Viral Skin Infections Practice Questions

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: 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.

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: A teenager presented with a skin lesion that appeared as a thin, oval plaque with a fine collarette of scale located inside the periphery of the plaque. Pityriasis rosea is diagnosed. All of the following are characteristic of pityriasis rosea, except:

Lower respiratory infection. ***Lower respiratory infection*** - **Pityriasis rosea** is a self-limiting inflammatory skin condition, and while patients may experience mild prodromal symptoms like fatigue and malaise, a **lower respiratory infection** is not a characteristic feature or complication. - The disease is primarily a mucocutaneous eruption with no typical association with pulmonary involvement. *Herald patch* - The **herald patch** is the initial, solitary, larger lesion that precedes the generalized rash in pityriasis rosea. - It often appears a few days to two weeks before the widespread eruption and is a key diagnostic feature. *Moderate itching* - **Pruritus**, or itching, is a common symptom associated with pityriasis rosea, ranging from mild to moderate. - While not universally present or severe, it is a characteristic complaint for many patients. *Low grade fever* - Many patients with pityriasis rosea experience mild, **flu-like prodromal symptoms**, including a **low-grade fever**, malaise, and headache. - These symptoms typically precede the skin eruption and resolve as the rash develops.

Q: A 35-year-old professional businesswoman notices the appearance of several hyperkeratotic, well-demarcated growths on the palmar surface of her index finger and on her toe. They do not change in size and cause her only minimal discomfort. A biopsy of one of the lesions, viewed at 40x magnification, is shown. Which of the following viruses is the most likely etiologic agent?

HPV. ***HPV*** - The clinical description of **hyperkeratotic**, **well-demarcated growths** on the palmar surface and toe is highly characteristic of **warts** (verrucae), which are caused by **Human Papillomavirus (HPV)**. - The biopsy likely shows **koilocytes** (HPV-infected keratinocytes with perinuclear vacuolization), which are pathognomonic for HPV infection in the skin. *Adenovirus* - Adenovirus typically causes **respiratory tract infections**, **conjunctivitis**, or **gastroenteritis**, and less commonly skin lesions. - Skin manifestations from adenovirus are usually non-specific rashes, not hyperkeratotic growths like those described. *Molluscum contagiosum virus* - **Molluscum contagiosum** is caused by the **Molluscum contagiosum virus (MCV)** and presents as **umbilicated papules**, differing morphologically from the described hyperkeratotic warts. - Histologically, molluscum contagiosum lesions are characterized by **Molluscum bodies** (large eosinophilic cytoplasmic inclusions), which are different from koilocytes. *Echovirus* - Echoviruses are enteroviruses primarily associated with a wide range of syndromes including **aseptic meningitis**, **exanthems (rashes)**, and **respiratory illnesses**. - They do not typically cause localized, hyperkeratotic skin growths like warts.

Q: Which of the following infections can cause genital ulcers?

Herpes simplex virus (HSV). ***Herpes simplex virus (HSV)*** - HSV causes **painful, vesicular lesions** on the genitals that can rupture to form **ulcers** [1], [2]. - These infections are known for their recurrent nature and are one of the most common causes of **genital ulcers** [1], [2]. *Human papillomavirus (HPV)* - HPV primarily causes **genital warts** (condylomata acuminata), which are **flesh-colored, cauliflower-like growths**, not ulcers. - While some high-risk HPV types can lead to cervical or other anogenital cancers, they do not directly present as ulcers. *Syphilis (Treponema pallidum)* - Syphilis causes a **painless chancre** in its primary stage, which is a type of ulcer [1]. - However, the question asks which of the given options *can* cause genital ulcers, and HSV is a direct and common cause with the classic presentation of multiple painful ulcers [1]. *Human immunodeficiency virus (HIV)* - HIV itself does not directly cause genital ulcers. - However, it can increase an individual's susceptibility to other infections that do cause ulcers, or worsen the presentation of existing ulcer-causing STIs.

Question 1

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 2

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 3

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 4

Which area is typically not involved in a chickenpox rash?

Accepted Answer

Palms and soles

Answer

Trunk

Answer

Axilla

Answer

Back

Question 5

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 6

What is the most common trigger associated with erythema multiforme?

Accepted Answer

Herpes simplex

Answer

Mycoplasma pneumoniae

Answer

TB

Answer

Drugs

Question 7

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 8

A teenager presented with a skin lesion that appeared as a thin, oval plaque with a fine collarette of scale located inside the periphery of the plaque. Pityriasis rosea is diagnosed. All of the following are characteristic of pityriasis rosea, except:

Accepted Answer

Lower respiratory infection

Answer

Moderate itching

Answer

Low grade fever

Answer

Herald patch

Question 9

A 35-year-old professional businesswoman notices the appearance of several hyperkeratotic, well-demarcated growths on the palmar surface of her index finger and on her toe. They do not change in size and cause her only minimal discomfort. A biopsy of one of the lesions, viewed at 40x magnification, is shown. Which of the following viruses is the most likely etiologic agent?

Accepted Answer

HPV

Answer

Adenovirus

Answer

Molluscum contagiosum virus

Answer

Echovirus

Question 10

Which of the following infections can cause genital ulcers?

Accepted Answer

Herpes simplex virus (HSV)

Answer

Syphilis (Treponema pallidum)

Answer

Human papillomavirus (HPV)

Answer

Human immunodeficiency virus (HIV)

Viral Skin Infections — MCQs

Viral Skin Infections — MCQs

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