Viral Skin Infections Practice Questions

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: 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].

Q: Which skin condition is often triggered by an upper respiratory tract infection?

Pityriasis rosea. ***Pityriasis rosea*** - This condition is often preceded by an **upper respiratory tract infection** (typically viral), suggesting a possible viral etiology, though the exact cause is unknown. - It typically presents with a **herald patch** followed by smaller, oval, pinkish-red patches with fine scales, often arranged in a **Christmas tree pattern** on the trunk. - The prodromal viral-like illness makes this the classic condition associated with URTI. *Psoriasis* - While **guttate psoriasis** can be triggered by **bacterial streptococcal pharyngitis** (not typical viral URTI), general psoriasis is a **chronic autoimmune** condition with genetic predispositions. - Psoriasis is characterized by **erythematous plaques** with silvery scales, commonly affecting extensor surfaces, the scalp, and nails. - The trigger for guttate psoriasis is specifically bacterial (strep throat), not the viral URTIs typically associated with pityriasis rosea. *Lichen planus* - This is an **inflammatory skin condition** that affects the skin, hair, nails, and mucous membranes, with no clear association with an acute URTI. - It typically presents with **pruritic, polygonal, planar, purple papules and plaques** (the "6 Ps"). *Eczema* - Eczema (or **atopic dermatitis**) is a chronic, relapsing inflammatory skin condition associated with a compromise in the skin barrier and often linked to allergies or asthma. - It is characterized by **itchy, dry, red, and inflamed patches of skin**, and is not typically triggered by an URTI.

Q: A 60-year-old man presents with a vesicular rash in a dermatomal distribution on the chest. What is the most likely complication if left untreated?

Postherpetic neuralgia. ***Postherpetic neuralgia*** - This is the most common and debilitating complication of **herpes zoster**, characterized by persistent pain in the affected dermatome for months or even years after the rash resolves. - The risk of **postherpetic neuralgia** increases with age and is particularly common in individuals over 60. *Cellulitis* - While possible, **bacterial superinfection** leading to cellulitis is a secondary complication, not the most likely long-term complication of untreated herpes zoster itself. - Cellulitis would involve localized inflammation and warmth, distinct from the neuropathic pain of postherpetic neuralgia. *Lymphadenopathy* - **Regional lymphadenopathy** is a common acute finding during the active phase of herpes zoster due to immune response to the viral infection. - It is not considered a long-term complication of untreated zoster; rather, it's a transient symptom. *Systemic lupus erythematosus* - This is an **autoimmune disease** with a wide range of systemic manifestations and no direct causal link to untreated herpes zoster. - There is no evidence to suggest that untreated herpes zoster leads to the development of SLE.

Q: What type of lesion is characteristic of molluscum contagiosum?

Papules. ***Papules*** - Molluscum contagiosum typically presents as **small, flesh-colored, dome-shaped papules** with a characteristic **umbilicated center**. - These lesions are caused by a **poxvirus** and are highly contagious. *Vesicles* - **Vesicles** are small, fluid-filled blisters (less than 1 cm in diameter), characteristic of conditions like **herpes simplex** or **chickenpox**. - Molluscum contagiosum lesions are solid rather than fluid-filled. *Nodules* - **Nodules** are larger, deeper solid lesions (greater than 1 cm), often extending into the dermis or subcutis. - While molluscum lesions can be palpated, their characteristic size and appearance are generally smaller, making "papule" a more precise description. *Pustules* - **Pustules** are small, elevated lesions containing **pus**, typically seen in bacterial infections like **folliculitis** or **acne**. - Molluscum contagiosum lesions do not contain pus, differentiating them from pustules.

Question 1

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 2

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 3

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 4

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 5

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 6

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 7

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

Question 8

Which skin condition is often triggered by an upper respiratory tract infection?

Accepted Answer

Pityriasis rosea

Answer

Psoriasis

Answer

Lichen planus

Answer

Eczema

Question 9

A 60-year-old man presents with a vesicular rash in a dermatomal distribution on the chest. What is the most likely complication if left untreated?

Accepted Answer

Postherpetic neuralgia

Answer

Cellulitis

Answer

Lymphadenopathy

Answer

Systemic lupus erythematosus

Question 10

What type of lesion is characteristic of molluscum contagiosum?

Accepted Answer

Papules

Answer

Vesicles

Answer

Nodules

Answer

Pustules

Viral Skin Infections — MCQs

Viral Skin Infections — MCQs

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