Viral Skin Infections Practice Questions

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.

Q: A 30-year-old male presents with painful ulcers on the glans penis. A Tzanck smear reveals multinucleated giant cells. What is the most likely diagnosis?

Genital herpes. ***Genital herpes*** - The presence of **painful ulcers** on the glans penis is characteristic of genital herpes [1], [3]. - A **Tzanck smear** demonstrating **multinucleated giant cells** is a classic finding for **herpes simplex virus (HSV)** infection. *Syphilis* - Typically presents as a **painless chancre** in its primary stage, which is different from the painful ulcers described. - Diagnosis involves **darkfield microscopy** or **serological tests** (e.g., RPR, VDRL, FTA-ABS). *Chancroid* - Characterized by **painful, ragged-edged ulcers** with a **gray base**, often accompanied by **tender inguinal lymphadenopathy** [2]. - Diagnosis is usually clinical or by **culture** of *Haemophilus ducreyi*; a Tzanck smear does not reveal multinucleated giant cells. *Lymphogranuloma venereum* - Begins with a small, **painless ulcer or papule** that often goes unnoticed, followed by significant and **painful regional lymphadenopathy** (buboes) [2]. - Caused by specific strains of *Chlamydia trachomatis*, and diagnosis involves serology or PCR, not Tzanck smear findings.

Q: A 65-year-old patient presents with a painful unilateral rash. Identify the condition shown in the image.

Image of Herpes zoster. ***Image of Herpes zoster*** - This image displays a characteristic **unilateral rash** with **vesicles** in a **dermatomal distribution**, which is pathognomonic for **herpes zoster** (shingles). - The rash is typically painful and follows the path of a specific **nerve root**, often in older adults or immunocompromised individuals. *Image of Small pox* - **Smallpox** presents with deeply embedded **umbilicated pustules** that are typically all in the same stage of development and *not* dermatomal. - The rash of smallpox is more widespread and typically starts on the face and extremities, spreading to the trunk. *Image of Chicken pox* - **Chickenpox** (varicella) rash is characterized by lesions in different stages of development (**pleomorphic**), including macules, papules, vesicles, and scabs, scattered over the entire body, without a dermatomal pattern. - The vesicles of chickenpox are often described as "dewdrops on a rose petal" and are more superficial than those seen in herpes zoster. *Image of Atopic dermatitis* - **Atopic dermatitis** (eczema) typically presents as red, itchy, inflamed patches of skin with **dryness**, scaling, and sometimes lichenification, often in flexural areas like the elbows and knees. - The lesions are usually chronic and highly pruritic, but they do not form vesicles in a dermatomal pattern as seen here.

Q: What is the most common identifiable precipitant of erythema multiforme?

HSV. ***HSV*** - **Herpes simplex virus (HSV)** infection is the most common identifiable cause of erythema multiforme, particularly the recurrent form. - The rash typically appears **1-3 weeks after an HSV outbreak**, suggesting an **immune-mediated hypersensitivity reaction** to viral antigens. - HSV-1 (oral herpes) is more commonly associated than HSV-2. *Idiopathic* - While a significant portion of erythema multiforme cases are **idiopathic** (no identifiable cause found), the question asks for the most common *identifiable* precipitant. - By definition, idiopathic means the cause cannot be identified, so it doesn't answer the question. *Drugs* - **Drugs** are an important cause of erythema multiforme, but they more commonly cause severe variants like **Stevens-Johnson syndrome (SJS)** and **toxic epidermal necrolysis (TEN)**. - For classic erythema multiforme minor, **HSV is a more frequent trigger** than medications. - Common drug culprits include NSAIDs, sulfonamides, anticonvulsants, and antibiotics. *TB* - **Tuberculosis (TB)** can cause various dermatological manifestations such as **erythema induratum** (Bazin's disease) or **lupus vulgaris**. - TB is **not a recognized precipitant** of erythema multiforme.

Q: Which of the following was historically used as an adjunctive systemic treatment for genital warts but is now rarely employed due to limited efficacy and significant side effects?

Interferon alpha. ***Interferon alpha*** - **Interferon alpha** was historically used as an adjunctive treatment for **genital warts**, primarily due to its **antiviral** and **immunomodulatory properties**, though its efficacy was limited and it caused significant side effects. - It works by stimulating the host immune response against the **human papillomavirus (HPV)**, which causes genital warts. *Acyclovir* - **Acyclovir** is an **antiviral medication** used predominantly for **herpes simplex virus (HSV)** infections, such as genital herpes, and not for genital warts caused by HPV. - Its mechanism of action involves inhibiting viral DNA replication, which is specific to herpesviruses. *Podophyllin* - **Podophyllin** is a **topical cytotoxic agent** that induces necrosis in genital warts and is still used today. - While effective, it is applied directly to the warts and is not administered systemically like **interferon alpha** was. *Minocycline* - **Minocycline** is a **tetracycline antibiotic** used to treat bacterial infections, such as those caused by *Acne vulgaris* or *Chlamydia*. - It has no antiviral activity against **HPV** and therefore is not used for genital warts.

Question 1

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 2

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 3

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 4

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

Accepted Answer

Pityriasis rosea

Answer

Psoriasis

Answer

Lichen planus

Answer

Eczema

Question 5

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 6

What type of lesion is characteristic of molluscum contagiosum?

Accepted Answer

Papules

Answer

Vesicles

Answer

Nodules

Answer

Pustules

Question 7

A 30-year-old male presents with painful ulcers on the glans penis. A Tzanck smear reveals multinucleated giant cells. What is the most likely diagnosis?

Accepted Answer

Genital herpes

Answer

Syphilis

Answer

Chancroid

Answer

Lymphogranuloma venereum

Question 8

A 65-year-old patient presents with a painful unilateral rash. Identify the condition shown in the image.

Accepted Answer

Image of Herpes zoster

Answer

Image of Small pox

Answer

Image of Chicken pox

Answer

Image of Atopic dermatitis

Question 9

What is the most common identifiable precipitant of erythema multiforme?

Accepted Answer

HSV

Answer

Idiopathic

Answer

Drugs

Answer

TB

Question 10

Which of the following was historically used as an adjunctive systemic treatment for genital warts but is now rarely employed due to limited efficacy and significant side effects?

Accepted Answer

Interferon alpha

Answer

Acyclovir

Answer

Minocycline

Answer

Podophyllin

Viral Skin Infections — MCQs

Viral Skin Infections — MCQs

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