Viral Skin Infections

Viral Skin Infections Indian Medical PG Question 1: Which of the following medications is not indicated for the treatment or prophylaxis of seasonal influenza?

• A. Amantadine
• B. Rimantadine
• C. Oseltamivir
• D. Acyclovir (Correct Answer)

Viral Skin Infections Explanation: ***Acyclovir*** - **Acyclovir** is an antiviral medication specifically used to treat infections caused by **herpes viruses** (e.g., HSV, VZV), not influenza viruses. - It works by inhibiting **viral DNA polymerase**, a mechanism distinct from how anti-influenza drugs act. - **This drug has never been indicated for influenza** - it is the correct answer to this "not indicated" question. *Amantadine* - **Amantadine** is an M2 ion channel inhibitor that **was indicated** for influenza A treatment and prophylaxis. - Although no longer recommended due to widespread **resistance** among circulating influenza strains, it remains a drug that was formally indicated for seasonal influenza. *Rimantadine* - **Rimantadine** is also an M2 ion channel inhibitor, structurally related to amantadine, with a similar mechanism of action. - Like amantadine, it **was indicated** for influenza treatment or prophylaxis but is no longer recommended due to high rates of **resistance** in circulating influenza A viruses. *Oseltamivir* - **Oseltamivir** is a **neuraminidase inhibitor** currently approved and recommended for the treatment and prophylaxis of both influenza A and B. - It reduces viral spread by preventing the release of new virions from infected cells and remains a first-line agent for seasonal influenza.

Viral Skin Infections Indian Medical PG Question 2: Which pox virus does Variola belong to?

• A. Parapoxvirus
• B. Orthopoxvirus (Correct Answer)
• C. Yatapox virus
• D. Molluscipox virus

Viral Skin Infections Explanation: ***Orthopoxvirus*** - **Variola virus**, the causative agent of **smallpox**, is a member of the **Orthopoxvirus genus**. - Other notable members of this genus include **vaccinia virus** (used in smallpox vaccine) and **monkeypox virus**. *Parapoxvirus* - This genus includes viruses such as **Orf virus**, which causes contagious pustular dermatitis in sheep and goats, occasionally transmitted to humans. - Parapoxviruses typically cause localized skin lesions and are not associated with **smallpox**. *Yatapox virus* - The **Yatapox virus genus** includes the **Tanapox virus** and **Yabapox virus**, which primarily affect monkeys but can cause mild, self-limiting skin lesions in humans. - They are distinct from the **Variola virus** and do not cause smallpox. *Molluscipox virus* - This genus contains **Molluscum contagiosum virus**, which causes **molluscum contagiosum**, a common skin infection characterized by small, flesh-colored, dome-shaped papules. - It is genetically and clinically distinct from **Variola virus**.

Viral Skin Infections Indian Medical PG Question 3: A patient presents with painful vesicles as shown in the image. What is the diagnosis?

• A. Chancroid
• B. Syphilis
• C. Herpes (Correct Answer)
• D. Candidiasis

Viral Skin Infections Explanation: ***Herpes*** - The image shows a cluster of **small, painful vesicles on an erythematous base**, which is highly characteristic of a herpes simplex virus (HSV) infection. - These lesions typically evolve into ulcers, crust over, and heal, and are often recurrent. *Chancroid* - Chancroid presents as **painful, soft chancres** (ulcers) with irregular, undermined borders and a gray or yellow base, often accompanied by **buboes** (enlarged, tender lymph nodes). - It does not typically manifest as clusters of small vesicles. *Syphilis* - Primary syphilis presents as a **painless chancre**—a single, firm, ulcerated lesion with a clean base and raised borders. - Secondary syphilis can cause a variety of skin manifestations, but not painful vesicles. *Candidiasis* - Cutaneous candidiasis usually appears as a **red, moist rash with satellite lesions** (smaller papules or pustules spreading from the main rash), often in skin folds. - While it can be inflammatory and itchy, it does not typically form discreet painful vesicles as seen in the image.

Viral Skin Infections Indian Medical PG Question 4: A 25-year-old male presents with a cluster of vesicles along the dermatome on his chest and back. He complains of burning pain in the same area. What is the most likely diagnosis?

• A. Herpes zoster (Correct Answer)
• B. Contact dermatitis
• C. Herpes simplex
• D. Impetigo

Viral Skin Infections Explanation: ***Herpes zoster*** - The classic presentation of **vesicular rash along a dermatome** with **burning pain** is highly characteristic of herpes zoster (shingles). - This condition is caused by the **reactivation of the varicella-zoster virus (VZV)**, which lies dormant in sensory ganglia. *Contact dermatitis* - This condition typically presents as an **itchy, erythematous rash** that appears after contact with an allergen or irritant. - While vesicles can be present, the rash is usually not strictly confined to a single dermatome and **burning pain is less common** than itching. *Herpes simplex* - Herpes simplex virus (HSV) typically causes **localized clusters of vesicles** on mucosal surfaces (e.g., oral, genital) or skin. - It does not usually present with a **dermatomal distribution** on the trunk as described in the vignette. *Impetigo* - Impetigo is a **bacterial skin infection** characterized by **honey-crusted lesions** or pustules. - While it can involve vesicles, it does not follow a **dermatomal pattern** and is caused by bacteria, not a viral reactivation.

Viral Skin Infections Indian Medical PG Question 5: A 23-year-old woman presents with recurrent genital herpes despite continuous suppressive therapy with valacyclovir 1g daily for 6 months. She reports adherence to medication. HIV test is negative. What is the most appropriate next step in management?

• A. Increase valacyclovir to 1g twice daily
• B. Perform viral culture with acyclovir sensitivity testing (Correct Answer)
• C. Add topical foscarnet to current regimen
• D. Switch to famciclovir suppressive therapy

Viral Skin Infections Explanation: ***Perform viral culture with acyclovir sensitivity testing*** - **Recurrent genial herpes** despite **continuous suppressive therapy** with 1g daily valacyclovir is suggestive of possible **antiviral resistance**. - A **viral culture with sensitivity testing** is crucial to confirm resistance and guide appropriate treatment [1]. *Increase valacyclovir to 1g twice daily* - While increasing the dose might be considered in some cases of treatment failure, it is not the most appropriate first step here given the **recurrent infections** despite an already high dose and excellent adherence. - Doing so without first checking for **resistance** might delay appropriate management. *Add topical foscarnet to current regimen* - Topical foscarnet is generally reserved for **acyclovir-resistant herpes simplex virus (HSV)** infections, especially in immunocompromised patients, and is typically used as monotherapy or an alternative systemic treatment. - It would be premature to add an alternative agent without confirming **resistance** and the HSV strain. *Switch to famciclovir suppressive therapy* - Famciclovir and valacyclovir have similar mechanisms of action and **cross-resistance** is common, particularly if the resistance is due to a **thymidine kinase (TK) mutation**. - Switching medications without determining the cause of **treatment failure** is unlikely to be effective [1].

Viral Skin Infections Indian Medical PG Question 6: An 18-year-old man has facial and upper back lesions that have waxed and waned for the past 6 years. On physical examination, there are 0.3- to 0.9-cm comedones, erythematous papules, nodules, and pustules most numerous on the lower face and posterior upper trunk. Other family members have been affected by this condition at a similar age. The lesions worsen during a 5-day cruise to the Adriatic. Which of the following organisms is most likely to play a key role in the pathogenesis of these lesions?

• A. Propionibacterium acnes (Correct Answer)
• B. Herpes simplex virus type 1
• C. Group A β-hemolytic streptococcus
• D. Mycobacterium leprae

Viral Skin Infections Explanation: ***Propionibacterium acnes*** (now *Cutibacterium acnes*) - The presence of **comedones, papules, nodules, and pustules** on the face and upper back in an 18-year-old is classic for **acne vulgaris**. - **_P. acnes_** is a commensal bacterium that proliferates in clogged hair follicles, contributing to inflammation and lesion formation in acne due to its lipolytic activity and immune-activating properties. *Herpes simplex virus type 1* - **HSV-1** typically causes **oral herpes (cold sores)** or **genital herpes**, characterized by painful vesicles and ulcers. - The described lesions (comedones, papules, nodules, pustules) are not characteristic of HSV-1 infection. *Group A β-hemolytic streptococcus* - **Group A Strep** causes infections like **pharyngitis (strep throat)**, **impetigo**, or **cellulitis**, which are typically acute and rapidly spreading. - Its presence is not associated with chronic, polymorphic lesions characteristic of acne. *Mycobacterium leprae* - **_M. leprae_** is the causative agent of **leprosy**, presenting with skin lesions, nerve damage, and other systemic effects. - The skin lesions of leprosy are typically macules, papules, or nodules with sensory loss, not the comedones and pustules seen in acne.

Viral Skin Infections Indian Medical PG Question 7: A child presents with grouped vesicles on an erythematous base on the buttocks. What is the most likely diagnosis?

• A. Bullous impetigo
• B. Dermatitis herpetiformis
• C. Pemphigus
• D. Herpes simplex (Correct Answer)

Viral Skin Infections Explanation: ***Herpes simplex*** - Herpes simplex virus (HSV) classically presents with **grouped vesicles on an erythematous base**, which perfectly matches this clinical presentation. - In **children**, HSV commonly affects the **buttocks** through autoinoculation or direct contact, especially in the diaper area. - The lesions are typically **painful and pruritic**, and may be preceded by tingling or burning sensation. - Diagnosis is confirmed by **Tzanck smear** (multinucleated giant cells), **PCR**, or **viral culture**. - Treatment includes **acyclovir** or other antivirals, especially for severe or recurrent cases. *Dermatitis herpetiformis* - While DH does present with intensely pruritic, grouped vesicles on an erythematous base, it is **extremely rare in children** and typically presents in **adults (3rd-4th decade)**. - Classic sites include **extensor surfaces** (elbows, knees), scalp, and buttocks, but the pediatric presentation makes this diagnosis unlikely. - It is strongly associated with **celiac disease** and responds to **gluten-free diet** and **dapsone**. *Bullous impetigo* - Bullous impetigo presents with **flaccid bullae** that rupture to form **honey-colored crusts**, not grouped vesicles. - It is a **bacterial infection** caused by *Staphylococcus aureus* producing exfoliative toxin. - Common in **young children**, particularly in warm, humid conditions. *Pemphigus* - Pemphigus is **extremely rare in children** and causes **fragile bullae** that easily rupture, leading to erosions. - Typically affects **mucous membranes first** (oral cavity), then skin. - It is an **autoimmune blistering disease** with antibodies against desmoglein, causing intraepidermal acantholysis.

Viral Skin Infections Indian Medical PG Question 8: Which of the following is the MOST characteristic feature of skin tags (acrochordons)?

• A. They commonly occur on the neck and axilla.
• B. They have malignant potential.
• C. They are associated with seborrhoeic keratosis.
• D. They are typically pedunculated. (Correct Answer)

Viral Skin Infections Explanation: ***They are typically pedunculated.*** - **Skin tags (acrochordons)** are benign soft tissue tumors characterized by their **pedunculated morphology** - they are attached to the skin by a narrow stalk or pedicle. - This **pedunculated appearance** is the **most characteristic** and **defining feature** that distinguishes them from other benign skin lesions. - They are typically **soft, flesh-colored or hyperpigmented**, and range from 1-5 mm in size. *They commonly occur on the neck and axilla.* - While **skin tags** frequently occur in areas of friction such as the neck, axilla, eyelids, groin, and inframammary folds, this **location is not specific**. - Many other skin conditions also favor these sites, so location alone is not a characteristic diagnostic feature. *They are associated with seborrhoeic keratosis.* - There is **no established clinical association** between skin tags and seborrheic keratoses. - Both are common **benign skin growths** in adults but represent different pathological entities with different clinical appearances. *They have malignant potential.* - This is **incorrect**. Skin tags are **benign fibrous polyps** with **no malignant potential**. - They do not require removal unless symptomatic or for cosmetic reasons.

Viral Skin Infections Indian Medical PG Question 9: The following findings on Tzanck smear can be seen in:

• A. Herpes simplex
• B. Herpes zoster
• C. Paraneoplastic pemphigus
• D. All of the above (Correct Answer)

Viral Skin Infections Explanation: ***All of the above*** - The image displays multiple **acantholytic cells** (keratinocytes that have lost intercellular connections) with prominent nuclei, which are characteristic findings in several dermatological conditions. - A **Tzanck smear** is a rapid cytological test performed by scraping the base of a fresh blister, staining with Giemsa or Wright stain, and examining under microscopy. **Why all three conditions show similar findings:** *Herpes simplex* - Tzanck smear shows **multinucleated giant cells** with molding of nuclei and **balloon degeneration** of keratinocytes - Acantholytic cells are present due to viral cytopathic effect causing cell separation - These findings are **identical** to those seen in Herpes zoster *Herpes zoster* - Cannot be distinguished from Herpes simplex on Tzanck smear morphology alone - Shows the same **multinucleated giant cells** and **acantholytic keratinocytes** - Viral culture, PCR, or direct fluorescent antibody (DFA) testing needed for definitive differentiation *Paraneoplastic pemphigus* - Shows **acantholytic cells** (rounded keratinocytes with hyperchromatic nuclei) due to autoantibody-mediated destruction of intercellular adhesion - Unlike herpes infections, typically shows acantholytic cells **without** multinucleated giant cells - Definitive diagnosis requires direct immunofluorescence (DIF) on skin biopsy showing intercellular and basement membrane zone IgG/C3 deposition **Note**: While Tzanck smear can show acantholytic cells in all three conditions, the **pattern differs** - herpes shows multinucleated giant cells prominently, while pemphigus shows isolated acantholytic cells. Clinical correlation and confirmatory tests are essential for accurate diagnosis.

Viral Skin Infections Indian Medical PG Question 10: In which of the following conditions is the Koebner phenomenon most commonly observed?

• A. Psoriasis (Correct Answer)
• B. Lichen planus
• C. All of the options
• D. Viral warts

Viral Skin Infections Explanation: ***Correct: Psoriasis*** - **Psoriasis** is the **most classic and commonly cited example** of the Koebner phenomenon (isomorphic response) - New psoriatic plaques characteristically develop at sites of cutaneous trauma, scratches, or surgical incisions in 25-50% of psoriasis patients - This is a **pathognomonic feature** frequently tested in competitive exams and considered the prototype condition for demonstrating this phenomenon - The mechanism involves inflammatory cascades triggered by trauma in genetically predisposed skin *Incorrect: Lichen planus* - While lichen planus does exhibit the Koebner phenomenon with purplish polygonal papules appearing along scratch lines, it is **less commonly observed** compared to psoriasis - Seen in approximately 10-25% of lichen planus cases - Not considered the primary example when teaching about Koebner phenomenon *Incorrect: Viral warts* - Viral warts can demonstrate **pseudo-Koebner phenomenon** where new warts form along trauma lines due to viral inoculation - This is more accurately described as **autoinoculation** rather than true isomorphic response - Less commonly discussed in the context of classic Koebner phenomenon compared to psoriasis *Incorrect: All of the options* - While all three conditions can show Koebner-like responses, the question asks for "**most commonly observed**" - Psoriasis remains the **gold standard** and most frequently encountered example in clinical practice and medical literature

Viral Skin Infections Flashcard 1 of 8

Question: _____ is a painful hand vesicle that occurs when the skin comes in contact with HSV-1 or HSV-2 (common in dentists)

Answer: Herpetic whitlow

Viral Skin Infections Flashcard 2 of 8

Question: Recurrent target lesions on palms and sole is s/o _____ infection

Answer: HSV

Viral Skin Infections Flashcard 3 of 8

Question: What are two infectious causes of erythema multiforme?_____

Answer: HSV #1

Viral Skin Infections Flashcard 4 of 8

Question: _____ syndrome is a papular acrodermatitis seen as a reaction of skin to a viral infection, such as HBV or EBV

Answer: Gianotti Crosti

Viral Skin Infections Flashcard 5 of 8

Question: The _____ is a diagnostic test used to identify HSV or VZV through a smear of an opened skin vesicle.

Answer: Tzanck smear

Viral Skin Infections Flashcard 6 of 8

Question: Localized Kaposi varicelliform eruption may be self-resolving or may be treated with oral _____

Answer: acyclovir

Viral Skin Infections Flashcard 7 of 8

Question: Recurrent target lesions on palms and sole is s/o _____ infection

Answer: HSV

Viral Skin Infections Flashcard 8 of 8

Question: What are three causes of rash on the palms and soles?_____, Rickettsia rickettsii, Coxsackievirus A

Answer: 2 syphilis