Pediculosis — MCQs
A child comes with a circular 3cm x 3cm scaly patchy hair loss with itching in the lesions. The investigation of choice is
Wood's lamp is not used for diagnosing:
Which of the following diseases is not transmitted by lice?
Scabies oral treatment of choice:
Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
Which of the following statements about pediculosis pubis is MOST accurate?
What is the causative agent for the lesion on penis shown below?
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:
Pediculosis Indian Medical PG Practice Questions and MCQs
Question 1: A child comes with a circular 3cm x 3cm scaly patchy hair loss with itching in the lesions. The investigation of choice is
- A. Tzanck smear
- B. Gram stain
- C. KOH mount (Correct Answer)
- D. Split skin smear
Explanation: ***Correct: KOH mount (Potassium Hydroxide mount)*** - A **KOH mount** is the investigation of choice for suspected **dermatophyte infections** (tinea capitis), which commonly present as circular, scaly patches of hair loss with itching in children. - It involves dissolving keratinous material to visualize **fungal hyphae** and spores directly under a microscope. - This is a quick, cost-effective, and highly specific first-line diagnostic test. *Incorrect: Tzanck smear* - A **Tzanck smear** is primarily used to diagnose **viral infections** like herpes simplex or varicella-zoster by identifying multinucleated giant cells. - It is not effective for detecting fungal elements responsible for scaly hair loss. *Incorrect: Gram stain* - A **Gram stain** is a technique used to classify **bacteria** based on their cell wall properties. - It would not reveal fungal hyphae or spores relevant to the described condition. *Incorrect: Split skin smear* - A **split skin smear** (or slit-skin smear) is typically used in the diagnosis of **leprosy** to identify acid-fast bacilli. - This technique involves scraping the dermis and is not suitable for diagnosing superficial fungal infections.
Question 2: Wood's lamp is not used for diagnosing:
- A. Lichen planus (Correct Answer)
- B. Pityriasis versicolor
- C. Porphyria
- D. Vitiligo
Explanation: ***Lichen planus*** - **Wood's lamp** is generally not used for diagnosing **lichen planus** as the lesions typically do not fluoresce. - Diagnosis of lichen planus relies on its characteristic **violaceous, polygonal, pruritic papules and plaques** and often confirmed by **biopsy**. *Pityriasis versicolor* - **Wood's lamp** is useful for **pityriasis versicolor**, causing it to fluoresce a **yellowish-green or coppery-orange** color due to metabolic byproducts of *Malassezia* fungi. - This characteristic fluorescence helps in differentiating lesions from other skin conditions and in identifying subclinical involvement. *Porphyria* - **Wood's lamp** can be used to detect **reddish-pink fluorescence of urine** or skin in patients with **porphyria cutanea tarda** due to the accumulation of porphyrins. - This fluorescence is a key diagnostic indicator in certain types of **porphyria**, particularly those affecting the skin. *Vitiligo* - **Wood's lamp** enhances the contrast between depigmented and normally pigmented skin, making **vitiligo** lesions appear **bright bluish-white** due to the absence of melanin. - It is particularly useful for detecting subtle or small lesions of **vitiligo**, especially in individuals with lighter skin tones.
Question 3: Which of the following diseases is not transmitted by lice?
- A. Relapsing fever
- B. Trench fever
- C. Q fever (Correct Answer)
- D. Epidemic typhus
Explanation: ***Correct: Q fever*** - **Q fever** is caused by *Coxiella burnetii* and is primarily transmitted by **inhalation of aerosols** from infected animal products or excretions, not by lice - Exposure to infected livestock (cattle, sheep, goats) or their birth products is the most common route of transmission - This is a zoonotic disease with no arthropod vector involvement *Incorrect: Relapsing fever* - Louse-borne relapsing fever is caused by *Borrelia recurrentis* and transmitted by the body louse (*Pediculus humanus corporis*) - Infection occurs when infected lice are crushed, releasing bacteria into breaks in the skin - Characterized by recurrent episodes of fever, prevalent in areas with poor hygiene and overcrowding *Incorrect: Trench fever* - Caused by *Bartonella quintana* and transmitted by the body louse (*Pediculus humanus corporis*) through its feces - Infection occurs when louse feces are scratched into the skin or mucous membranes, or when inhaled - Associated with homelessness, overcrowding, and poor hygiene *Incorrect: Epidemic typhus* - Caused by *Rickettsia prowazekii* and transmitted by the body louse when its feces containing bacteria are rubbed into abraded skin or mucous membranes - Associated with poor hygiene and crowded conditions, particularly during wars, disasters, or refugee situations - Can cause severe systemic illness with high fever and rash
Question 4: 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 5: Statement 1 - A 59-year-old patient presents with flaccid bullae. Histopathology shows a suprabasal acantholytic split. Statement 2 - The row of tombstones appearance is diagnostic of Pemphigus vulgaris.
- A. Statements 1 & 2 are correct, 2 is not explaining 1 (Correct Answer)
- B. Statements 1 and 2 are correct and 2 is the correct explanation for 1
- C. Statements 1 and 2 are incorrect
- D. Statement 1 is incorrect
Explanation: ***Correct: Statements 1 & 2 are correct, 2 is not explaining 1*** **Analysis of Statement 1:** - A 59-year-old patient with **flaccid bullae** and **suprabasal acantholytic split** on histopathology is the classic presentation of **Pemphigus vulgaris** - The flaccid (easily ruptured) nature of bullae distinguishes it from tense bullae seen in bullous pemphigoid - The suprabasal location of the split (just above the basal layer) with acantholysis (loss of cell-to-cell adhesion) is pathognomonic - **Statement 1 is CORRECT** ✓ **Analysis of Statement 2:** - The **"row of tombstones" or "tombstone appearance"** is indeed a diagnostic histopathological feature of Pemphigus vulgaris - This appearance results from basal keratinocytes remaining attached to the basement membrane while suprabasal cells separate due to acantholysis - The intact basal cells standing upright resemble a row of tombstones - **Statement 2 is CORRECT** ✓ **Does Statement 2 explain Statement 1?** - Statement 2 describes a **histopathological appearance** (tombstone pattern) that is a **consequence** of the suprabasal split - However, it does NOT explain the **underlying cause** of the flaccid bullae or the suprabasal split - The true explanation involves **IgG autoantibodies against desmoglein 3 (and desmoglein 1)**, which attack intercellular adhesion structures (desmosomes), causing **acantholysis** - Therefore, **Statement 2 does NOT explain Statement 1** ✗ *Incorrect: Statement 2 is the correct explanation for Statement 1* - While both statements describe features of Pemphigus vulgaris, the tombstone appearance is a descriptive finding, not an explanatory mechanism *Incorrect: Statements 1 and 2 are incorrect* - Both statements are medically accurate descriptions of Pemphigus vulgaris features *Incorrect: Statement 1 is incorrect* - Statement 1 correctly describes the cardinal clinical and histopathological features of Pemphigus vulgaris
Question 6: Which of the following statements about pediculosis pubis is MOST accurate?
- A. Eggs (nits) attached to hair shafts confirm diagnosis (Correct Answer)
- B. It commonly infests scalp hair
- C. It requires systemic antibiotic treatment
- D. It is more contagious than other types of lice
Explanation: ***Eggs (nits) attached to hair shafts confirm diagnosis*** - The presence of **nits (eggs)** firmly attached to the hair shafts, particularly in the pubic region, is a **definitive diagnostic criterion** for pediculosis pubis. - These nits are typically oval, white or grayish, and cannot be easily removed, distinguishing them from dandruff. *It commonly infests scalp hair* - **Pediculosis pubis**, caused by *Pthirus pubis* (pubic louse or crab louse), primarily infests **coarse body hair**, most commonly in the pubic area. - **Scalp hair** is typically infested by *Pediculus humanus capitis* (head louse), which is a different species. *It requires systemic antibiotic treatment* - Pediculosis pubis is caused by an **ectoparasite** (louse), not a bacterial infection, and therefore does not require **systemic antibiotic treatment**. - Treatment involves topical insecticides like permethrin or malathion, and physical removal of lice and nits. *It is more contagious than other types of lice* - All types of lice are **highly contagious**, but pediculosis pubis is primarily transmitted through **sexual contact** or close bodily contact, making it a sexually transmitted infection (STI). - While easily spread, there is no evidence to suggest it is inherently more contagious than head lice, which spread easily through casual contact, especially among children.
Question 7: What is the causative agent for the lesion on penis shown below?
- A. Treponema pallidum (Correct Answer)
- B. HPV
- C. EBV
- D. KSHV
Explanation: ***Treponema pallidum*** * The image displays **condylomata lata**, which are moist, flat-topped, wart-like lesions that occur in secondary syphilis. * These lesions are highly infectious and contain a high concentration of **_Treponema pallidum_**. * _HPV_ * **Human Papillomavirus** causes **condylomata acuminata** (genital warts), which are typically exophytic, raised, and cauliflower-like or filiform, not the flat, broad lesions seen in the image. * While some HPV types are oncogenic, the morphology presented is not characteristic of typical HPV-induced warts. * _EBV_ * **Epstein-Barr virus** is associated with infectious mononucleosis and certain malignancies like nasopharyngeal carcinoma and Burkitt lymphoma, but not with penile lesions of this nature. * There is no direct causal link between typical EBV infection and genital warts or similar proliferative lesions. * _KSHV_ * **Kaposi's Sarcoma-associated Herpesvirus** (KSHV), also known as Human Herpesvirus 8 (HHV-8), causes Kaposi's sarcoma, a vascular tumor. * Kaposi's sarcoma lesions typically appear as **purple, red, or brown macules, plaques, or nodules**, which are distinct from the white/grey, moist, flat lesions shown.
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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