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 Flashcard 1 of 5

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 5

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

Answer: HSV

Viral Skin Infections Flashcard 3 of 5

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

Answer: HSV #1

Viral Skin Infections Flashcard 4 of 5

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 5

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

Answer: Tzanck smear