Antiparasitic Therapy — MCQs
Scabies oral treatment of choice:
Ivermectin is indicated in the treatment of:
All of the following are true about nasal myiasis except which of the following?
A 42-year-old Bengali male presents with painless nodules over the face. The face is erythematous, and the surface of some of the large nodules is discolored. He gives a history of an insect bite in the past while he went to the jungle for work. What is the most likely diagnosis?
The burrow in scabies is in
Which of the following statements is not correct regarding sebaceous cyst?
The skin condition shown in the image is associated with?
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:
Antiparasitic Therapy Indian Medical PG Practice Questions and MCQs
Question 1: Scabies oral treatment of choice:
- A. Benzyl Benzoate
- B. Ivermectin (Correct Answer)
- C. Lindane
- D. Permethrin
Explanation: ***Ivermectin*** - **Ivermectin** is the **oral treatment of choice** for scabies, especially in cases of crusted (Norwegian) scabies, immunocompromised patients, or when topical treatments fail. - It works by disrupting the **neurotransmitter system** of parasites, leading to paralysis and death of the scabies mites. *Benzyl Benzoate* - **Benzyl benzoate** is a **topical scabicide** and acaricide, used as a lotion or emulsion. - It is not available as an oral formulation and is typically reserved for cases where other topical agents are ineffective or contraindicated. *Lindane* - **Lindane** (gamma-hexachlorocyclohexane) is a topical scabicide but is **not recommended as a first-line treatment** due to potential **neurotoxicity** (seizures) especially in infants, children, and individuals with extensive skin excoriations. - It is used topically and has significant systemic absorption, making its use limited. *Permethrin* - **Permethrin** cream is considered the **first-line topical treatment** for scabies, showing high efficacy and a good safety profile. - It is not an oral medication; it is applied topically to the skin to kill mites.
Question 2: Ivermectin is indicated in the treatment of:
- A. Scabies (Correct Answer)
- B. Dermatophytosis
- C. Tuberculosis
- D. Syphilis
Explanation: ***Scabies*** - **Ivermectin** is an effective oral antiparasitic agent used to treat **scabies**, particularly in cases of widespread infestation, crusted scabies, or when topical treatments fail. - It acts by paralyzing and killing the **Sarcoptes scabiei mites** responsible for the infestation. *Dermatophytosis* - **Dermatophytosis** (ringworm) is a **fungal infection** of the skin, hair, or nails. - It is typically treated with **antifungal medications** (e.g., azoles, terbinafine), not ivermectin. *Tuberculosis* - **Tuberculosis** is a bacterial infection caused by **Mycobacterium tuberculosis**, primarily affecting the lungs. - Treatment involves a multi-drug regimen of **antibiotics** (e.g., rifampin, isoniazid), for several months. *Syphilis* - **Syphilis** is a sexually transmitted bacterial infection caused by **Treponema pallidum**. - The primary treatment for syphilis is **penicillin**, usually administered via injection.
Question 3: All of the following are true about nasal myiasis except which of the following?
- A. Common in vasomotor rhinitis
- B. Nasal myiasis can cause intense nasal irritation.
- C. Meningitis may occur in severe nasal myiasis.
- D. Nasal myiasis is typically asymptomatic (Correct Answer)
Explanation: ***Nasal myiasis is typically asymptomatic*** - This statement is **INCORRECT** and is the correct answer to this "except" question. - **Nasal myiasis** is characterized by infestation of the nasal cavity with **fly larvae (maggots)**, which typically causes **significant symptoms** rather than being asymptomatic. - Patients usually experience **nasal obstruction**, **epistaxis (nosebleeds)**, **foul-smelling nasal discharge**, **intense irritation**, and a sensation of movement in the nose due to the feeding and movement of the larvae. - The condition is rarely asymptomatic and usually prompts patients to seek medical attention due to the distressing symptoms. *Common in vasomotor rhinitis* - This statement is **INCORRECT** as a factual claim about myiasis. Nasal myiasis is **NOT** commonly associated with vasomotor rhinitis. - Nasal myiasis is more commonly associated with **atrophic rhinitis**, **ozena**, neglected nasal wounds, poor hygiene, open mouth breathing during sleep, and immunosuppression. - **Vasomotor rhinitis** is a non-allergic condition characterized by fluctuating nasal congestion, rhinorrhea, and sneezing, without any direct association with parasitic infestations. - However, this option may cause confusion as it could also be considered false. The most clearly false statement is that myiasis is "typically asymptomatic." *Nasal myiasis can cause intense nasal irritation* - This statement is **TRUE**. The presence and movement of **maggots** within the nasal cavity leads to severe **irritation**, pain, and a foreign body sensation. - The feeding activity of the larvae causes **tissue destruction**, mucosal damage, and secondary bacterial infections, intensifying discomfort. - Patients often describe a crawling sensation and severe itching in the nasal cavity. *Meningitis may occur in severe nasal myiasis* - This statement is **TRUE**. In advanced or neglected cases, the **larvae** can erode through the nasal structures, sinuses, and skull base, potentially breaching the **meninges**. - This invasion can result in serious intracranial complications such as **meningitis**, **brain abscess**, **cavernous sinus thrombosis**, or other central nervous system infections. - These complications are life-threatening and require urgent surgical debridement and antimicrobial therapy.
Question 4: A 42-year-old Bengali male presents with painless nodules over the face. The face is erythematous, and the surface of some of the large nodules is discolored. He gives a history of an insect bite in the past while he went to the jungle for work. What is the most likely diagnosis?
- A. Chronic Fungal infections
- B. Cutaneous Leishmaniasis (Correct Answer)
- C. Cutaneous tuberculosis
- D. Leprosy
Explanation: ***Cutaneous Leishmaniasis*** - The presentation of **painless erythematous nodules** on the face, especially in a person with a history of **insect bites** and exposure to a **jungle environment** (where sandflies, vectors of Leishmania, are common), strongly suggests cutaneous leishmaniasis. - The discoloration of the surface of large nodules is also consistent with the typical appearance of **chronic cutaneous leishmaniasis lesions**. *Chronic Fungal infections* - While chronic fungal infections can cause skin nodules, they typically present with features like **scaling, itching, or satellite lesions**, which are not described here. - The specific history of **insect bites** and geographical context points away from common fungal etiologies. *Cutaneous tuberculosis* - Cutaneous tuberculosis can manifest as nodules (**lupus vulgaris** or **scrofuloderma**), but these are often associated with other signs of tuberculosis, such as **pulmonary involvement** or **lymph nodal enlargement**, and typically have a slower progression. - The history of **insect bite** is not a primary risk factor for cutaneous tuberculosis. *Leprosy* - Leprosy, particularly **lepromatous leprosy**, can cause extensive facial nodules, but these are often associated with **nerve involvement** leading to sensory loss, and the lesions tend to be diffusely infiltrative rather than discrete, discolored nodules. - The rapid onset or history of a single insect bite is less characteristic of leprosy, which has a very **long incubation period**.
Question 5: 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 6: Which of the following statements is not correct regarding sebaceous cyst?
- A. Found on hairy areas of the body
- B. Treatment is incision and drainage (Correct Answer)
- C. Not found on palms and soles
- D. It has a punctum
Explanation: ***Treatment is incision and drainage*** - The standard treatment for a sebaceous cyst (more accurately an **epidermoid cyst** or **pilar cyst**) is **surgical excision** of the entire cyst wall to prevent recurrence. - **Incision and drainage** only provides temporary relief by emptying the contents but leaves the cyst wall intact, leading to a high chance of the cyst refilling. *Found on hairy areas of the body* - This statement is generally correct as sebaceous cysts often arise from hair follicles and are common in **hair-bearing areas** like the scalp, face, neck, and trunk. - They occur due to the accumulation of **sebum** and keratin within a blocked or damaged sebaceous gland or hair follicle. *Not found on palms and soles* - This statement is correct because **palms and soles** generally **lack sebaceous glands** and hair follicles, hence sebaceous cysts are typically not found in these locations. - Cysts found in these areas are more likely to be **ganglion cysts** or other types of epidermal inclusion cysts. *It has a punctum* - This statement is often correct; many sebaceous cysts (especially epidermoid cysts) have a visible **central punctum** which represents the occluded pore from which the cyst originated. - This punctum is a **key diagnostic feature** and can sometimes exude a cheesy, foul-smelling material.
Question 7: 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 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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