Viral Skin Infections Practice Questions

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.

Q: A 30-year-old woman is diagnosed with genital herpes simplex virus infection by PCR analysis. Which type of lesion is most characteristic of this infection?

Vesicular. ***Vesicular*** - **Herpes simplex virus (HSV)** infections typically begin with the formation of painful, clustered **vesicles** (small, fluid-filled blisters) on an erythematous base. - These vesicles are characteristic of the primary stage of a herpetic outbreak before they rupture to form ulcers. *Pustular* - **Pustules** are elevated lesions filled with pus, often associated with bacterial infections or certain inflammatory conditions like acne. - While secondary bacterial infections can occur in HSV lesions, pustules are not the primary or most characteristic presentation of an uncomplicated HSV outbreak. *Maculopapular* - **Maculopapular rashes** consist of both flat, discolored lesions (**macules**) and raised, solid lesions (**papules**), commonly seen in viral exanthems or drug reactions. - This morphology is not typical for the localized, vesicular presentation of herpes simplex virus. *Erosive* - **Erosions** are superficial skin defects resulting from the loss of the epidermis, often occurring *after* vesicles rupture. - While genital herpes lesions eventually become erosive ulcers, the most characteristic *initial* lesion formed by the virus itself is the vesicle, which then *progresses* to an erosion.

Q: A 60-year-old man presents with a painful, vesicular rash in a dermatomal distribution on his right thorax. What is the most likely diagnosis?

Herpes zoster. ***Herpes zoster*** - The classic presentation of **painful, vesicular rash** in a **dermatomal distribution** is highly indicative of **herpes zoster**, also known as shingles. - This condition is caused by the reactivation of the **varicella-zoster virus (VZV)**, which lies dormant in sensory ganglia after a primary chickenpox infection. *Herpes simplex* - While herpes simplex causes **vesicular lesions**, they typically occur in localized clusters (e.g., oral or genital) and do not follow a **dermatomal pattern**. - Recurrent outbreaks are common, but the rash is generally less extensive and painful than in zoster. *Contact dermatitis* - **Contact dermatitis** is an inflammatory skin condition caused by exposure to irritants or allergens, resulting in an **erythematous, pruritic rash**, sometimes with vesicles. - However, it does not typically present with a **dermatomal distribution** and the pain is usually less prominent than the itching. *Impetigo* - **Impetigo** is a bacterial skin infection characterized by **honey-crusted lesions** and superficial blisters, commonly seen in children. - It is not typically painful, rarely follows a **dermatomal pattern**, and is not initially vesicular in the same way as zoster.

Q: A 40-year-old male presents with multiple vesicles on his penis that later ulcerate. Which test is most likely to confirm the diagnosis?

PCR for HSV. PCR for HSV - PCR (Polymerase Chain Reaction) for herpes simplex virus (HSV) is the most sensitive and specific test for confirming an active HSV infection, especially in the presence of vesicular or ulcerative lesions [1]. - It detects the viral DNA directly from the lesion fluid, providing a definitive diagnosis of genital herpes [2]. Tzanck smear - A Tzanck smear can reveal multinucleated giant cells and acantholytic cells, which are characteristic of herpes simplex virus (HSV) or varicella-zoster virus (VZV) infections. - However, it has lower sensitivity and specificity compared to PCR, as it does not distinguish between HSV and VZV and can produce false negatives. Viral culture - Viral culture was historically the gold standard for HSV diagnosis and can confirm the presence of live virus [1]. - However, it has lower sensitivity than PCR, especially in later stages of lesion evolution or with crusted lesions, and can take longer to yield results [2]. Serology for HSV antibodies - Serology for HSV antibodies detects the presence of IgG or IgM antibodies to HSV, indicating past exposure or primary infection [3]. - While useful for diagnosing recurrent or past infections and differentiating between HSV-1 and HSV-2, it does not confirm an acute, active infection causing current lesions, as antibodies may take weeks to appear after initial infection [2].

Question 1

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 2

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 3

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 4

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 5

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 6

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 7

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

Question 8

A 30-year-old woman is diagnosed with genital herpes simplex virus infection by PCR analysis. Which type of lesion is most characteristic of this infection?

Accepted Answer

Vesicular

Answer

Pustular

Answer

Maculopapular

Answer

Erosive

Question 9

A 60-year-old man presents with a painful, vesicular rash in a dermatomal distribution on his right thorax. What is the most likely diagnosis?

Accepted Answer

Herpes zoster

Answer

Herpes simplex

Answer

Contact dermatitis

Answer

Impetigo

Question 10

A 40-year-old male presents with multiple vesicles on his penis that later ulcerate. Which test is most likely to confirm the diagnosis?

Accepted Answer

PCR for HSV

Answer

Tzanck smear

Answer

Viral culture

Answer

Serology for HSV antibodies

Viral Skin Infections — MCQs

Viral Skin Infections — MCQs

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