Viral Skin Infections Practice Questions

Q: What is the most likely diagnosis?

Herpes zoster. ***Herpes zoster*** - Presents with characteristic **unilateral vesicles or ulcers** that follow a specific **dermatomal distribution**, commonly affecting the **trigeminal nerve** branches in oral cavity - The **painful, vesicular eruption** typically remains confined to one side and follows the anatomical nerve pathway, making it highly distinctive *Candidiasis* - Characterized by **white plaques** that can be wiped off, revealing an **erythematous base** underneath - Typically presents **bilaterally** and affects immunocompromised patients, diabetics, or those on antibiotics *Geographic tongue* - Features **map-like patches** with **red centers** and **white borders** on the **dorsal surface** of the tongue - This is a **benign condition** with migrating patterns that doesn't follow dermatomal distribution *Lichen planus* - Presents with **white reticular striae** (Wickham's striae) in a **lace-like pattern** on buccal mucosa - Typically affects **bilateral buccal mucosa** and doesn't follow unilateral dermatomal patterns

Q: Dew drops on rose petal appearance is seen in infection with which of the following?

Varicella zoster virus. **Explanation:** The classic clinical description **"dew drops on rose petal"** refers to the characteristic morphology of the primary rash in **Chickenpox**, caused by the **Varicella-Zoster Virus (VZV)**. 1. **Why Varicella-Zoster Virus is correct:** The rash typically begins as small, clear, thin-walled vesicles (the "dew drop") situated on an intensely erythematous, circular base (the "rose petal"). This appearance occurs because the virus causes intraepidermal acantholysis, leading to fluid accumulation. A hallmark of VZV is **pleomorphism**, where lesions at different stages of evolution (papules, vesicles, and crusts) are seen simultaneously in the same anatomical area. 2. **Why other options are incorrect:** * **Herpes genitalis (HSV-2):** While it also presents with vesicles on an erythematous base, these are typically **grouped (herpetiform)** and painful, rather than the scattered "dew drop" distribution seen in VZV. * **Candida:** Presents as bright red erythematous plaques with characteristic **satellite lesions** (pustules at the periphery), often in intertriginous areas. * **T. rubrum:** This is a dermatophyte causing Tinea corporis/cruris, characterized by **annular plaques** with central clearing and an active, scaly border. **High-Yield Clinical Pearls for NEET-PG:** * **Tzanck Smear:** Used for rapid diagnosis of VZV and HSV; look for **Multinucleated Giant Cells** and Cowdry Type A inclusion bodies. * **Centripetal Distribution:** VZV rash starts on the trunk and spreads to the face and extremities (opposite of Smallpox). * **Ramsay Hunt Syndrome:** Reactivation of VZV in the geniculate ganglion, leading to facial palsy and vesicles in the external auditory canal.

Q: The pseudo-isomorphic phenomenon is seen in which of the following dermatological conditions?

Molluscum contagiosum. **Explanation:** The **pseudo-isomorphic phenomenon** (also known as the pseudo-Koebner phenomenon) refers to the spread of infectious lesions along a line of trauma, such as scratching or shaving. Unlike the true Koebner phenomenon, which involves an inflammatory response, this occurs due to **autoinoculation** of an infectious agent into the skin. **1. Why Molluscum Contagiosum is correct:** Molluscum contagiosum is caused by a **Poxvirus**. The virus replicates within the epidermis, and when a lesion is traumatized, the infectious viral particles are mechanically spread along the scratch mark, leading to a linear distribution of new umbilicated papules. This is a classic example of autoinoculation. **2. Why the other options are incorrect:** * **A, B, and C (Psoriasis, Lichen Planus, Vitiligo):** These conditions exhibit the **True Koebner Phenomenon (Isomorphic Phenomenon)**. In these cases, non-specific trauma (like a scratch) triggers the development of new lesions of a pre-existing non-infectious skin disease in previously healthy skin. They are mediated by inflammatory and immunological pathways rather than infection. **High-Yield Clinical Pearls for NEET-PG:** * **True Koebner Phenomenon:** Seen in Psoriasis (most common), Lichen Planus, and Vitiligo. * **Pseudo-Koebner Phenomenon:** Seen in Molluscum contagiosum, Verruca (Warts), and Impetigo. * **Reverse Koebner:** Disappearance of a lesion following trauma (e.g., Psoriasis). * **Wolf’s Isotopic Response:** Occurrence of a new skin disease at the exact site of a previously healed, unrelated skin disease (most commonly seen after Herpes Zoster). * **Molluscum Contagiosum Key Feature:** Presence of **Henderson-Paterson bodies** (intracytoplasmic inclusion bodies) on histopathology.

Q: Which of the following is NOT a stage of herpetic lesions?

Chancre. The correct answer is **C. Chancre**. ### **Explanation** Herpetic lesions, caused by the **Herpes Simplex Virus (HSV-1 or HSV-2)**, follow a classic evolutionary sequence of stages. A **Chancre**, however, is the hallmark of **Primary Syphilis** (caused by *Treponema pallidum*). It is characterized as a painless, indurated, clean-based ulcer, which is etiologically and clinically distinct from the painful, grouped vesicles of herpes. **Evolution of Herpetic Lesions:** 1. **Prodrome:** Tingling, itching, or burning sensation. 2. **Vesicle (Option A):** Small, "dew-drop on a rose petal" grouped vesicles on an erythematous base. 3. **Pustulation/Ulceration (Option D):** Vesicles rupture to form shallow, painful, punched-out erosions or ulcers. 4. **Crusting (Option B):** The lesions dry up, forming crusts (scabs) before healing without scarring (unless secondary infection occurs). ### **NEET-PG High-Yield Pearls** * **Tzanck Smear:** The gold standard bedside test for Herpes. Look for **Multinucleated Giant Cells** and **Acantholytic cells**. * **Inclusion Bodies:** HSV shows **Cowdry Type A** intranuclear inclusion bodies (Lipschütz bodies). * **Differentiating Genital Ulcers:** * **Herpes:** Painful, multiple, superficial vesicles/ulcers. * **Chancre (Syphilis):** Painless, single, indurated ulcer. * **Chancroid (*H. ducreyi*):** Painful, soft, "ragged" ulcer with inguinal lymphadenopathy (Bubo). * **Drug of Choice:** Oral Acyclovir (inhibits DNA polymerase).

Q: A middle-aged male presents with multiple painful blisters on an erythematous base along the T3 dermatome on the trunk. Which of the following etiological agents is most likely to be implicated?

Varicella zoster virus. ### Explanation **Correct Answer: A. Varicella zoster virus** The clinical presentation of **painful blisters on an erythematous base** distributed along a **single dermatome** (T3) is the classic hallmark of **Herpes Zoster** (Shingles). This condition is caused by the reactivation of the **Varicella Zoster Virus (VZV)**, which remains latent in the sensory dorsal root ganglia after a primary infection (Chickenpox). The virus travels down the sensory nerve to the skin, resulting in a unilateral, dermatomal eruption that does not cross the midline. **Analysis of Incorrect Options:** * **B. Herpes simplex virus (HSV):** While HSV causes grouped vesicles on an erythematous base, it typically presents as recurrent lesions on the lips (HSV-1) or genitalia (HSV-2). It is generally not dermatomal in distribution. * **C. Human papilloma virus (HPV):** HPV causes various types of warts (Verruca). These are characterized by hyperkeratotic, flesh-colored papules, not painful vesicles or blisters. * **D. Pox virus:** The most common dermatological manifestation is **Molluscum Contagiosum**, which presents as firm, pearly, umbilicated papules, typically painless and non-vesicular. **High-Yield Clinical Pearls for NEET-PG:** * **Tzanck Smear:** A rapid bedside test for VZV and HSV. Look for **Multinucleated Giant Cells** and **Acantholytic cells**. * **Hutchinson’s Sign:** Vesicles on the tip of the nose indicating involvement of the nasociliary branch of the ophthalmic nerve; it predicts ocular involvement in Zoster Ophthalmicus. * **Post-Herpetic Neuralgia (PHN):** The most common complication, defined as pain persisting >90 days after the rash heals. * **Ramsay Hunt Syndrome:** VZV reactivation in the geniculate ganglion involving CN VII and VIII (triad of facial palsy, ear pain, and vesicles in the external auditory canal).

Q: Systemic acyclovir in herpes zoster is useful:

When started immediately after the onset of rash. **Explanation:** The primary goal of systemic acyclovir in Herpes Zoster (Shingles) is to inhibit viral replication. The drug acts as a nucleoside analogue that inhibits viral DNA polymerase. **Why Option A is correct:** Acyclovir is most effective when initiated within the **"Golden Window" of 48 to 72 hours** after the onset of the rash. During this early phase, viral replication is at its peak. Early administration significantly reduces the duration of viral shedding, accelerates the healing of crusts, and limits the severity of acute pain. Once the lesions have crusted over, viral replication has largely ceased, rendering the antiviral therapy ineffective. **Why other options are incorrect:** * **Option B:** While early treatment of Zoster may slightly reduce the incidence of **Post-Herpetic Neuralgia (PHN)**, acyclovir is not a treatment for established PHN. PHN is a neuropathic pain condition managed with gabapentinoids (Pregabalin/Gabapentin) or tricyclic antidepressants (Amitriptyline). * **Option C:** Systemic therapy is indicated for ocular involvement (Herpes Zoster Ophthalmicus), but it is certainly not limited to it. It is also indicated for elderly patients (>50 years), immunocompromised individuals, and those with severe truncal or limb involvement. **High-Yield Clinical Pearls for NEET-PG:** * **Dosage:** The dose for Herpes Zoster is **800 mg five times a day for 7 days** (much higher than the 200 mg dose used for Herpes Simplex). * **Valacyclovir/Famciclovir:** These are now preferred over acyclovir due to better bioavailability and less frequent dosing (TID). * **Hutchinson’s Sign:** Vesicles on the tip of the nose indicate involvement of the nasociliary nerve, predicting a high risk of ocular complications. * **Tzanck Smear:** Shows **Multinucleated Giant Cells** (common to both HSV and VZV).

Q: Multinucleate giant cells are seen in Tzank smear in which of the following conditions?

Varicella-zoster virus (VZV) infection. **Explanation:** The **Tzanck smear** is a rapid bedside diagnostic test used in dermatology to examine cells from the base of a vesicle. The presence of **multinucleate giant cells** (formed by the fusion of infected keratinocytes) is the hallmark cytological finding for infections caused by the **Herpesviridae** family. **1. Why Option A is Correct:** In **Varicella-zoster virus (VZV)** and **Herpes Simplex Virus (HSV)** infections, the virus causes characteristic cytopathic effects: acantholysis (loss of intercellular connections), ballooning degeneration, and the formation of multinucleated giant cells with "molding" of nuclei. **2. Why Other Options are Incorrect:** * **B. Bullous Pemphigoid:** A Tzanck smear typically shows numerous **eosinophils** and a lack of acantholytic cells, as the split is subepidermal. * **C. Toxic Epidermal Necrolysis (TEN):** The smear shows **necrotic keratinocytes** and inflammatory cells, but not multinucleate giant cells. * **D. Pemphigus:** While Tzanck smear is used here, it reveals **Acantholytic cells (Tzanck cells)**—which are rounded, large, intensely staining keratinocytes with a perinuclear halo—but these are typically **mononucleated**, not multinucleated. **Clinical Pearls for NEET-PG:** * **Mnemonic for Tzanck Smear:** "Tzanck Heavily" – **H**erpes simplex, **H**erpes zoster, **H**ailey-Hailey disease, and **P**emphigus vulgaris. * **Key Distinction:** Multinucleate giant cells = Viral (HSV/VZV); Mononucleate acantholytic cells = Pemphigus. * **Stains used:** Giemsa, Wright’s, or Leishman stain. * **Inclusion bodies:** Look for **Lipschütz bodies** (eosinophilic intranuclear inclusions) in HSV/VZV.

Q: What is the drug of choice for Herpes zoster?

Erythema multiforme. **Explanation:** The question asks for a condition associated with Herpes infections, specifically identifying **Erythema Multiforme (EM)** as the correct association. **Why Erythema Multiforme is correct:** Erythema Multiforme is a hypersensitivity reaction most commonly triggered by infections. **Herpes Simplex Virus (HSV)** is the most frequent precipitant (up to 90% of cases). While the question mentions Herpes Zoster, in clinical dermatology, the "Herpes group" of viruses is the classic trigger for EM. It presents with characteristic **"target" or "iris" lesions** (three concentric zones: a central dusky disk, a pale edematous ring, and an erythematous halo) typically on the palms, soles, and extensor surfaces. **Why other options are incorrect:** * **Urticaria:** This is a Type I hypersensitivity reaction (wheals) usually triggered by allergens, drugs, or physical factors, not specifically linked as a primary sequela of Herpes. * **Scabies:** This is a parasitic infestation caused by the mite *Sarcoptes scabiei*. It is unrelated to viral triggers. * **Lichen Planus:** This is an idiopathic inflammatory condition (6 P's: Planar, Purple, Polygonal, Pruritic, Papules, Plaques). While associated with Hepatitis C, it is not a classic reaction to Herpes. **NEET-PG High-Yield Pearls:** * **Drug of Choice for Herpes Zoster:** Oral **Acyclovir** (800 mg 5x/day for 7 days). Valacyclovir and Famciclovir are preferred for better bioavailability. * **Hutchinson’s Sign:** Vesicles on the tip of the nose indicating ophthalmic involvement in Zoster. * **Ramsay Hunt Syndrome:** Zoster involving the geniculate ganglion (triad: facial palsy, ear pain, and vesicles in the external auditory canal). * **Tzanck Smear:** Shows **Multinucleated Giant Cells** and Cowdry Type A inclusion bodies in Herpes infections.

Q: A 10-year-old boy develops an itchy, vesicular rash that is maximal on his face and trunk. Physical examination demonstrates a mixture of lesions, including macules, papules, vesicles, and crusted lesions. The mother reports that the lesions seem to be occurring in crops. Which of the following is the most likely diagnosis?

Varicella. ### Explanation **Correct Option: D (Varicella)** The clinical presentation is classic for **Chickenpox (Varicella)**, caused by the Varicella-Zoster Virus (VZV). The hallmark of Varicella is **pleomorphism**, where lesions at different stages of development (macules, papules, vesicles, and crusts) coexist simultaneously. This occurs because the rash appears in successive **"crops"** over 3–5 days. The distribution is typically **centripetal**, meaning it is maximal on the trunk and face, sparing the distal extremities. The characteristic vesicle is often described as a **"dewdrop on a rose petal."** **Why other options are incorrect:** * **A & B (Herpes Simplex I & II):** These typically present as localized, grouped (herpetiform) vesicles on an erythematous base, usually involving the orolabial or genital regions. They do not present with a generalized, pleomorphic rash in crops. * **C (Measles):** This is characterized by a prodrome of the "3 Cs" (Cough, Coryza, Conjunctivitis) and **Koplik spots**. The rash is maculopapular and starts behind the ears, spreading cranio-caudally. It is not vesicular and does not appear in crops. **High-Yield NEET-PG Pearls:** * **Tzanck Smear:** Shows **Multinucleated Giant Cells** (common to VZV and HSV). * **Infectivity:** Patients are infectious from 48 hours before the rash appears until all lesions have crusted over. * **Complications:** Secondary bacterial infection (most common) and cerebellar ataxia (specific to children). * **Congenital Varicella Syndrome:** Characterized by cicatricial skin scarring, limb hypoplasia, and ocular defects if the mother is infected in the first 20 weeks of pregnancy.

Q: What is true about the rash of chickenpox?

Centripetal. **Explanation:** Chickenpox (Varicella) is caused by the **Varicella-Zoster Virus (VZV)**. The distribution of its rash is a classic high-yield topic for NEET-PG. **Why Centripetal is Correct:** The rash of chickenpox follows a **centripetal distribution**, meaning it is most dense on the trunk (center) and less dense on the extremities (periphery). This is the opposite of Smallpox, which is centrifugal. The lesions typically appear first on the trunk and then spread to the face and limbs. **Analysis of Incorrect Options:** * **A. Deep seated:** Chickenpox vesicles are **superficial** and thin-walled, often described as **"dewdrops on a rose petal."** In contrast, Smallpox lesions are deep-seated and firm. * **C. Affects palms and soles:** Chickenpox characteristically **spares the palms and soles**. If a vesicular rash involves the palms and soles, clinicians should consider Hand-Foot-Mouth Disease (Coxsackievirus) or Secondary Syphilis. * **D. Slow evolution:** Chickenpox is known for **rapid evolution**. Lesions progress from macules to papules, vesicles, and crusts within hours. This leads to **pleomorphism** (different stages of the rash present simultaneously in the same area). **High-Yield Clinical Pearls for NEET-PG:** * **Pleomorphism:** This is the hallmark of chickenpox (all stages of rash seen at once). * **Tzanck Smear:** Shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies. * **Incubation Period:** 10–21 days. * **Infectivity:** From 1–2 days before the rash appears until all lesions have crusted over. * **Starry Sky Appearance:** A descriptive term for the pleomorphic rash distributed over the body.

Question 1

What is the most likely diagnosis?

Accepted Answer

Herpes zoster

Answer

Candidiasis

Answer

Geographic tongue

Answer

Lichen planus

Question 2

Dew drops on rose petal appearance is seen in infection with which of the following?

Accepted Answer

Varicella zoster virus

Answer

Herpes genitalis

Answer

Candida

Answer

T. rubrum

Question 3

The pseudo-isomorphic phenomenon is seen in which of the following dermatological conditions?

Accepted Answer

Molluscum contagiosum

Answer

Psoriasis

Answer

Lichen planus

Answer

Vitiligo

Question 4

Which of the following is NOT a stage of herpetic lesions?

Accepted Answer

Chancre

Answer

Vesicle

Answer

Crusting

Answer

Ulceration

Question 5

A middle-aged male presents with multiple painful blisters on an erythematous base along the T3 dermatome on the trunk. Which of the following etiological agents is most likely to be implicated?

Accepted Answer

Varicella zoster virus

Answer

Herpes simplex virus

Answer

Human papilloma virus

Answer

Pox virus

Question 6

Systemic acyclovir in herpes zoster is useful:

Accepted Answer

When started immediately after the onset of rash

Answer

For post-herpetic neuralgia

Answer

For ocular lesions only

Answer

All of the above

Question 7

Multinucleate giant cells are seen in Tzank smear in which of the following conditions?

Accepted Answer

Varicella-zoster virus (VZV) infection

Answer

Bullous pemphigoid

Answer

Toxic epidermal necrolysis

Answer

Pemphigus

Question 8

What is the drug of choice for Herpes zoster?

Accepted Answer

Erythema multiforme

Answer

Urticaria

Answer

Scabies

Answer

Lichen planus

Question 9

A 10-year-old boy develops an itchy, vesicular rash that is maximal on his face and trunk. Physical examination demonstrates a mixture of lesions, including macules, papules, vesicles, and crusted lesions. The mother reports that the lesions seem to be occurring in crops. Which of the following is the most likely diagnosis?

Accepted Answer

Varicella

Answer

Herpes simplex I

Answer

Herpes simplex II

Answer

Measles

Question 10

What is true about the rash of chickenpox?

Accepted Answer

Centripetal

Answer

Deep seated

Answer

Affects palms and soles

Answer

Slow evolution

Viral Skin Infections — MCQs

Viral Skin Infections — MCQs

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