Drugs for Parasitic Skin Infestations — MCQs
Which of the following statements about scabies is false?
Which of the following is NOT used in scabies?
Mass Drug Administration is NOT routinely used as the primary strategy for:
All of the following are part of the treatment of scabies except?
Mass Drug Administration is not helpful for:
A 45 year old female presents with the complaint of pain in the metacarpophalangeal, proximal interphalangeal and metatarsophalangeal joints of both right and left hands. Serology showed positive anti-CCP antibodies. She was placed on infliximab for control. Which of the following need to tested before starting treatment?
A 45-year-old male having a long history of cigarette smoking presented with gangrene of the left foot, which was treated with an amputation. Representative sections from the specimen revealed the presence of arterial thrombus with neutrophilic infiltrate in the arterial wall, as well as inflammation extending into the adjacent veins and nerves. What is the most probable diagnosis?
What is the drug of choice for treating isosporiasis?
23 years old woman complains of recurrent acne over her face. History revealed that she had taken topical antibiotics for her acne without any significant improvement. Which one of the following tetracyclines is most preferred for her acne?
Most reliable indicator of some dehydration?
Drugs for Parasitic Skin Infestations Indian Medical PG Practice Questions and MCQs
Question 1: 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 2: Which of the following is NOT used in scabies?
- A. Ciclopirox oleamine (Correct Answer)
- B. BHC
- C. Permethrin
- D. Crotamiton
Explanation: ***Ciclopirox oleamine*** - **Ciclopirox oleamine** is an **antifungal agent** primarily used to treat cutaneous fungal infections like tinea infections and onychomycosis. - It has no known activity against **Sarcoptes scabiei** mites and is therefore not used in the treatment of scabies. *BHC* - **Benzene hexachloride (BHC)**, specifically gamma-benzene hexachloride or **lindane**, is an older scabicide that has been used to treat scabies. - Due to concerns about **neurotoxicity and resistance**, its use has become more restricted, but it was historically a common treatment for scabies. *Permethrin* - **Permethrin cream (5%)** is considered the **first-line treatment** for scabies due to its efficacy and safety profile. - It is a **synthetic pyrethroid** that acts as a neurotoxin to the scabies mite. *Crotamiton* - **Crotamiton (10%) cream or lotion** is used as a scabicide and also has **antipruritic properties**, providing relief from itching. - While less effective than permethrin, it is an alternative for patients who cannot tolerate other treatments or when other treatments are contraindicated.
Question 3: 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 4: All of the following are part of the treatment of scabies except?
- A. Topical Permethrin
- B. Oral antihistamines
- C. Oral ivermectin
- D. Long term oral steroids (Correct Answer)
Explanation: ***Long term oral steroids*** - **Long-term oral steroids** are generally avoided in scabies treatment as they can **suppress the immune system**, potentially worsening the infestation. - While steroids might offer temporary relief from itching, they do not address the underlying parasitic cause and can lead to various **side effects** with prolonged use. *Topical Permethrin* - **Topical permethrin** 5% cream is a **first-line treatment** for scabies, highly effective against the *Sarcoptes scabiei* mite. - It is typically applied to the entire body from the neck down, left on for 8-14 hours, and then washed off. *Oral ivermectin* - **Oral ivermectin** is an alternative treatment, particularly useful for **crusted scabies**, widespread infestations, or in cases where topical treatments are difficult to administer. - It acts by disrupting the nervous system of the mites, leading to their death. *Oral antihistamines* - **Oral antihistamines** are used to manage the **intense pruritus** (itching) associated with scabies. - They do not kill the mites but provide symptomatic relief, improving patient comfort.
Question 5: Mass Drug Administration is not helpful for:
- A. Lymphatic Filariasis
- B. Vitamin A Deficiency
- C. Worm infestation
- D. Scabies (Correct Answer)
Explanation: ***Scabies*** - **Mass Drug Administration (MDA)** for scabies is primarily an emergency intervention in high-prevalence settings, but it's generally not a sustainable or long-term solution for control due to high re-infection rates and the need for concomitant treatment of household contacts and environmental measures. - **Ivermectin** MDA can be effective in reducing prevalence in some communities, but it often needs to be combined with other strategies due to the risk of drug resistance and the importance of topical treatments, hygiene, and environmental sanitation. *Lymphatic Filariasis* - **MDA with anti-filarial drugs** (e.g., albendazole, ivermectin, diethylcarbamazine citrate) is a cornerstone of global **lymphatic filariasis elimination programs**. - It aims to reduce microfilariae in the blood to interrupt transmission by mosquitoes, and has been proven highly effective in many endemic regions. *Vitamin A Deficiency* - **Vitamin A supplementation** through MDA is a highly effective, widely implemented strategy to combat **Vitamin A Deficiency (VAD)** in young children and pregnant women in areas where VAD is a public health problem. - It significantly reduces childhood morbidity and mortality from infectious diseases and prevents **xerophthalmia**. *Worm infestation* - **Deworming programs** using MDA, particularly for **soil-transmitted helminths (STH)**, are highly effective in controlling intestinal worm infestations in school-aged children and other high-risk groups. - Regular administration of **albendazole** or **mebendazole** drastically reduces worm burden, improving nutritional status and school performance.
Question 6: A 45 year old female presents with the complaint of pain in the metacarpophalangeal, proximal interphalangeal and metatarsophalangeal joints of both right and left hands. Serology showed positive anti-CCP antibodies. She was placed on infliximab for control. Which of the following need to tested before starting treatment?
- A. G6PD
- B. PPD skin test (Correct Answer)
- C. Uric acid
- D. Complete blood count
Explanation: ***PPD skin test*** - **Infliximab** is a **TNF-alpha inhibitor**, which can **reactivate latent tuberculosis** (TB) by suppressing the immune response critical for containing the infection. [1] - A **PPD skin test** (or interferon-gamma release assay like Quantiferon) is essential to screen for latent TB before initiating treatment with biologics like infliximab to prevent severe active infection. [1] *G6PD* - **Glucose-6-phosphate dehydrogenase (G6PD) deficiency** is primarily relevant when prescribing drugs that can cause **hemolysis**, such as certain antimalarials or sulfonamides. - It does not have a direct interaction or contraindication with infliximab, and screening is not standard practice before starting TNF-alpha inhibitors. *Uric acid* - **Uric acid levels** are primarily monitored in conditions like **gout** or when using medications that affect uric acid metabolism. - They are not a standard pre-treatment screening test for patients starting infliximab for rheumatoid arthritis. *Complete blood count* - A **complete blood count (CBC)** is generally part of routine workup for many conditions and can help assess baseline blood cell counts before starting any significant medication. [1] - While useful for monitoring during treatment, it is not the critical specific test required to prevent a severe infectious complication, like a PPD test, before starting infliximab. [1]
Question 7: A 45-year-old male having a long history of cigarette smoking presented with gangrene of the left foot, which was treated with an amputation. Representative sections from the specimen revealed the presence of arterial thrombus with neutrophilic infiltrate in the arterial wall, as well as inflammation extending into the adjacent veins and nerves. What is the most probable diagnosis?
- A. Takayasu arteritis
- B. Giant cell arteritis
- C. Hypersensitivity angiitis
- D. Thromboangiitis obliterans (Correct Answer)
Explanation: ***Thromboangiitis obliterans*** - This condition is strongly linked to **heavy smoking** and is characterized by segmental, thrombosing inflammation of medium-sized and small arteries, along with associated veins and nerves, leading to **gangrene** in the extremities [1]. - The presence of **arterial thrombus with neutrophilic infiltrate** in the arterial wall, and inflammation extending to adjacent **veins and nerves**, is a classic histopathological finding [1]. *Takayasu arteritis* - This is a **large-vessel vasculitis** primarily affecting the aorta and its main branches, leading to **absent pulses** ("pulseless disease") and claudication in the upper extremities [2]. - It typically does not involve the small and medium-sized arteries of the distal extremities or present with inflammation extending to adjacent veins and nerves as described. *Giant cell arteritis* - This is a **large-vessel vasculitis** predominantly affecting the temporal arteries and other arteries originating from the aorta in individuals over 50 years of age, presenting with **headache**, **jaw claudication**, and **visual disturbances** [2]. - Histopathology reveals **granulomatous inflammation** with giant cells, not the neutrophilic infiltrate and involvement of veins/nerves seen in this case [2]. *Hypersensitivity angiitis* - This refers to **leukocytoclastic vasculitis** affecting small vessels (arterioles, capillaries, venules) and is often associated with drug reactions or systemic diseases, typically presenting with **palpable purpura** [3]. - It primarily involves small vessels and lacks the characteristic segmental thrombosing inflammation of arteries, veins, and nerves seen in the given scenario, nor is it definitively linked to smoking leading to gangrene [3]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Cardiovascular Disease, pp. 280-281. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 516-517. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Cardiovascular Disease, pp. 279-280.
Question 8: What is the drug of choice for treating isosporiasis?
- A. Penicillin G
- B. Benzathine penicillin
- C. Co-trimoxazole (Correct Answer)
- D. Albendazole
Explanation: ***Co-trimoxazole*** - **Co-trimoxazole** (trimethoprim-sulfamethoxazole) is the **drug of choice** for treating **isosporiasis**, especially in immunocompromised individuals. - It works by inhibiting **folic acid synthesis**, which is essential for parasitic replication. *Penicillin G* - **Penicillin G** is a **beta-lactam antibiotic** primarily used for treating **bacterial infections**, particularly those caused by susceptible Gram-positive organisms. - It has **no activity** against **Isospora belli**, a parasitic protozoan. *Benzathine penicillin* - **Benzathine penicillin** is a **long-acting form of penicillin G** used for treating **syphilis** and preventing **rheumatic fever**. - It is **ineffective** against **parasitic infections** like isosporiasis. *Albendazole* - **Albendazole** is a broad-spectrum **anthelmintic drug** effective against various **intestinal worms** and some **tissue parasites**. - While it is an antiparasitic, it is **not effective** against **Isospora belli**; co-trimoxazole is the preferred treatment.
Question 9: 23 years old woman complains of recurrent acne over her face. History revealed that she had taken topical antibiotics for her acne without any significant improvement. Which one of the following tetracyclines is most preferred for her acne?
- A. Doxycycline (Correct Answer)
- B. Oxytetracycline
- C. Minocycline
- D. Demeclocycline
Explanation: ***Doxycycline*** - **Doxycycline** is a commonly preferred tetracycline for acne due to its **anti-inflammatory properties** and efficacy against *P. acnes* at sub-antimicrobial doses. - Its **longer half-life** allows for once-daily dosing, improving patient adherence compared to other tetracyclines. *Oxytetracycline* - While effective against *P. acnes*, **oxytetracycline** generally requires higher doses and more frequent administration, which can lead to poorer patient compliance. - It often causes **gastric irritation**, making it less favorable for long-term acne management. *Minocycline* - **Minocycline** is also effective for acne but is associated with a higher risk of **side effects** like dizziness, headache, and hyperpigmentation (e.g., skin, teeth). - Its potential for **drug-induced lupus-like syndrome** and **hepatotoxicity** makes it less preferred compared to doxycycline, especially for prolonged use. *Demeclocycline* - **Demeclocycline** is primarily used as an **ADH antagonist** for treating syndrome of inappropriate antidiuretic hormone (SIADH) and is not a first-line treatment for acne. - It has a higher incidence of **photosensitivity** and overall greater renal toxicity compared to other tetracyclines, making it unsuitable for acne.
Question 10: Most reliable indicator of some dehydration?
- A. Lethargy
- B. Delayed skin pinch
- C. Thirst (Correct Answer)
- D. Sunken eyes
Explanation: Thirst - **Thirst** is a physiological response to even mild dehydration and is often the **earliest and most reliable indicator** that the body needs fluids [1], [2]. - It reflects an increase in **plasma osmolality**, signaling the brain to initiate fluid-seeking behaviors [1], [2]. *Lethargy* - **Lethargy** indicates more severe dehydration or other underlying conditions, making it a less specific and sensitive early indicator. - It suggests significant neurological impairment due to fluid and electrolyte imbalances, rather than just some dehydration. *Delayed skin pinch* - A **delayed skin pinch** (decreased skin turgor) is a sign of *significant* dehydration, indicating a substantial loss of interstitial fluid. - This sign is often less reliable in infants and the elderly due to differences in skin elasticity. *Sunken eyes* - **Sunken eyes** are a sign of more **moderate to severe dehydration**, reflecting significant fluid volume depletion, especially in infants. - It is not an early or subtle indicator of "some dehydration" but rather a late manifestation [3].
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