Viral Skin Infections Practice Questions

Q: In a case of recurrent genital herpes with >6 episodes per year, which prophylactic regimen is most appropriate?

Valacyclovir 500mg daily. ***Valacyclovir 500mg daily*** - **Valacyclovir 500mg once daily** is the most appropriate prophylactic regimen for frequent recurrent genital herpes (≥6 episodes/year) - **Once-daily dosing** significantly improves patient adherence compared to multiple daily doses, which is crucial for long-term suppressive therapy - **Higher bioavailability** than acyclovir (54% vs 15-20%), allowing for less frequent dosing - **CDC-recommended** suppressive therapy regimen with proven efficacy in reducing recurrence frequency by 70-80% - For patients with ≥10 episodes per year, the dose can be increased to **1g once daily** *Acyclovir 400mg BD* - This is a **valid alternative** CDC-recommended suppressive regimen - However, **twice-daily dosing** is less convenient for long-term prophylaxis compared to once-daily valacyclovir - **Lower bioavailability** requires more frequent dosing to maintain therapeutic levels - May be preferred in resource-limited settings due to lower cost *Famciclovir 250mg BD* - This is also a **valid CDC-recommended** suppressive therapy option - **Twice-daily dosing** reduces adherence compared to once-daily regimens - Generally considered a **second-line alternative** when acyclovir or valacyclovir are not tolerated - Effective but less commonly used as first-line suppressive therapy *Acyclovir 200mg 5 times daily* - This is an **acute episodic treatment** regimen for active outbreaks, not for suppressive prophylaxis - **Five times daily dosing** is impractical for long-term use and has poor adherence - Used for treating initial or recurrent episodes, typically for 5 days duration

Q: A patient with anogenital warts has not responded to conventional therapy after 3 months. Next best step is:

HIV testing. ### HIV testing - **Persistent, recalcitrant anogenital warts** that do not respond to conventional therapy after 3 months are a strong indicator of **immunocompromise** [1]. - **HIV infection** is a common cause of immunosuppression that can lead to treatment failure for anogenital warts [1]. *Switch to imiquimod* - While **imiquimod** is a topical treatment for anogenital warts, switching therapies without investigating the cause of treatment failure is not the initial best step. - The lack of response suggests an underlying issue rather than simply a need for a different treatment type. *Continue same treatment longer* - Continuing the same treatment when there has been **no response after 3 months** is unlikely to be effective and delays appropriate management. - This approach does not address the underlying reason for treatment failure. *Biopsy lesion* - While a **biopsy** can be important to confirm the diagnosis or rule out malignancy, it is typically considered after addressing potential underlying causes for treatment resistance, such as **immunocompromise**. - In this scenario, the primary concern is the lack of response to therapy, which points towards an immune system issue.

Q: The most effective treatment for extensive molluscum contagiosum in an immunocompetent child is:

Natural resolution. ***Natural resolution*** - Molluscum contagiosum is a **self-limited viral infection** that typically resolves spontaneously within 6-12 months, or sometimes longer, even without intervention. - Given its benign nature and the potential for discomfort or scarring with aggressive treatments, **observational management** is often the most appropriate and effective "treatment" for extensive cases in immunocompetent children. *Oral acyclovir* - **Acyclovir** is an antiviral medication primarily effective against **herpes simplex virus (HSV)** and **varicella-zoster virus (VZV)**. - It has **no significant efficacy** against the **molluscum contagiosum virus (MCV)**, which belongs to the poxvirus family. *Cryotherapy* - **Cryotherapy** involves freezing the lesions with liquid nitrogen, which can be effective for individual lesions or a limited number of lesions. - For **extensive molluscum contagiosum**, cryotherapy would be **painful, time-consuming**, and potentially cause widespread scarring or hypopigmentation, making it impractical and not the most effective approach. *Topical imiquimod* - **Topical imiquimod** is an immune response modifier that stimulates the production of **cytokines**, such as interferon-alpha, which can help clear viral infections. - While it has been used off-label for molluscum, its efficacy is **variable**, and it can cause **significant local skin irritation** (redness, itching, burning), especially with extensive application, making it less suitable as the most effective treatment.

Q: A patient on steroids develops sudden onset painful vesicles in T4 dermatome. Best initial treatment is:

IV Acyclovir. ***IV Acyclovir*** - Patients on **steroids** are considered **immunocompromised**, and a sudden onset of painful vesicles in a dermatomal distribution strongly suggests **herpes zoster (shingles)** [1]. - In immunocompromised patients, **intravenous acyclovir** is the preferred initial treatment due to better bioavailability and more rapid systemic drug levels, helping to prevent complications like **postherpetic neuralgia** or disseminated disease [1]. *Oral Acyclovir* - While oral acyclovir is used for herpes zoster, it is generally less effective in **immunocompromised patients** due to lower bioavailability compared to IV administration. - The slower onset of action and lower peak plasma concentrations may not be sufficient to control the viral infection rapidly in this high-risk group. *Oral Valacyclovir* - **Valacyclovir** is a prodrug of acyclovir with improved oral bioavailability, making it a good option for immunocompetent patients with herpes zoster. - However, for **immunocompromised patients**, particularly those on steroids, **IV acyclovir** is still superior due to the need for rapid and high systemic drug levels to prevent severe complications [1]. *Topical Acyclovir* - **Topical acyclovir** is primarily used for **herpes simplex labialis (cold sores)** and has very limited efficacy for systemic viral infections like **herpes zoster**. - It does not achieve adequate systemic concentrations to treat the underlying viral replication or prevent complications in dermatomal zoster, especially in an immunocompromised individual.

Q: A child presents with grouped vesicles on an erythematous base on the buttocks. What is the most likely diagnosis?

Herpes simplex. ***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.

Q: What is the most commonly preferred first-line treatment for external genital warts caused by HPV?

Cryotherapy. **Cryotherapy** - **Cryotherapy** is a commonly preferred first-line treatment for external genital warts due to its effectiveness and good cosmetic outcomes [2], [3]. - It involves freezing the warts with **liquid nitrogen**, leading to their destruction [2], [3]. *5-FU* - **5-fluorouracil (5-FU)** cream is an antimetabolite that inhibits cell proliferation but is generally not a first-line treatment for external genital warts. - It can cause significant **local skin irritation, erosion, and pain**, making it less favorable for widespread use in this area. *Imiquimod* - **Imiquimod** is an immune response modifier that stimulates the production of cytokines but it's not considered as the first-line treatment [1]. - It requires multiple applications over several weeks and can cause **local inflammatory reactions** like erythema, itching, and burning [1]. *Podophyllin* - **Podophyllin** resin is an antimitotic agent but its use is limited due to potential systemic toxicity and local side effects like skin irritation [1]. - It is applied topically but must be washed off after a few hours to prevent severe reactions, and it is **contraindicated in pregnancy** [1].

Q: 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?

Herpes zoster. ***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.

Q: A 25-year-old woman presents with painful genital ulcers and tender inguinal lymphadenopathy. PCR confirms an HSV-2 infection. What is the treatment of choice?

Acyclovir. ***Acyclovir*** - **Acyclovir** is an **antiviral medication** that effectively inhibits the replication of HSV-2 by interfering with viral DNA synthesis, reducing the severity and duration of outbreaks. - It is the **treatment of choice** for genital **herpes simplex virus (HSV) infections**, helping to manage painful ulcers and prevent recurrences [1]. *Azithromycin* - **Azithromycin** is a **macrolide antibiotic** primarily used to treat bacterial infections, such as those caused by *Chlamydia trachomatis* [1] or respiratory pathogens. - It has **no antiviral activity** against HSV-2 and would therefore be ineffective for this infection. *Metronidazole* - **Metronidazole** is an **antibiotic and antiprotozoal medication** used for anaerobic bacterial infections and parasitic infections, such as trichomoniasis or bacterial vaginosis. - It possesses **no antiviral properties** against HSV-2 and is not indicated for the treatment of herpes. *Ciprofloxacin* - **Ciprofloxacin** is a **fluoroquinolone antibiotic** used to treat a wide range of bacterial infections, including urinary tract infections and certain sexually transmitted infections like chancroid. - It is **ineffective against viral infections** such as HSV-2, and its use in this context would be inappropriate.

Q: Which of the following sexually transmitted infections is most likely to present with vesicular lesions that ulcerate?

Genital herpes. ***Genital herpes*** - Caused by the **herpes simplex virus (HSV)**, it typically manifests as clusters of **painful vesicles** on an erythematous base. - These vesicles subsequently **ulcerate**, producing characteristic shallow, often painful sores. *Syphilis* - Primarily presents as a **painless chancre** (a single, firm ulcer) in its primary stage, not vesicular lesions. - Vesicular lesions are not a typical presentation of any stage of syphilis. *Chancroid* - Characterized by one or more **painful, soft ulcers with ragged, undermined borders** and a grayish base. - It does not present with an initial vesicular stage. *Lymphogranuloma venereum* - Initial lesion is often a **small, painless papule or a shallow ulcer** that often goes unnoticed. - The most prominent feature is usually painful **inguinal lymphadenopathy** (buboes), rather than vesicular eruptions.

Question 1

In a case of recurrent genital herpes with >6 episodes per year, which prophylactic regimen is most appropriate?

Accepted Answer

Valacyclovir 500mg daily

Answer

Acyclovir 400mg BD

Answer

Famciclovir 250mg BD

Answer

Acyclovir 200mg 5 times daily

Question 2

A patient with anogenital warts has not responded to conventional therapy after 3 months. Next best step is:

Accepted Answer

HIV testing

Answer

Switch to imiquimod

Answer

Continue same treatment longer

Answer

Biopsy lesion

Question 3

A 40-year-old man with HIV (CD4 350) presents with multiple flesh-colored papules on face, some with central umbilication. He works as a preschool teacher. Most appropriate management is:

Accepted Answer

No treatment needed

Answer

Topical imiquimod

Answer

Immediate cryotherapy

Answer

Leave of absence until resolution

Question 4

The most effective treatment for extensive molluscum contagiosum in an immunocompetent child is:

Accepted Answer

Natural resolution

Answer

Oral acyclovir

Answer

Cryotherapy

Answer

Topical imiquimod

Question 5

A patient on steroids develops sudden onset painful vesicles in T4 dermatome. Best initial treatment is:

Accepted Answer

IV Acyclovir

Answer

Oral Acyclovir

Answer

Oral Valacyclovir

Answer

Topical Acyclovir

Question 6

A child presents with grouped vesicles on an erythematous base on the buttocks. What is the most likely diagnosis?

Accepted Answer

Herpes simplex

Answer

Bullous impetigo

Answer

Dermatitis herpetiformis

Answer

Pemphigus

Question 7

What is the most commonly preferred first-line treatment for external genital warts caused by HPV?

Accepted Answer

Cryotherapy

Answer

5-FU

Answer

Imiquimod

Answer

Podophyllin

Question 8

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?

Accepted Answer

Herpes zoster

Answer

Contact dermatitis

Answer

Herpes simplex

Answer

Impetigo

Question 9

A 25-year-old woman presents with painful genital ulcers and tender inguinal lymphadenopathy. PCR confirms an HSV-2 infection. What is the treatment of choice?

Accepted Answer

Acyclovir

Answer

Azithromycin

Answer

Metronidazole

Answer

Ciprofloxacin

Question 10

Which of the following sexually transmitted infections is most likely to present with vesicular lesions that ulcerate?

Accepted Answer

Genital herpes

Answer

Syphilis

Answer

Chancroid

Answer

Lymphogranuloma venereum

Viral Skin Infections — MCQs

Viral Skin Infections — MCQs

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