Viral Skin Infections Practice Questions

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: 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.

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: A patient presents with painful vesicular eruptions on one side of the body. What is the most likely diagnosis based on the clinical image?

Herpes zoster. ***Herpes zoster*** - The image displays characteristic **vesicular lesions** grouped together on an erythematous base, typically following a **dermatomal distribution**, which is classic for herpes zoster (shingles). - These lesions often cause significant pain and are due to the **reactivation of the varicella-zoster virus**. *Smallpox* - Smallpox lesions are typically **deep-seated, firm, round pustules** that are all in the same stage of development. - While smallpox also features vesicular lesions, their appearance and distribution are distinct from the clustered, dermatomal pattern seen in the image. *Chickenpox* - Chickenpox presents as a generalized rash with lesions at **various stages of development** (macules, papules, vesicles, scabs), often described as a "dewdrop on a rose petal." - Unlike the localized, dermatomal pattern of herpes zoster, chickenpox lesions are typically **widespread** over the body. *Atopic dermatitis* - Atopic dermatitis typically manifests as **erythematous, scaly, intensely itchy patches or plaques**, often in areas like the flexural creases. - It does not present with the characteristic **vesicular, grouped lesions in a dermatomal pattern** seen in the image.

Q: A child with a family history of allergies presents with pruritus on the face and convexities, followed by the development of numerous umbilicated vesicles that become pustular, hemorrhagic, and crusted. After two days, the child develops a high fever and lymphadenopathy. What is the most likely diagnosis?

Herpes simplex virus infection. ***Herpes simplex virus infection (Eczema herpeticum)*** - The presentation of **numerous umbilicated vesicles** that become **pustular, hemorrhagic, and crusted** in a child with atopic dermatitis is pathognomonic of **eczema herpeticum** (Kaposi varicelliform eruption). - **High fever** and **lymphadenopathy** developing after two days indicate systemic HSV infection, a characteristic feature of eczema herpeticum. - This is a **dermatological emergency** requiring immediate antiviral therapy (acyclovir) as it can progress to disseminated HSV infection with high morbidity. - The distribution on **face and convexities** matches typical atopic dermatitis sites where HSV superinfection occurs. *Eczema vaccinatum* - While clinically similar to eczema herpeticum, eczema vaccinatum is caused by **vaccinia virus** (smallpox vaccine complication). - This condition is **historically important but extremely rare today** since routine smallpox vaccination was discontinued in the 1970s-1980s. - In modern clinical practice and contemporary medical exams, eczema herpeticum (HSV) is the relevant diagnosis for this presentation. *Secondary infected atopic dermatitis* - Bacterial superinfections (usually *Staphylococcus aureus* or *Streptococcus*) typically produce **honey-colored crusts** (impetigo) or weeping, purulent lesions. - They do **not** produce the characteristic **umbilicated vesicles** described in this case. - The rapid, widespread vesicular eruption with systemic symptoms points to viral rather than bacterial etiology. *Molluscum contagiosum* - Presents as **discrete, pearly, dome-shaped umbilicated papules** that are chronic and typically asymptomatic. - Does **not** cause acute systemic symptoms like high fever and lymphadenopathy. - Does **not** progress to pustular, hemorrhagic, and crusted lesions as described in this case.

Q: Which area is typically not involved in a chickenpox rash?

Palms and soles. ***Palms and soles*** - The chickenpox rash, caused by the **varicella-zoster virus**, typically spares the palms and soles. - Chickenpox exhibits a characteristic **centripetal distribution** (center-predominant), with lesions most numerous on the trunk and progressively fewer on the extremities. - **Sparing of palms and soles** is a classic differentiating feature from other viral exanthems like hand-foot-and-mouth disease. *Trunk* - The **trunk** is usually the **most heavily involved area** in a chickenpox rash, with lesions often appearing first and being most numerous here. - This is the hallmark of the characteristic **centripetal distribution** of the rash. *Axilla* - The **axilla** is a common site for chickenpox lesions due to its location on the trunk and the presence of **warm, moist skin folds** that can favor lesion development. - The rash tends to be widespread, making secondary sites like the axilla commonly involved. *Back* - The **back** is a major part of the trunk and is therefore extensively involved in a chickenpox rash. - The rash often starts on the trunk and spreads outwards, ensuring significant involvement of the back.

Q: A man with pain during defecation, no gastrointestinal symptoms, and ulcers extending into the anal canal. Diagnosis?

Genital herpes. Herpes simplex virus (HSV) infection of the anal canal is characterized by lesions that present as painful ulcers [1]. Direct extension into the anal canal is common in individuals with receptive anal intercourse or autoinoculation, often causing symptoms such as anal or rectal pain [1]. CMV proctitis typically causes more diffuse inflammation, often with bloody stools, diarrhea, and abdominal pain, which are not described in this case. While CMV can cause ulcers, they are usually shallow and often associated with immunocompromised states. Gonococcal proctitis often presents with purulent anal discharge, rectal pain, itching, and tenesmus, but typically without deep ulcerations. HIV infection can cause various anorectal complications, including aphthous ulcers, but isolated anal ulcers and defecation pain would prompt investigation into sexually transmitted infections like herpes as a more direct cause.

Q: What does a Tzanck smear in varicella-zoster virus infection typically show?

Multinucleated giant cells. ***Multinucleated giant cells*** - A Tzanck smear identifies **multinucleated giant cells** with intranuclear inclusions, which are characteristic **cytopathic effects** of herpesviruses like VZV [1]. - These cells result from the fusion of infected keratinocytes, a hallmark finding in **herpes simplex** and **varicella-zoster infections** [1]. *Acantholytic cells* - Acantholytic cells are seen in conditions like **pemphigus vulgaris**, where there is loss of cell-to-cell adhesion between keratinocytes, leading to intraepidermal blistering. - While VZV can cause blistering, the primary cytological finding on Tzanck smear is not acantholysis but rather the presence of multinucleated cells. *Epidermal spongiosis* - Spongiosis refers to **intercellular edema** of epidermal cells, leading to widening of the intercellular spaces, typically seen in **eczematous dermatoses** [1]. - This finding is not specific to viral infections and does not represent the characteristic cytopathic effect of VZV on a Tzanck smear. *Necrotic cells* - Necrotic cells, or dead cells, are a general finding in many inflammatory and infectious processes where tissue damage occurs. - While VZV infection can lead to cell necrosis, the presence of isolated necrotic cells is not the specific, diagnostic feature for VZV on a Tzanck smear. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 366-367.

Q: What is the most common trigger associated with erythema multiforme?

Herpes simplex. ***Herpes simplex*** - **Herpes simplex virus (HSV)** is the most common precipitating factor for **erythema multiforme**, accounting for **50-60% of identifiable cases**, particularly the recurrent form. - The rash typically appears **10-14 days after an HSV outbreak**, suggesting an immune-mediated reaction. - **HSV-1** is more commonly implicated than HSV-2. *Mycoplasma pneumoniae* - **Mycoplasma pneumoniae** is the **second most common infectious trigger** for erythema multiforme, especially in children and young adults. - EM associated with Mycoplasma typically occurs during or after respiratory infection. - However, it is still less common than HSV as a trigger. *TB* - **Tuberculosis (TB)** is not typically associated with erythema multiforme. - While other infections can trigger erythema multiforme, TB is rarely implicated. *Drugs* - **Drug reactions** are a recognized cause of erythema multiforme, but they are less common than HSV infection as a trigger. - Certain medications like **sulfonamides, anticonvulsants, NSAIDs, and penicillins** are among the drugs that can induce erythema multiforme.

Question 1

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 2

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)

Question 3

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 4

Which of the following statements about herpes zoster complications is incorrect?

Accepted Answer

Postherpetic neuralgia is the most common complication of herpes zoster

Answer

Chickenpox and herpes zoster are caused by the same virus (VZV)

Answer

Herpes zoster typically occurs in a dermatomal distribution

Answer

Chickenpox vaccination prevents both primary varicella and herpes zoster reactivation completely

Question 5

A patient presents with painful vesicular eruptions on one side of the body. What is the most likely diagnosis based on the clinical image?

Accepted Answer

Herpes zoster

Answer

Smallpox

Answer

Chickenpox

Answer

Atopic dermatitis

Question 6

A child with a family history of allergies presents with pruritus on the face and convexities, followed by the development of numerous umbilicated vesicles that become pustular, hemorrhagic, and crusted. After two days, the child develops a high fever and lymphadenopathy. What is the most likely diagnosis?

Accepted Answer

Herpes simplex virus infection

Answer

Secondary infected atopic dermatitis

Answer

Molluscum contagiosum

Answer

Eczema vaccinatum

Question 7

Which area is typically not involved in a chickenpox rash?

Accepted Answer

Palms and soles

Answer

Trunk

Answer

Axilla

Answer

Back

Question 8

A man with pain during defecation, no gastrointestinal symptoms, and ulcers extending into the anal canal. Diagnosis?

Accepted Answer

Genital herpes

Answer

Cytomegalovirus (CMV)

Answer

Gonococcal infection

Answer

HIV infection

Question 9

What does a Tzanck smear in varicella-zoster virus infection typically show?

Accepted Answer

Multinucleated giant cells

Answer

Acantholytic cells

Answer

Epidermal spongiosis

Answer

Necrotic cells

Question 10

What is the most common trigger associated with erythema multiforme?

Accepted Answer

Herpes simplex

Answer

Mycoplasma pneumoniae

Answer

TB

Answer

Drugs

Viral Skin Infections — MCQs

Viral Skin Infections — MCQs

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