Viral Skin Infections Practice Questions

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: Identify the infectious cause of erythema multiforme in the image.

Herpes simplex virus (HSV). ***Herpes simplex virus (HSV)*** - **Herpes simplex virus (HSV)** is the most common infectious trigger for **erythema multiforme (EM)**, especially recurrent forms. - The rash typically appears within days or weeks following an HSV outbreak, often presenting with characteristic **target lesions**. *Staphylococcus aureus* - **Staphylococcus aureus** is a common cause of skin infections like **impetigo** or **cellulitis**, but it is not a primary trigger for erythema multiforme. - While it can cause systemic inflammation, its association with EM is indirect and rare, unlike viral infections. *Mycobacterium tuberculosis* - **Mycobacterium tuberculosis** is the causative agent of tuberculosis, a chronic bacterial infection primarily affecting the lungs. - It is not directly associated with **erythema multiforme**; rather, it can be linked to other cutaneous manifestations such as **erythema nodosum**. *Epstein-Barr virus (EBV)* - While **Epstein-Barr virus (EBV)** can cause various skin rashes, including those associated with **infectious mononucleosis**, it is a far less common cause of **erythema multiforme** compared to HSV. - EM associated with EBV is typically seen in the context of primary infection, not as a recurring phenomenon.

Q: What is the most probable diagnosis of a child who presents with white umbilicated lesions on the face?

Molluscum contagiosum. ***Molluscum contagiosum*** - The description of **white, umbilicated lesions** is a classic presentation of **molluscum contagiosum**, a common viral skin infection in children. - These lesions are typically **dome-shaped papules** with a central depression, often appearing on the face, trunk, and extremities. *Herpes simplex infection* - Herpes simplex typically presents as **vesicles on an erythematous base** that can later crust over, which is different from the described umbilicated lesions. - It often causes **painful, recurrent outbreaks** and may be associated with systemic symptoms like fever. *Erythema toxicum neonatorum* - This is a benign rash seen in newborns, characterized by **blotchy red spots** with central papules or pustules, not white umbilicated lesions. - It usually appears within the first few days of life and resolves spontaneously. *Human papilloma virus infection* - HPV typically causes **warts**, which are rough, verrucous papules, rather than smooth, umbilicated lesions. - The appearance of warts can vary significantly but generally lacks the central umbilication seen in molluscum.

Q: Which of the following conditions is caused by Human Papillomavirus (HPV)?

Condyloma acuminata (genital warts). ***Condyloma acuminata (genital warts)*** - **Condyloma acuminata** are fleshy, exophytic lesions caused by Human Papillomavirus (**HPV**), particularly types 6 and 11. - HPV infection of the anogenital region leads to characteristic **genital warts**, which can be single or multiple, and range from small papules to large cauliflower-like masses. *Condylomata lata (associated with syphilis)* - **Condylomata lata** are broad-based, raised, gray-white lesions found in moist intertriginous areas, a manifestation of **secondary syphilis**. - They are highly infectious but are caused by the bacterium **_Treponema pallidum_**, not HPV. *Chancre (associated with syphilis)* - A **chancre** is a firm, painless ulcer with raised borders that appears at the site of inoculation during the **primary stage of syphilis**. - This lesion is also caused by the spirochete **_Treponema pallidum_**. *Bubo (associated with bacterial infections)* - A **bubo** is a painful, swollen, inflamed **lymph node**, typically in the groin, resulting from bacterial infections like **lymphogranuloma venereum** or **chancroid**. - It is caused by bacterial pathogens such as _Chlamydia trachomatis_ serovars L1-L3 or _Haemophilus ducreyi_, not HPV.

Question 1

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 2

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

Accepted Answer

Pityriasis rosea

Answer

Psoriasis

Answer

Lichen planus

Answer

Eczema

Question 3

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 4

What type of lesion is characteristic of molluscum contagiosum?

Accepted Answer

Papules

Answer

Vesicles

Answer

Nodules

Answer

Pustules

Question 5

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 6

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 7

What is the most common identifiable precipitant of erythema multiforme?

Accepted Answer

HSV

Answer

Idiopathic

Answer

Drugs

Answer

TB

Question 8

Identify the infectious cause of erythema multiforme in the image.

Accepted Answer

Herpes simplex virus (HSV)

Answer

Staphylococcus aureus

Answer

Mycobacterium tuberculosis

Answer

Epstein-Barr virus (EBV)

Question 9

What is the most probable diagnosis of a child who presents with white umbilicated lesions on the face?

Accepted Answer

Molluscum contagiosum

Answer

Herpes simplex infection

Answer

Erythema toxicum neonatorum

Answer

Human papilloma virus infection

Question 10

Which of the following conditions is caused by Human Papillomavirus (HPV)?

Accepted Answer

Condyloma acuminata (genital warts)

Answer

Condylomata lata (associated with syphilis)

Answer

Chancre (associated with syphilis)

Answer

Bubo (associated with bacterial infections)

Viral Skin Infections — MCQs

Viral Skin Infections — MCQs

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