night and after a hot shower. Burrows are seen between the fingers. Approximately how many live mites are there in an adult with scabies?
- A. 20-25
- B. 5-15 (Correct Answer)
- C. 30-50
- D. 25-30
Explanation: ***Approximately 5-15*** - In an adult with typical scabies, the **mite burden is usually low**, with an average of 5-15 live mites. - The intense itching is primarily due to a **hypersensitivity reaction** to the mites and their products, rather than the sheer number of mites. - This is the **characteristic range for classic, uncomplicated scabies** in immunocompetent individuals. *20-25* - This number is generally **higher than the typical mite count** found in classic scabies infestations. - A burden this high might be seen in cases approaching **crusted scabies**, or in prolonged untreated cases. *25-30* - This number is significantly higher than the average mite count for typical scabies. - Such a high burden is characteristic of **crusted (Norwegian) scabies**, a severe form often seen in immunocompromised individuals with widespread crusted lesions. *30-50* - This represents a very high mite burden far exceeding typical scabies. - Such numbers are seen in **crusted (Norwegian) scabies**, which can harbor hundreds to thousands of mites and occurs primarily in immunocompromised patients, elderly, or those with neurological conditions preventing scratching.
Question 5: What is the average number of mites found on the body in a person suffering from regular scabies?
- A. 1 to 5
- B. 15 - 20
- C. 3
- D. 10 to 15 (Correct Answer)
Explanation: ***10 to 15*** - In **classic scabies**, the average number of **Sarcoptes scabiei** mites present on the host's body typically ranges from 10 to 15. - This relatively low number of mites is responsible for the intense **pruritus** and characteristic rash due to the host's immune response to mite antigens and waste products. *1 to 5* - While a very small number of mites might be present in the **early stages** of infestation, an average of 1 to 5 is generally too low for a full-blown symptomatic case of **classic scabies**. - A lower mite count is more typical of **atypical presentations** or infestations in partially treated individuals. *15 - 20* - This range is slightly higher than the typical average reported for **classic scabies**, though still within a reasonable, albeit less common, variation. - A significantly higher number of mites, into the thousands or millions, is characteristic of **crusted (Norwegian) scabies**, a much more severe form of the disease. *3* - Three mites represent a very low burden for a person with **classic scabies**. - Although the total number of mites is often small, an average of three significantly underestimates the typical infestation load that causes widespread itching and rash.
Question 6: Which of the following statements about scabies is false?
- A. Scabies is caused by the mite Sarcoptes scabiei
- B. Not exclusively transmitted sexually.
- C. Erythematous papules develop due to delayed type 4 hypersensitivity.
- D. Pruritus is predominantly absent. (Correct Answer)
Explanation: ***Pruritus is predominantly absent.*** - This statement is false because **pruritus (itching)** is the **hallmark symptom** of scabies and is almost always present, often severe and worse at night. - The intense itching is caused by an **allergic reaction** to the mites, their eggs, and their feces. *Not exclusively transmitted sexually.* - This statement is true; while scabies can be transmitted sexually through **skin-to-skin contact**, it can also spread through **non-sexual close physical contact** with an infected person or contaminated items like bedding. - Transmission requires **prolonged skin-to-skin contact**, not just a brief touch. *Scabies is caused by the mite Sarcoptes scabiei* - This statement is true; the parasitic mite **_Sarcoptes scabiei_ var. _hominis_** is the causative agent of human scabies. - The female mite burrows into the **epidermis** to lay eggs, leading to characteristic lesions and symptoms. *Erythematous papules develop due to delayed type 4 hypersensitivity.* - This statement is true; the **erythematous papules**, vesicles, and intense itching associated with scabies are a result of a **delayed type IV hypersensitivity reaction** to the mite, its feces, and eggs. - The immune response typically develops **3-6 weeks** after primary exposure.
Question 7: The burrow in scabies is in
- A. S. corneum (Correct Answer)
- B. Malpighian layer
- C. S. germinatum
- D. S. granulosum
Explanation: ***S. corneum*** - The **burrow** created by the *Sarcoptes scabiei* mite is specifically found within the **stratum corneum** of the epidermis. - This superficial location allows the mite to feed on **keratinocytes** and deposit eggs, leading to the characteristic rash and intense itching. - The burrow appears as a **serpiginous tract** and is a pathognomonic finding in scabies. *Malpighian layer* - The **Malpighian layer** encompasses the **stratum basale** and **stratum spinosum**, which are deeper layers of the epidermis. - The scabies mite does not burrow into these deeper, metabolically active layers. *S. germinatum* - **Stratum germinativum** is another term for the **stratum basale**, the deepest epidermal layer responsible for cell division. - The scabies mite creates burrows at a much more superficial level in the stratum corneum. *S. granulosum* - The **stratum granulosum** lies between the stratum spinosum and stratum corneum. - While closer to the surface than the Malpighian layer, scabies burrows are specifically located in the more superficial **stratum corneum**, not the granulosum layer.
Question 8: Adult scabies is characterized by which of the following?
- A. Involvement of palms and soles (Correct Answer)
- B. Involvement of the face
- C. Involvement of the anterior abdomen
- D. All of the above
Explanation: **Explanation:** Scabies is a contagious skin infestation caused by the mite *Sarcoptes scabiei var. hominis*. The distribution of lesions is the most critical diagnostic feature in NEET-PG questions. **1. Why Option A is Correct:** In **adult scabies**, the "Circle of Hebra" defines the classic distribution. This includes the interdigital spaces, wrists, elbows, axillae, periumbilical area, and genitalia. While traditionally taught that palms and soles are spared in adults compared to infants, modern clinical dermatology (and standard textbooks like IADVL) recognizes that **palms and soles** are frequently involved in adults, especially in cases of high mite burden or crusted scabies. Among the given options, it is the most characteristic site of involvement. **2. Why Options B and C are Incorrect:** * **Option B (Face):** The face and scalp are characteristically **spared** in adult scabies. This is because adults have a higher density of sebaceous glands; the sebum is thought to be inhibitory to the mites. Facial involvement is a hallmark of **infantile scabies** or **crusted (Norwegian) scabies**. * **Option C (Anterior Abdomen):** While the periumbilical area is involved, "anterior abdomen" is too broad and less specific than the involvement of the palms/soles or the web spaces. **Clinical Pearls for NEET-PG:** * **Infantile Scabies:** Unlike adults, infants show involvement of the **face, scalp, palms, and soles** with common secondary vesicopustules. * **Pathognomonic Sign:** The **Burrow** (a S-shaped track) is the clinical hallmark, most commonly found on the finger webs and wrists. * **Nocturnal Pruritus:** Itching is worst at night due to a Type IV hypersensitivity reaction to the mite, its eggs, and scybala (feces). * **Treatment of Choice:** Topical **Permethrin (5%)** is the gold standard. Oral Ivermectin (200 µg/kg) is an alternative or adjunct for crusted scabies.
Question 9: An 8-month-old child presented with itchy, exudative lesions on the face, palms, and soles. The siblings also have similar complaints. Which of the following is the treatment of choice?
- A. Systemic ampicillin
- B. Topical permethrin (Correct Answer)
- C. Systemic prednisolone
- D. Topical betamethasone
Explanation: ### Explanation **Diagnosis: Infantile Scabies** The clinical presentation of itchy, exudative lesions involving the **palms and soles**, combined with a **positive family history** (siblings affected), is pathognomonic for Scabies. In infants, unlike adults, the lesions frequently involve the face, scalp, palms, and soles and often present as vesicles or pustules due to secondary eczematization. **1. Why Topical Permethrin is Correct:** * **Permethrin (5% cream)** is the **drug of choice** for scabies in infants older than 2 months. * **Mechanism:** It acts by disrupting the sodium channel currents in the neurons of the *Sarcoptes scabiei* mite, leading to paralysis and death. * **Application:** It should be applied from head to toe in infants (including the face and scalp, avoiding eyes/mouth) and washed off after 8–12 hours. **2. Why Other Options are Incorrect:** * **Systemic Ampicillin:** While lesions may appear "exudative" due to secondary bacterial infection (impetiginization), the primary pathology is parasitic. Antibiotics alone will not cure the underlying infestation. * **Systemic Prednisolone & Topical Betamethasone:** These are corticosteroids. Using steroids in scabies is contraindicated as they mask the symptoms ("Scabies Incognito") and can worsen the infestation by suppressing the local immune response against the mites. **3. NEET-PG High-Yield Pearls:** * **Drug of Choice in Pregnancy/Lactation:** Permethrin 5%. * **Ivermectin:** Oral ivermectin (200 µg/kg) is an alternative but is generally **avoided in children weighing <15 kg** or pregnant women. * **Nodular Scabies:** Characterized by reddish-brown itchy nodules in the axilla and genitalia; treated with intralesional steroids. * **Crusted (Norwegian) Scabies:** Seen in immunocompromised patients; characterized by thousands of mites and minimal itching. Requires combination therapy (Oral Ivermectin + Topical Permethrin). * **Key Management Rule:** Always treat all close contacts simultaneously, even if asymptomatic, to prevent re-infestation.
Question 10: Cutaneous larva migrans is caused by:
- A. A. braziliense (Correct Answer)
- B. Toxocara canis
- C. Strongyloides
- D. Necator americanus
Explanation: **Explanation:** **Cutaneous Larva Migrans (CLM)**, also known as "creeping eruption," is a zoonotic infestation caused by the larvae of animal hookworms. 1. **Why A is correct:** The most common causative agent is **Ancylostoma braziliense** (the hookworm of cats and dogs). Humans are accidental "dead-end" hosts. When larvae from soil contaminated with animal feces penetrate human skin, they lack the enzymes necessary to penetrate the basement membrane and enter the circulation. Consequently, they remain confined to the epidermis, migrating aimlessly and creating the characteristic **serpiginous, erythematous, pruritic tracks**. 2. **Why the other options are incorrect:** * **Toxocara canis:** Causes **Visceral Larva Migrans (VLM)** or Ocular Larva Migrans. The larvae migrate through internal organs rather than the skin. * **Strongyloides stercoralis:** Causes **Larva Currens**. This is distinguished by its extreme speed of migration (up to 5–10 cm/hour) and typically starts near the perianal region. * **Necator americanus:** This is a human hookworm. Unlike animal hookworms, it can penetrate the dermis and enter the bloodstream to complete its life cycle, causing systemic hookworm disease rather than localized CLM. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site:** Feet (due to walking barefoot on beaches or moist soil). * **Rate of migration:** 1–2 cm per day (much slower than Larva Currens). * **Löffler’s Syndrome:** Can rarely occur if larvae reach the lungs (transient pulmonary infiltrates with eosinophilia). * **Treatment of choice:** **Albendazole** (400 mg for 3–5 days) or a single dose of **Ivermectin** (200 μg/kg). Topical Thiabendazole is also an option.
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