Parasitic Skin Infections — MCQs

Parasitic Skin Infections Indian Medical PG Practice Questions and MCQs

Question 61: What is the cause of scabies?

A. Mite (Correct Answer)
B. Virus
C. Fungus
D. Bacteria

Explanation: ***Correct Answer: Mite*** - Scabies is caused by an infestation of the skin by the human itch mite, **Sarcoptes scabiei var. hominis**. - These **microscopic mites** burrow into the upper layer of the skin, where they live and lay their eggs, causing intense itching and a characteristic skin rash. - The mite is an **arachnid ectoparasite**, and the condition is transmitted through prolonged direct skin-to-skin contact. *Incorrect: Bacteria* - **Bacterial infections** are caused by microorganisms like *Staphylococcus aureus* or *Streptococcus pyogenes* and typically lead to conditions like impetigo, cellulitis, or abscesses. - While scratching scabies lesions can lead to **secondary bacterial infections**, bacteria are not the primary cause of scabies itself. *Incorrect: Virus* - **Viral infections** result from viruses and cause a range of diseases such as herpes simplex, warts, or chickenpox, often characterized by specific lesion types or systemic symptoms. - Scabies is not a viral disease; it is an **ectoparasitic infestation**. *Incorrect: Fungus* - **Fungal infections** (mycoses) are caused by fungi and include conditions like ringworm (*tinea corporis*), athlete's foot (*tinea pedis*), or candidiasis, often presenting with scaly, itchy rashes. - The organism responsible for scabies is an **arachnid**, not a fungus.

Question 62: Which of the following is not a feature of scabies?

A. Genitalia are not affected (Correct Answer)
B. Serpentine burrow
C. Severe itching
D. Web space affection

Explanation: ***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.

Question 63: In scabies which skin layer is affected?

A. Stratum corneum (Correct Answer)
B. Stratum basale
C. Stratum lucidum
D. Stratum germinativum

Explanation: ***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.

Question 64: Maculae cerulea is seen in which of the following conditions?

A. Erythema multiforme
B. Toxic epidermal necrolysis
C. Lichen planus
D. Pediculosis pubis (Correct Answer)

Explanation: ***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.

Question 65: A pregnant lady presents with itchy hand lesions, and her husband also develops similar symptoms. What is the most appropriate treatment for this condition?

A. Benzyl benzoate
B. Topical corticosteroids
C. Permethrin (Correct Answer)
D. Ivermectin

Explanation: ***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.

Question 66: 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 67: What is the treatment of choice for scabies in pregnancy?

A. Permethrin (Correct Answer)
B. Gamma-benzene hexachloride
C. No treatment necessary
D. Ivermectin

Explanation: ***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.

Question 68: 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 69: 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?

A. Scabies (Correct Answer)
B. Localized papular urticaria
C. Chronic atopic dermatitis
D. Irritant contact dermatitis

Explanation: ***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 70: Which of the following conditions is associated with pseudo-buboes?

A. LGV
B. Chancroid
C. Granuloma inguinale (Correct Answer)
D. All of the options

Explanation: **Granuloma inguinale** - **Pseudo-buboes** are characteristic of granuloma inguinale and are subcutaneous granulomas that mimic the appearance of true buboes. - They are typically formed by **granulomatous tissue** in the inguinal region, not by inflamed lymph nodes as seen in true buboes. *Chancroid* - Chancroid is associated with true **buboes**, which are enlarged, painful, and often suppurative inguinal lymph nodes. - These buboes result from localized **lymphadenitis** due to *Haemophilus ducreyi* infection. *LGV* - **Lymphogranuloma venereum (LGV)** is known for causing characteristic **groove sign**, which involves deep inguinal lymphadenopathy that can lead to coalesced, firm, and matted nodes (true buboes) that may suppurate. - The buboes in LGV are typically **unilateral** and painful, evolving from initial infection with *Chlamydia trachomatis* serovars L1, L2, or L3. *All of the options* - This option is incorrect because while chancroid and LGV cause true buboes, only **granuloma inguinale** causes pseudo-buboes. - The distinction lies in the **etiology**; pseudo-buboes are granulomas, whereas true buboes are inflamed or suppurative lymph nodes.

Practice by Chapter

Scabies

Practice Questions

Pediculosis

Practice Questions

Cutaneous Larva Migrans

Practice Questions

Leishmaniasis

Practice Questions

Onchocerciasis

Practice Questions

Myiasis

Practice Questions

Tungiasis

Practice Questions

Cutaneous Amebiasis

Practice Questions

Cutaneous Manifestations of Malaria

Practice Questions

Ectoparasitic Infestations

Practice Questions

Diagnosis of Parasitic Infestations

Practice Questions

Antiparasitic Therapy

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free