Viral Skin Infections Practice Questions

Q: A young man presented with painful vesicular lesions distributed along a dermatomal pattern on one side of his body. What is the likely diagnosis?

Herpes Zoster. ***Herpes Zoster*** - This condition is characterized by a **unilateral rash** that respects the **dermatomal distribution**, meaning it follows the path of a single nerve. - The lesions are typically **painful vesicles** and crusts, often associated with a burning sensation due to reactivation of the **varicella-zoster virus** (chickenpox virus). *Lymphangioma circumscriptum* - This is a rare **lymphatic malformation** presenting as clusters of **vesicles** or papules, often described as 'frog spawn' or 'tapioca pudding' in appearance. - While it can be painful, it usually does not follow a dermatomal pattern and is a congenital condition, not an acute viral eruption. *Molluscum contagiosum* - This is a viral skin infection producing small, firm, **umbilicated papules** that are typically flesh-colored or pearly. - While contagious, these lesions are generally **asymptomatic** and do not present with the acute pain, blistering, or dermatomal distribution characteristic of herpes zoster. *Herpes simplex* - This infection causes localized clusters of painful **vesicles** on an erythematous base, most commonly around the mouth (cold sores) or genitals. - Unlike herpes zoster, herpes simplex lesions typically recur in the same small area and do **not follow a dermatomal distribution**.

Q: A 25-year-old woman presents for STI screening. She reports consistent condom use with her partner. Which of the following STIs is least effectively prevented by proper condom use?

HPV. ***HPV*** - **Human Papillomavirus** is primarily transmitted through skin-to-skin contact, making it difficult to prevent even with consistent condom use [1]. - Condoms may not cover all infected skin areas, allowing for transmission from areas like the **scrotum** or **perineum** [1]. *Chlamydia* - **Chlamydia trachomatis** is a bacterial infection primarily transmitted through **genital fluid exchange**, which is largely prevented by condoms. - Consistent and correct condom use significantly reduces the risk of transmission. *Gonorrhea* - **Neisseria gonorrhoeae** is a bacterial infection transmitted through **mucous membrane contact** and **genital fluids**, effectively blocked by condoms. - Condoms serve as a reliable barrier against the transmission of this bacterium. *HIV* - **Human Immunodeficiency Virus** is transmitted through **bodily fluids** including semen and vaginal fluid; condoms are highly effective in preventing this exchange. - When used correctly and consistently, condoms are a critical tool in preventing HIV transmission. *Hepatitis B* - **Hepatitis B virus (HBV)** is transmitted through **blood** and **bodily fluids**, including sexual contact. - Condoms provide a significant physical barrier against the exchange of these fluids, thus reducing transmission risk.

Q: A 35-year-old man presents with burning penile lesions 3 days after unprotected intercourse. He has no prior history of similar lesions. Which of the following best differentiates primary from recurrent HSV infection?

Systemic symptoms and bilateral lymphadenopathy. Systemic symptoms and bilateral lymphadenopathy - **Primary HSV infection** often presents with noticeable **systemic symptoms** such as fever, malaise, myalgia, and bilateral inguinal lymphadenopathy [1], [2]. - These systemic features are typically **absent or very mild** during recurrent episodes due to partial immunity. *Duration of symptoms* - While primary HSV infections often have a **longer duration of symptoms** compared to recurrent outbreaks, this is not the most definitive differentiating factor as there can be overlap [1]. - Recurrent lesions tend to resolve more quickly due to the host's existing immune response [1]. *Number of lesions* - Primary infections generally present with a **greater number and wider distribution of lesions** compared to recurrent episodes [3]. - However, the size and extent of an outbreak can vary, making it less specific than systemic symptoms for differentiation. *Location of lesions* - The location of lesions is often **consistent in recurrent HSV infections**, usually appearing in the same or adjacent anatomical region as the primary infection [2]. - While primary infections might have a broader initial distribution, this isn't the primary differentiating factor compared to the presence of systemic symptoms. *Viral culture positivity* - **Viral cultures are typically positive for both primary and recurrent HSV infections**, indicating active viral shedding [3]. - Therefore, culture positivity does not help differentiate between a primary and a recurrent episode.

Q: A 24-year-old woman presents with painful genital ulcers and lymphadenopathy. Tzanck smear shows multinucleated giant cells. What is the most appropriate initial treatment?

Valacyclovir 1g BD for 7-10 days. ***Valacyclovir 1g BD for 7-10 days*** - This is the **preferred initial treatment** for first-episode genital herpes due to its **superior bioavailability** (55% vs 15-20% for acyclovir) and convenient twice-daily dosing. - The **multinucleated giant cells** on Tzanck smear confirm **HSV infection**, and valacyclovir provides excellent therapeutic efficacy with improved **patient adherence**. *Acyclovir 400mg TID for 7-10 days* - This is a **valid CDC-recommended regimen** for first-episode genital herpes, not just for suppressive therapy or recurrent episodes. - However, it requires **three-times-daily dosing** which may reduce patient compliance compared to valacyclovir's twice-daily schedule. *Famciclovir 250mg TID for 7-10 days* - This is the **correct CDC-recommended dose** for first-episode genital herpes treatment (250mg TID for 7-10 days). - While effective as a **prodrug of penciclovir**, valacyclovir is generally preferred due to its more convenient dosing schedule and established efficacy profile. *Acyclovir 200mg 5 times daily for 7-10 days* - This is another **valid CDC-recommended regimen** for initial genital herpes episodes with proven clinical efficacy. - The **five-times-daily dosing** is less convenient and may lead to **poor adherence** compared to valacyclovir's twice-daily regimen.

Q: Pleomorphic rash is a feature of:

Chickenpox. ***Chickenpox*** - A **pleomorphic rash** in chickenpox means that lesions in different stages of development (macules, papules, vesicles, scabs) are present simultaneously in the same body area. - This characteristic presentation is a key diagnostic feature, differentiating it from smallpox where lesions typically appear in synchronized stages. *Smallpox* - The rash in smallpox tends to be **monomorphic**, meaning all lesions in a given area are at the same stage of development. - Smallpox lesions are typically *deep-seated*, firm, and progress slowly over several days. *Erythema subitum* - Also known as **roseola infantum**, this condition typically presents with a high fever followed by a **maculopapular rash** that appears as the fever breaks. - The rash is not pleomorphic and usually consists of small, discrete, rose-pink spots. *Erythema infectiosum* - Also known as **fifth disease**, it is characterized by a "slapped cheek" rash on the face, followed by a **lacelike or reticular rash** on the trunk and extremities. - The rash is not pleomorphic; its appearance is distinct and usually fades and reappears over several weeks.

Q: A child presents with grouped vesicles on the lips. What is the bedside investigation that you would like to do?

Tzanck smear. ***Tzanck smear*** - A **Tzanck smear** is a rapid bedside test that can identify **multinucleated giant cells**, which are seen in herpes simplex virus infections. - The presence of **grouped vesicles on the lips** is highly suggestive of **herpes labialis** (HSV-1), which is primarily a **clinical diagnosis**. - Among the options provided, Tzanck smear is the only relevant bedside investigation, though it has **limited sensitivity and specificity** and **cannot distinguish between HSV and VZV**. - In modern practice, **PCR or direct immunofluorescence** are preferred when laboratory confirmation is needed, but Tzanck smear remains a low-cost option in resource-limited settings. *Wood's lamp* - A Wood's lamp uses **ultraviolet light** to detect certain fungal or bacterial infections by revealing characteristic fluorescence. - It is useful for conditions like **tinea capitis** (green fluorescence) and **erythrasma** (coral-red fluorescence), but has no role in diagnosing viral vesicular lesions. *Slit skin smear* - A **slit skin smear** is used to detect **acid-fast bacilli** in the diagnosis of **leprosy**. - It is not indicated for vesicular lesions and is irrelevant to herpes simplex infection. *KOH* - A **KOH (potassium hydroxide) mount** is used to diagnose **fungal infections** by dissolving keratinocytes and revealing fungal hyphae or spores. - It has no utility in diagnosing viral infections such as herpes simplex.

Q: Which of the following is true about secondary herpes simplex?

All of the options. **All of the options** - **Secondary herpes simplex**, also known as recurrent herpes, often presents with visible symptoms like **painful ulcers**, typically on the **lips, hard palate, and gingiva** [1]. - **Acyclovir** is a primary antiviral treatment used to manage and reduce the severity and duration of secondary herpes simplex outbreaks. *Treatment – Acyclovir* - While acyclovir is indeed a standard treatment for herpes simplex, this option alone does not encompass all accurate statements regarding secondary herpes. - Acyclovir works by inhibiting viral DNA synthesis, helping to alleviate symptoms and prevent further viral replication. *Symptoms- Painful ulcers* - **Painful ulcers** are a characteristic symptom of secondary herpes simplex, particularly during outbreaks [2]. - These lesions are crucial for clinical diagnosis and patient discomfort. *Location – Lips, Hard palate and gingival* - The **lips (herpes labialis)**, **hard palate**, and **gingiva (herpetic gingivostomatitis)** are common sites for recurrent herpes simplex virus (HSV) infections due to viral latency in associated neural ganglia [1]. - Localization is a key diagnostic feature distinguishing it from other oral lesions.

Q: Pseudo koebner's sign is seen in

Warts. ***Warts*** - The **pseudo-Koebner phenomenon** refers to the appearance of new lesions at sites of trauma due to **viral inoculation** rather than an isomorphic response of a pre-existing dermatosis. - **Warts** (verruca vulgaris) caused by **human papillomavirus (HPV)** classically demonstrate pseudo-Koebner phenomenon, where the virus is inoculated into traumatized or abraded skin, leading to new wart formation along the trauma line. - Similarly, **molluscum contagiosum** can also show pseudo-Koebner phenomenon through viral seeding at trauma sites. *Psoriasis* - Psoriasis exhibits the **true Koebner phenomenon** (isomorphic response), not pseudo-Koebner. - In true Koebner, pre-existing psoriatic disease manifests as new psoriatic lesions at sites of trauma due to immune-mediated mechanisms. - This is fundamentally different from viral inoculation seen in pseudo-Koebner. *Lichen planus* - Lichen planus also demonstrates **true Koebner phenomenon**, where new lichen planus lesions appear at trauma sites. - This represents an isomorphic immune response, not viral spread, and therefore is not pseudo-Koebner phenomenon. *Inverse psoriasis* - Inverse psoriasis affects **intertriginous areas** (skin folds) and does not typically manifest Koebner or pseudo-Koebner phenomena. - The smooth, erythematous patches in flexural areas are less prone to the superficial trauma needed to elicit these responses.

Q: What is the diagnosis of an umbilicated, pearly white, asymptomatic skin lesion?

Molluscum contagiosum. ***Molluscum contagiosum*** - This **viral skin infection** typically presents with **multiple, small (2-5 mm), firm, pearly, dome-shaped papules** that have a **central umbilication**. - The lesions are usually **asymptomatic**, as described, though they can occasionally be itchy or inflamed. - Caused by a **poxvirus** and is highly contagious through direct contact. *EBV* - **Epstein-Barr Virus (EBV)** is primarily associated with **infectious mononucleosis**, which presents with fever, sore throat, and lymphadenopathy, not umbilicated skin lesions. - EBV can cause oral hairy leukoplakia in immunocompromised individuals, which is a white lesion, but it is **not pearly, umbilicated, or dome-shaped**. *HSV* - **Herpes Simplex Virus (HSV)** causes lesions that are typically **grouped vesicles on an erythematous base** that evolve into erosions or ulcers. - HSV lesions are often **painful or itchy** and **do not appear as pearly, umbilicated papules**. *None of the options* - This is incorrect because **Molluscum contagiosum** perfectly matches the clinical description of umbilicated, pearly white, asymptomatic skin lesions. - The classic **central umbilication** is the pathognomonic feature that distinguishes molluscum from other viral skin infections.

Q: Which of the following types of wart is treated by local application of podophyllin?

Genital wart. ***Genital wart*** - **Podophyllin** is an antimitotic agent that is commonly used for the topical treatment of **genital warts (condyloma acuminata)**. - Its mechanism involves arresting cell division in metaphase, leading to **necrosis of the wart tissue**. *All of the options* - While podophyllin is effective for some warts, it is not universally recommended for all types due to potential side effects and varying efficacy. - Other wart types, such as **plantar warts** and **verruca vulgaris**, often require different treatment modalities like salicylic acid, cryotherapy, or surgical excision. *Plantar wart* - **Plantar warts** are typically located on the soles of the feet and are often treated with **salicylic acid**, cryotherapy, or laser therapy, as they can be resistant to topical podophyllin. - The thick stratum corneum on the soles of the feet can limit the penetration of podophyllin, making it less effective for these warts. *Verruca wart* - The term "**verruca wart**" is general and usually refers to **verruca vulgaris** (common warts), which are often found on hands and fingers. - Treatment for common warts typically includes **cryotherapy**, salicylic acid preparations, or duct tape occlusion, rather than podophyllin, which can cause significant irritation on non-genital skin.

Question 1

A young man presented with painful vesicular lesions distributed along a dermatomal pattern on one side of his body. What is the likely diagnosis?

Accepted Answer

Herpes Zoster

Answer

Lymphangioma circumscriptum

Answer

Molluscum contagiosum

Answer

Herpes simplex

Question 2

A 25-year-old woman presents for STI screening. She reports consistent condom use with her partner. Which of the following STIs is least effectively prevented by proper condom use?

Accepted Answer

HPV

Answer

Chlamydia

Answer

Gonorrhea

Answer

HIV

Answer

Hepatitis B

Question 3

A 35-year-old man presents with burning penile lesions 3 days after unprotected intercourse. He has no prior history of similar lesions. Which of the following best differentiates primary from recurrent HSV infection?

Accepted Answer

Systemic symptoms and bilateral lymphadenopathy

Answer

Duration of symptoms

Answer

Number of lesions

Answer

Location of lesions

Answer

Viral culture positivity

Question 4

A 24-year-old woman presents with painful genital ulcers and lymphadenopathy. Tzanck smear shows multinucleated giant cells. What is the most appropriate initial treatment?

Accepted Answer

Valacyclovir 1g BD for 7-10 days

Answer

Acyclovir 400mg TID for 7-10 days

Answer

Acyclovir 200mg 5 times daily for 7-10 days

Answer

Famciclovir 250mg TID for 7-10 days

Question 5

Pleomorphic rash is a feature of:

Accepted Answer

Chickenpox

Answer

Smallpox

Answer

Erythema subitum

Answer

Erythema infectiosum

Question 6

A child presents with grouped vesicles on the lips. What is the bedside investigation that you would like to do?

Accepted Answer

Tzanck smear

Answer

Wood's lamp

Answer

Slit skin smear

Answer

KOH

Question 7

Which of the following is true about secondary herpes simplex?

Accepted Answer

All of the options

Answer

Treatment – Acyclovir

Answer

Symptoms- Painful ulcers

Answer

Location – Lips, Hard palate and gingival

Question 8

Pseudo koebner's sign is seen in

Accepted Answer

Warts

Answer

Inverse psoriasis

Answer

Psoriasis

Answer

Lichen planus

Question 9

What is the diagnosis of an umbilicated, pearly white, asymptomatic skin lesion?

Accepted Answer

Molluscum contagiosum

Answer

EBV

Answer

HSV

Answer

None of the options

Question 10

Which of the following types of wart is treated by local application of podophyllin?

Accepted Answer

Genital wart

Answer

All of the options

Answer

Plantar wart

Answer

Verruca wart

Viral Skin Infections — MCQs

Viral Skin Infections — MCQs

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