Viral Skin Infections Practice Questions

Q: An individual develops a high-grade fever lasting for 3 days, after which a vesicular rash appears. The rash is predominantly centripetal, involving the trunk more than the extremities, as shown in the image. What is the most likely diagnosis?

Chickenpox (Varicella). ***Chickenpox (Varicella)*** - The classic presentation involves a prodromal **fever** followed by a **centripetal distribution** of rash, where lesions are most concentrated on the **trunk** rather than the extremities. - The rash typically appears in **crops** and progresses through stages of **macules, papules, vesicles, and crusts** simultaneously (pleomorphism). *Dengue* - Characterized by a **biphasic fever** (

Q: A young woman presents with vesiculobullous lesions involving the upper lips and target lesions on extremities. What is the most likely diagnosis?

Erythema multiforme. ***Erythema multiforme*** - Classically presents with **target lesions** (iris lesions) on the extremities and **mucosal involvement** (like lips/oral cavity) with vesiculobullous eruptions. - It is a **type IV hypersensitivity reaction**, most commonly triggered by **Herpes Simplex Virus (HSV)** infection, especially in recurrent cases. *Dermatitis herpetiformis* - Characterized by **pruritic vesicles** symmetrically distributed on extensor surfaces, elbows, and buttocks. - It is strongly associated with **celiac disease** (gluten-sensitive enteropathy), not target lesions. *Bullous pemphigoid* - Typically occurs in the **elderly** as tense, **subepidermal bullae** on flexural surfaces. - Mucosal involvement is much less common and less severe compared to pemphigus vulgaris or EM. *Pemphigus vulgaris* - Manifests as **flaccid bullae** and mucosal **ulcerations** that rupture easily due to autoantibodies against **desmoglein 3**. - It shows a **positive Nikolsky sign** and acantholysis on histology, unlike the target lesions seen in EM.

Q: A male patient reports painful vesicular eruptions on the penis. Based on this presentation, which of the following is the most likely causative agent?

Herpes simplex virus. ***Herpes simplex virus*** - Infection with **Herpes simplex virus (HSV-2)** typically manifests as clusters of **painful vesicles** that rupture to form shallow, erythematous ulcers on the genitalia. - The clinical presentation is classic for primary genital herpes, which is often accompanied by **inguinal lymphadenopathy** and systemic symptoms like fever or malaise. *Haemophilus ducreyi* - This bacterium causes **chancroid**, which presents as a painful, deep, necrotic, and **purulent ulcer** rather than clusters of vesicles. - The base of the ulcer typically has gray/yellow exudate and bleeds easily, unlike the clear vesicular lesions of HSV. *Human papillomavirus* - This virus causes **condyloma acuminatum** (genital warts), which appear as **fleshy, cauliflower-like growths** rather than vesicular eruptions. - These lesions are usually asymptomatic or pruritic and are not typically associated with painful vesicle formation or acute rupture. *Treponema pallidum* - This organism causes **syphilis**, where the primary stage presents as a **chancre**, which is a **painless, indurated ulcer** with a clean base. - Unlike the painful vesicles of HSV, the primary syphilitic lesion is classically described as non-tender and associated with **regional lymphadenopathy**.

Q: What is the most likely diagnosis for this 19-month-old girl who presented with a 1-week history of an ascending erythematous eruption?

Herpes zoster. **Explanation:** The correct diagnosis is **Herpes Zoster (Shingles)**. While commonly associated with the elderly, Herpes Zoster can occur in children, especially those who were infected with Varicella Zoster Virus (VZV) in utero or during the first year of life. The "ascending erythematous eruption" in this clinical scenario refers to a **dermatomal distribution**. Herpes Zoster is caused by the reactivation of latent VZV from the dorsal root ganglia. In pediatric patients, the presentation is often milder than in adults, frequently lacking the classic prodromal pain or post-herpetic neuralgia, which can make the diagnosis challenging if the clinician only expects "adult-type" symptoms. **Why the other options are incorrect:** * **Cellulitis:** This typically presents as a spreading, poorly demarcated area of skin erythema, warmth, and edema. It does not follow a dermatomal pattern and is usually associated with systemic signs like high fever. * **Hand, Foot, and Mouth Disease (HFMD):** Caused by Coxsackievirus A16, this presents with vesicular lesions on the palms, soles, and oral mucosa. It is not dermatomal or "ascending" in a linear nerve distribution. * **Lymphadenitis:** This refers to the inflammation/infection of lymph nodes. While it may cause localized swelling and redness, it does not present as a vesicular or erythematous eruption following a nerve path. **NEET-PG High-Yield Pearls:** * **Risk Factor:** The single greatest risk factor for pediatric Herpes Zoster is **primary varicella infection before age 1**. * **Distribution:** The most common sites in children are the **thoracic** and **lumbar** dermatomes. * **Diagnosis:** Usually clinical; however, the **Tzanck smear** (showing multinucleated giant cells) or PCR are definitive. * **Management:** In healthy children, the condition is often self-limiting; acyclovir is reserved for immunocompromised patients or severe cases.

Q: What topical immunomodulator is used for the treatment of genital warts?

Imiquimod. **Explanation:** **Correct Answer: A. Imiquimod** Imiquimod is a potent **topical immunomodulator** used for the treatment of external genital and perianal warts (Condyloma acuminata) caused by Human Papillomavirus (HPV). Its mechanism of action involves binding to **Toll-like receptor 7 (TLR-7)** on antigen-presenting cells. This stimulates the release of pro-inflammatory cytokines, primarily **Interferon-alpha (IFN-α)**, Interleukin-6, and TNF-alpha, which enhance the body's cell-mediated immune response to eliminate the virus-infected cells. **Analysis of Incorrect Options:** * **B. Podophyllin:** This is a **cytotoxic/antimitotic agent**, not an immunomodulator. It works by arresting mitosis in metaphase, leading to tissue necrosis. It is contraindicated in pregnancy. * **C. Interferon:** While interferons have immunomodulatory properties and can be used intralesionally for warts, they are not the primary *topical* immunomodulator of choice in standard clinical practice compared to Imiquimod. * **D. Acyclovir:** This is an **antiviral** drug that inhibits DNA polymerase. It is used for Herpes Simplex Virus (HSV) and Varicella-Zoster Virus (VZV), but it has no efficacy against HPV (warts). **High-Yield Clinical Pearls for NEET-PG:** * **Imiquimod Strengths:** Available as 5% (standard) and 3.75% creams. * **Other Indications:** Also used for Actinic Keratosis and superficial Basal Cell Carcinoma (BCC). * **HPV Strains:** Genital warts are most commonly caused by **HPV types 6 and 11** (low-risk types). * **Podophyllotoxin:** Unlike Podophyllin resin, Podophyllotoxin is a purified extract that can be self-applied by the patient.

Q: Podophyllin resin is indicated for the treatment of?

Anogenital warts. **Explanation:** **Podophyllin resin** is a topical cytotoxic agent derived from the roots of the *Podophyllum* plant. It acts as an **antimitotic agent** by binding to tubulin and preventing microtubule assembly, which leads to cell cycle arrest in metaphase. This mechanism makes it effective in treating **Anogenital warts (Condyloma acuminata)**, which are caused by Human Papillomavirus (HPV) types 6 and 11. **Analysis of Options:** * **Anogenital warts (Correct):** Podophyllin is a classic chemical cauterant used for external genital and perianal warts. It induces necrosis of the infected epithelial cells. * **Syphilis (Incorrect):** Caused by *Treponema pallidum*; the treatment of choice is **Penicillin G**. * **Herpes genitalis (Incorrect):** Caused by HSV-1 or HSV-2; treated with antiviral drugs like **Acyclovir, Valacyclovir, or Famciclovir**. * **Lymphogranuloma venereum (Incorrect):** Caused by *Chlamydia trachomatis* (L1-L3); the treatment of choice is **Doxycycline**. **High-Yield Clinical Pearls for NEET-PG:** * **Contraindication:** Podophyllin is strictly **contraindicated in pregnancy** due to its potential for systemic absorption and teratogenicity (fetal death/limb malformations). * **Application:** It must be washed off within 4–6 hours to prevent severe local irritation and systemic toxicity (neurotoxicity, bone marrow suppression). * **Podophyllotoxin:** This is the purified active ingredient of podophyllin. It is more stable, less toxic, and can be self-applied by the patient, unlike the resin which must be applied by a physician. * **Other treatments for Warts:** Imiquimod (immunomodulator), Cryotherapy (Liquid Nitrogen), and Trichloroacetic acid (TCA).

Q: A 56-year-old man presents with painful rashes over his right upper eyelid and forehead for the last 48 hours. He underwent chemotherapy for Non-Hodgkin's lymphoma one year ago. His vital signs are stable. Physical examination reveals no other abnormalities. What is the most likely diagnosis?

Herpes zoster. ### Explanation **Correct Answer: B. Herpes zoster** **Clinical Reasoning:** The presentation of painful, unilateral rashes localized to a specific dermatome (in this case, the **ophthalmic division of the Trigeminal nerve - V1**) is classic for **Herpes Zoster (Shingles)** [1]. The patient’s history of chemotherapy for Non-Hodgkin’s lymphoma indicates an immunocompromised state, which is a major risk factor for the reactivation of the latent Varicella-Zoster Virus (VZV) from the sensory ganglia [1]. When V1 is involved, it is termed *Herpes Zoster Ophthalmicus*. **Analysis of Incorrect Options:** * **A. Impetigo:** Usually presents as honey-colored crusting, typically in children. It is not dermatomal and is generally painless or mildly pruritic rather than severely painful. * **C. Pyoderma gangrenosum:** An inflammatory neutrophilic dermatosis presenting as rapidly enlarging, painful ulcers with undermined violaceous edges, often associated with IBD or RA, not a dermatomal vesicular rash. * **D. Erysipelas:** A superficial bacterial cellulitis (usually Group A Strep) characterized by a well-demarcated, raised, bright red "orange-peel" (peau d'orange) lesion [2]. While it can affect the face, it lacks the dermatomal distribution and vesicular nature of Zoster. **High-Yield NEET-PG Pearls:** * **Hutchinson’s Sign:** Vesicles on the tip or side of the nose indicate involvement of the nasociliary nerve (branch of V1) and predict a high risk of ocular complications (e.g., keratitis). * **Treatment:** Oral Acyclovir, Valacyclovir, or Famciclovir should ideally be started within **72 hours** of rash onset [1]. * **Complication:** The most common chronic complication is **Post-herpetic neuralgia (PHN)**, defined as pain persisting >90 days after the rash heals [1]. * **Ramsay Hunt Syndrome:** Reactivation in the geniculate ganglion involving CN VII and VIII (triad of facial palsy, ear pain, and vesicles in the auditory canal).

Q: Flat wart is caused by which HPV types?

3, 10. **Explanation:** **Flat warts (Verruca plana)** are benign epithelial proliferations caused by the **Human Papillomavirus (HPV)**. The correct answer is **Option B (3, 10)** because these specific genotypes have a high tropism for the superficial dermis, leading to the characteristic smooth, flat-topped, flesh-colored to brownish papules typically seen on the face, neck, and dorsum of the hands. **Analysis of Options:** * **A (6, 11):** These are the "low-risk" types primarily responsible for **Anogenital warts (Condyloma acuminata)** and laryngeal papillomas. * **C (16, 18):** These are "high-risk" oncogenic types. They are the leading cause of **Cervical Cancer**, as well as other anogenital and oropharyngeal malignancies. * **D (5, 8):** These types are associated with **Epidermodysplasia Verruciformis (EV)**. In these patients, HPV 5 and 8 carry a high risk of progressing to Squamous Cell Carcinoma (SCC) in sun-exposed areas. **High-Yield Clinical Pearls for NEET-PG:** 1. **Koebner Phenomenon:** Flat warts frequently exhibit linear distribution due to autoinoculation following scratching or trauma. 2. **Histopathology:** Look for "Koilocytes" (keratinocytes with pyknotic nuclei and perinuclear halos) in the upper epidermis. 3. **Common Wart (Verruca Vulgaris):** Most commonly caused by **HPV types 1, 2, and 4**. 4. **Palmar/Plantar Warts (Myrmecia):** Primarily caused by **HPV type 1**. 5. **Butcher’s Warts:** Associated with **HPV type 7**.

Q: Slapped-cheek appearance is seen in which of the following viral infections?

Parvovirus B19. **Explanation:** **Parvovirus B19 (Correct Answer):** The "slapped-cheek" appearance is the pathognomonic clinical feature of **Erythema Infectiosum**, also known as **Fifth Disease**, caused by Parvovirus B19. The rash typically presents in three stages: 1. **Stage 1:** Erythematous, edematous plaques on the cheeks (slapped-cheek) with perioral sparing. 2. **Stage 2:** A reticulate or "lace-like" erythematous maculopapular rash on the trunk and extremities. 3. **Stage 3:** Recurrence of the rash triggered by sunlight, heat, or stress. **Incorrect Options:** * **Epstein-Barr Virus (EBV) / HHV-4:** EBV causes Infectious Mononucleosis. While it can cause a non-specific rash, it is classically associated with a **maculopapular drug eruption** following the administration of Ampicillin or Amoxicillin. * **Human Herpesvirus 6 (HHV-6):** This is the causative agent of **Roseola Infantum (Exanthem Subitum)**. It is characterized by high fever that subsides abruptly, followed by the appearance of a rose-pink morbilliform rash (fever ends before the rash begins). **Clinical Pearls for NEET-PG:** * **Target Cells:** Parvovirus B19 infects and lyses **erythroid progenitor cells** (P-antigen is the receptor). * **Hematologic Complication:** It can cause **Aplastic Crisis** in patients with chronic hemolytic anemias (e.g., Sickle Cell Anemia, Hereditary Spherocytosis). * **Pregnancy:** Infection during pregnancy can lead to **Hydrops Fetalis** due to severe fetal anemia. * **Adults:** In adults, it often presents as **symmetrical arthralgia** (small joints of hands/feet) rather than the classic rash. * **Gloves and Socks Syndrome:** A variant presentation characterized by painful erythema and edema of the hands and feet.

Question 1

An individual develops a high-grade fever lasting for 3 days, after which a vesicular rash appears. The rash is predominantly centripetal, involving the trunk more than the extremities, as shown in the image. What is the most likely diagnosis?

Accepted Answer

Chickenpox (Varicella)

Answer

Dengue

Answer

Smallpox

Answer

Measles

Question 2

A young woman presents with vesiculobullous lesions involving the upper lips and target lesions on extremities. What is the most likely diagnosis?

Accepted Answer

Erythema multiforme

Answer

Dermatitis herpetiformis

Answer

Bullous pemphigoid

Answer

Pemphigus vulgaris

Question 3

A male patient reports painful vesicular eruptions on the penis. Based on this presentation,
which of the following is the most likely causative agent?

Accepted Answer

Herpes simplex virus

Answer

Haemophilus ducreyi

Answer

Human papillomavirus

Answer

Treponema pallidum

Question 4

What is the most likely diagnosis for this 19-month-old girl who presented with a 1-week history of an ascending erythematous eruption?

Accepted Answer

Herpes zoster

Answer

Cellulitis

Answer

Hand, foot, and mouth disease

Answer

Lymphadenitis

Question 5

Which of the following is NOT true about molluscum contagiosum?

Accepted Answer

Molluscum bodies are seen intranuclearly with Giemsa staining.

Answer

Lesions are typically dome-shaped, umbilicated papules.

Answer

It is contagious until the lesions resolve.

Answer

Most lesions regress spontaneously within 6 to 12 months.

Question 6

What topical immunomodulator is used for the treatment of genital warts?

Accepted Answer

Imiquimod

Answer

Podophyllin

Answer

Interferon

Answer

Acyclovir

Question 7

Podophyllin resin is indicated for the treatment of?

Accepted Answer

Anogenital warts

Answer

Syphilis

Answer

Herpes genitalis

Answer

Lymphogranuloma venereum

Question 8

A 56-year-old man presents with painful rashes over his right upper eyelid and forehead for the last 48 hours. He underwent chemotherapy for Non-Hodgkin's lymphoma one year ago. His vital signs are stable. Physical examination reveals no other abnormalities. What is the most likely diagnosis?

Accepted Answer

Herpes zoster

Answer

Impetigo

Answer

Pyoderma gangrenosum

Answer

Erysipelas

Question 9

Flat wart is caused by which HPV types?

Accepted Answer

3, 10

Answer

6, 11

Answer

16, 18

Answer

5, 8

Question 10

Slapped-cheek appearance is seen in which of the following viral infections?

Accepted Answer

Parvovirus B19

Answer

Epstein-Barr Virus (EBV)

Answer

Human Herpesvirus 6 (HHV-6)

Answer

Human Herpesvirus 4 (HHV-4)

Viral Skin Infections — MCQs

Viral Skin Infections — MCQs

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