Parasitic Skin Infections Practice Questions

Q: Treatment of choice for scabies in an infant < 6 months is?

Permethrin. ***Permethrin*** - **Permethrin 5% cream** is the **first-line treatment** for scabies in infants and children, including those **aged 2 months and older**. - It is highly effective (95-97% cure rate), safe, and well-tolerated with minimal systemic absorption. - For infants **< 2 months**, permethrin can be used off-label with caution, though some guidelines prefer sulfur ointment in this very young age group. - Applied from neck down (including scalp in infants), left for 8-14 hours, then washed off; single application is usually sufficient. - **Recommended by CDC, AAP, and IAP** as the preferred scabicide for infants and children. *Sulfur ointment* - **5-10% sulfur ointment** is a safe and effective alternative, especially for infants **< 2 months** where permethrin data is limited. - It is the oldest scabicide with an excellent safety profile and no systemic toxicity. - Disadvantages include unpleasant odor, skin irritation, staining of clothes, and need for application on 3 consecutive nights. - Often considered when permethrin is unavailable or contraindicated. *Crotamiton* - **Crotamiton 10% cream/lotion** has limited efficacy (50-70% cure rate) compared to permethrin. - It is considered a **second or third-line agent** due to variable effectiveness. - Requires application for 2-5 consecutive days, which affects compliance. - Not recommended as first-line treatment in current guidelines. *Ivermectin* - **Oral ivermectin** is contraindicated in infants < 15 kg or < 5 years of age due to lack of safety data. - It does not cross the blood-brain barrier well in very young children, raising theoretical safety concerns. - Reserved for crusted scabies or treatment failures in older children and adults.

Q: In scabies which skin layer is affected?

Stratum corneum. ***Stratum corneum*** - The **Sarcoptes scabiei** mite burrows into the **stratum corneum**, the outermost layer of the epidermis, to lay its eggs. - This superficial burrowing nature explains the characteristic **linear lesions** and intense **pruritus** seen in scabies. *Stratum basale* - The **stratum basale** is the deepest layer of the epidermis, responsible for **cell proliferation** and skin renewal. - Scabies mites do not typically burrow this deep; their activity is confined to more superficial layers. *Stratum lucidum* - The **stratum lucidum** is a thin, clear layer found only in **thick skin**, such as the palms and soles. - While scabies can affect these areas, the mites do not specifically target or reside in this particular layer. *Stratum germinativum* - The **stratum germinativum** is an older term that refers collectively to the **stratum basale** and sometimes the **stratum spinosum**, where active cell division occurs. - Scabies mites burrow superficially and do not primarily affect these layers.

Q: Which of the following is not a feature of scabies?

Genitalia are not affected. ***Genitalia are not affected*** - Scabies can affect almost any part of the body, including the **genitalia**, characterized by the presence of **scrotal nodules** in men. - The mite *Sarcoptes scabiei* commonly infests warm, moist areas and skin folds, making the genitalia a frequent site of involvement. *Serpentine burrow* - **Burrows** are a classic diagnostic sign of scabies caused by the female mite tunneling under the skin to lay eggs. - These burrows often appear as fine, wavy, **serpiginous lines**, typically a few millimeters to a centimeter long. *Severe itching* - **Intense pruritus**, especially **worse at night**, is the most common and distressing symptom of scabies. - This itching is an allergic reaction to the mites, their eggs, and their feces. *Web space affection* - The **finger and toe web spaces** are among the most common sites for scabies infestation. - These areas provide a warm, moist, and protected environment ideal for mite activity and burrow formation.

Q: A pregnant lady presents with itchy hand lesions, and her husband also develops similar symptoms. What is the most appropriate treatment for this condition?

Permethrin. ***Permethrin*** - **Permethrin** cream (5%) is the first-line treatment for **scabies** in pregnant and lactating women due to its safety profile and effectiveness. - It works by paralyzing and killing the scabies mites and their eggs, and should be applied to the entire body from the neck down, washed off after 8-14 hours, and repeated in 7 days. *Topical corticosteroids* - While beneficial for reducing **inflammation and itching**, topical corticosteroids do not eliminate the **scabies mites** responsible for the infection. - They may provide symptomatic relief but cannot cure the underlying parasitic infestation. *Benzyl benzoate* - **Benzyl benzoate** is an effective **scabicide** but is generally considered a second-line option, especially in pregnancy, due to potential for **skin irritation** and limited safety data compared to permethrin. - It is not recommended as a first-line treatment in pregnant women due to concerns about systemic absorption and potential effects on the fetus. *Ivermectin* - Oral **ivermectin** is effective for scabies treatment, especially in crusted scabies or when topical treatments fail, but its use in **pregnancy** is typically avoided due to insufficient safety data regarding fetal effects. - While considered effective by some, the lack of robust safety data for pregnant women makes it a less preferred option than permethrin.

Q: Maculae cerulea is seen in which of the following conditions?

Pediculosis pubis. ***Pediculosis pubis*** - **Maculae ceruleae** are characteristic **blue-gray macules** (also known as blue spots) pathognomonic of infestation with **Pthirus pubis** (pubic lice or crab lice). - These spots are caused by the **louse's saliva** which contains anticoagulants that lead to small hemorrhages and subsequent breakdown of hemoglobin, producing the distinctive blue-gray discoloration. - The lesions are typically found on the **trunk, thighs, and axillae** where the lice feed. *Erythema multiforme* - This condition presents with diverse lesions, most notably the **target lesion**, which is not a blue-gray macule. - It is an acute, self-limited, and sometimes recurrent inflammatory disorder of the skin and mucous membranes, often triggered by infections (e.g., HSV) or medications. *Toxic epidermal necrolysis* - This is a severe, life-threatening skin condition characterized by widespread **epidermal detachment and blistering**, resembling a severe burn. - It does not present with discrete blue macules but rather with extensive skin sloughing. *Lichen planus* - Lichen planus typically presents with **pruritic, polygonal, planar, purple papules and plaques** (the 4 Ps). - It is an inflammatory condition affecting the skin, hair, nails, and mucous membranes, and it does not feature blue-gray maculae.

Q: All of the following are part of the treatment of scabies except?

Long term oral steroids. ***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.

Q: What is the treatment of choice for scabies in pregnancy?

Permethrin. ***Permethrin*** - **Permethrin** cream (5%) is the **treatment of choice** for scabies in pregnant women due to its **safety profile** and **efficacy**. - It works by **neurotoxicity** to the mite, causing paralysis and death, and has **minimal systemic absorption**, reducing risk to the fetus. *Gamma-benzene hexachloride* - This medication, also known as **lindane**, is generally **contraindicated in pregnancy** due to potential for **neurotoxicity** and transplacental absorption. - It can cause severe adverse effects such as **seizures** and aplastic anemia, making it unsafe for both mother and fetus. *No treatment necessary* - **Scabies is a parasitic infestation** that requires treatment to eradicate the mites and alleviate symptoms such as **intense itching** and skin lesions. - Untreated scabies can lead to **secondary bacterial infections** due to scratching, and the condition will not resolve on its own. *Ivermectin* - While effective for scabies, **oral ivermectin is generally not recommended** for use in pregnancy due to limited safety data and potential for **embryotoxicity** in animal studies. - It is typically reserved for cases of **crusted scabies** or when topical treatments have failed and the benefits outweigh the risks.

Q: 26-year-old man from Bihar presents with erythematous papules on the face and back of the neck, which are hypopigmented and normoaesthetic, with no nerve thickening. A history of prolonged fever in childhood is present. What is the diagnosis?

Dermal leishmaniasis (PKDL). ***Dermal leishmaniasis (PKDL)*** - PKDL presents with **erythematous papules** on the face and neck, which are **hypopigmented and normoaesthetic** (intact sensation), fitting the patient's description perfectly. - A history of **prolonged fever in childhood** in Bihar is highly suggestive of prior **visceral leishmaniasis (kala-azar)**, after which PKDL typically develops (months to years post-treatment). - The **absence of nerve thickening** and **normal sensation** are key features distinguishing PKDL from leprosy. - Bihar is an **endemic area** for visceral leishmaniasis in India. *Tuberculoid leprosy* - Characterized by **hypopigmented, anaesthetic patches** with **thickened nerves** - both features are absent in this case. - The **normoaesthetic** nature of lesions here rules out tuberculoid leprosy. - Lesions are typically **well-demarcated** and few in number. *Lepromatous leprosy* - Involves widespread, symmetrical lesions that are often **erythematous nodules** or **diffuse infiltrations**, with multiple nerve involvements. - Would show **nerve thickening** and eventual sensory loss, which are not present here. - The clinical picture does not match lepromatous leprosy. *Lupus vulgaris* - A form of **cutaneous tuberculosis** presenting as red-brown plaques with an **"apple-jelly" appearance** on diascopy. - While it can occur on the face, there is no history of fever or connection to visceral leishmaniasis. - The morphology (papules vs plaques) and epidemiological context favor PKDL.

Q: Which of the following statements about scabies is false?

Pruritus is predominantly absent.. ***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.

Q: A child has multiple itchy papular lesions on the genitalia and fingers, and similar lesions are also seen in the younger brother. Which of the following is the most possible diagnosis?

Scabies. ***Scabies*** - The presentation of **itchy papular lesions** (especially on the **genitalia and fingers**) in a child, along with similar lesions in a younger sibling, is highly suggestive of **scabies**. This pattern indicates an infectious, transmissible skin condition. - **Scabies** is caused by the *Sarcoptes scabiei* mite, which burrows into the skin, leading to intense itching, particularly at night, and characteristic lesions often found in interdigital spaces, wrists, elbows, axillae, umbilicus, belt line, buttocks, and genitalia. *Localized papular urticaria* - While characterized by **itchy papules**, **papular urticaria** usually represents an allergic reaction to insect bites and is typically localized and does not spread directly to other family members in the same manner as an infestation. - The **transmissible nature** and typical distribution (genitalia, fingers) described in the question are not characteristic of simple papular urticaria. *Chronic atopic dermatitis* - **Atopic dermatitis** is a chronic inflammatory skin condition characterized by **eczematous lesions**, severe itching, and dry skin, often with a history of allergies or asthma. - While it can cause itchy lesions, it typically presents with distinct **eczematous patches** or plaques, often in flexural areas, and is not directly transmissible between siblings in the way suggested by the scenario. *Irritant contact dermatitis* - **Irritant contact dermatitis** is caused by direct skin irritation from contact with a substance, leading to red, itchy, or burning rash, often with vesicles or blisters. - It is unlikely to cause a widespread rash involving specific areas like the genitals and fingers in two siblings simultaneously unless both were exposed to the same irritant, which is less likely than a transmissible infestation given the description.

Question 1

Treatment of choice for scabies in an infant < 6 months is?

Accepted Answer

Permethrin

Answer

Crotamiton

Answer

Sulfur ointment

Answer

Ivermectin

Question 2

In scabies which skin layer is affected?

Accepted Answer

Stratum corneum

Answer

Stratum basale

Answer

Stratum lucidum

Answer

Stratum germinativum

Question 3

Which of the following is not a feature of scabies?

Accepted Answer

Genitalia are not affected

Answer

Serpentine burrow

Answer

Severe itching

Answer

Web space affection

Question 4

A pregnant lady presents with itchy hand lesions, and her husband also develops similar symptoms. What is the most appropriate treatment for this condition?

Accepted Answer

Permethrin

Answer

Benzyl benzoate

Answer

Topical corticosteroids

Answer

Ivermectin

Question 5

Maculae cerulea is seen in which of the following conditions?

Accepted Answer

Pediculosis pubis

Answer

Erythema multiforme

Answer

Toxic epidermal necrolysis

Answer

Lichen planus

Question 6

All of the following are part of the treatment of scabies except?

Accepted Answer

Long term oral steroids

Answer

Topical Permethrin

Answer

Oral antihistamines

Answer

Oral ivermectin

Question 7

What is the treatment of choice for scabies in pregnancy?

Accepted Answer

Permethrin

Answer

Gamma-benzene hexachloride

Answer

No treatment necessary

Answer

Ivermectin

Question 8

26-year-old man from Bihar presents with erythematous papules on the face and back of the neck, which are hypopigmented and normoaesthetic, with no nerve thickening. A history of prolonged fever in childhood is present. What is the diagnosis?

Accepted Answer

Dermal leishmaniasis (PKDL)

Answer

Tuberculoid leprosy

Answer

Lepromatous leprosy

Answer

Lupus vulgaris

Question 9

Which of the following statements about scabies is false?

Accepted Answer

Pruritus is predominantly absent.

Answer

Scabies is caused by the mite Sarcoptes scabiei

Answer

Not exclusively transmitted sexually.

Answer

Erythematous papules develop due to delayed type 4 hypersensitivity.

Question 10

A child has multiple itchy papular lesions on the genitalia and fingers, and similar lesions are also seen in the younger brother. Which of the following is the most possible diagnosis?

Accepted Answer

Scabies

Answer

Localized papular urticaria

Answer

Chronic atopic dermatitis

Answer

Irritant contact dermatitis

Parasitic Skin Infections — MCQs

Parasitic Skin Infections — MCQs

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