Viral Exanthems — MCQs
A child presented with bluish-white spots in the mouth followed by a rash. What is the genome of the most likely causative agent?
Koplik's spots occur in which phase of measles -
Which of the following characteristics can be used to differentiate the rash of chickenpox from the rash of smallpox?
True about measles
A 25-year-old male presents with a cluster of vesicles along the dermatome on his chest and back. He complains of burning pain in the same area. What is the most likely diagnosis?
Which of the following statements about Pityriasis rosea is true?
In which condition are Bull's eye lesions typically found?
A woman presents with lesions on the inner thighs and peri-anal region. They are nodular, 4-6 mm in size and appear pale. The histopathological image shows multiple intracytoplasmic inclusion bodies consistent with Henderson-Patterson bodies. The diagnosis is:
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?
A child presents with grouped vesicles on the lips. What is the bedside investigation that you would like to do?
Viral Exanthems Indian Medical PG Practice Questions and MCQs
Question 1: A child presented with bluish-white spots in the mouth followed by a rash. What is the genome of the most likely causative agent?
- A. Enveloped virus with single-stranded RNA (Correct Answer)
- B. Double stranded Naked RNA
- C. Naked virus with single-stranded RNA
- D. Double stranded Enveloped RNA
Explanation: ***Enveloped virus with single-stranded RNA*** - Bluish-white spots in the mouth (**Koplik spots**) followed by a rash are pathognomonic for **measles**, which is caused by the **measles virus**. - The measles virus is a **paramyxovirus**, characterized as an **enveloped, negative-sense, single-stranded RNA virus**. *Double stranded Naked RNA* - No major human pathogen belongs to this specific genomic and structural classification. - Most **dsRNA viruses** like **rotavirus** are **naked** but cause gastroenteritis, not measles. *Naked virus with single-stranded RNA* - Viruses like **rhinovirus** (common cold) or **poliovirus** fit this description but do not cause Koplik spots or measles. - **Naked viruses** lack a lipid envelope, making them generally more resistant to environmental factors. *Double stranded Enveloped RNA* - There are no known medically significant human viruses that are both **enveloped** and contain **double-stranded RNA**. - Viral genomes are typically either DNA or RNA, and RNA viruses are usually single-stranded (positive or negative sense) or double-stranded, with or without an envelope.
Question 2: Koplik's spots occur in which phase of measles -
- A. Post exanthematous phase
- B. End of prodromal phase (Correct Answer)
- C. Recrudescence phase
- D. Exanthematous phase
Explanation: ***End of prodromal phase*** - **Koplik's spots**, pathognomonic for measles, typically appear 1-2 days before the onset of the **maculopapular rash**, marking the very end of the **prodromal phase**. - These are small, white spots with a bluish-white center on an erythematous base, found on the **buccal mucosa** opposite the molars. *Post exanthematous phase* - This phase occurs *after* the rash has faded and is characterized by **desquamation** and **cough**, not the appearance of Koplik's spots. - Koplik's spots would have long disappeared by this stage. *Recrudescence phase* - This term usually refers to the **reappearance of symptoms** after a period of improvement, which is not characteristic of Koplik's spots in measles. - Koplik's spots represent an initial diagnostic sign rather than a recurrent symptom. *Exanthematous phase* - The **exanthematous phase** is when the characteristic **maculopapular rash** appears and spreads, typically starting a few days *after* Koplik's spots have already emerged and are beginning to fade. - While overlap can occur, Koplik's spots are *most prominent* and diagnostic *before* the rash fully develops.
Question 3: Which of the following characteristics can be used to differentiate the rash of chickenpox from the rash of smallpox?
- A. Deep-seated
- B. Pleomorphic (Correct Answer)
- C. Centrifugal
- D. Multilocular
Explanation: ***Pleomorphic*** - The rash of **chickenpox** is **pleomorphic**, meaning lesions at various stages of development (macules, papules, vesicles, scabs) are present simultaneously in the same body area. - In contrast, a **smallpox** rash is **monomorphic**, with all lesions in a given area appearing at the same stage of development. *Centrifugal* - A **centrifugal distribution** (lesions more concentrated on the face and extremities) is characteristic of **smallpox**. - **Chickenpox** typically has a **centripetal distribution**, with lesions more concentrated on the trunk. *Deep-seated* - **Smallpox** lesions are described as **deep-seated** and feel like "shot under the skin," often associated with significant scarring. - **Chickenpox** lesions are superficial and less likely to cause scarring unless secondarily infected. *Multilocular* - **Smallpox** vesicles and pustules are typically **multilocular**, meaning they have internal septations and do not collapse when punctured. - **Chickenpox** vesicles are unilocular, appearing as a single compartment, and collapse when punctured.
Question 4: True about measles
- A. Long term complication follows in form of SSPE (Correct Answer)
- B. Rash appear first on leg
- C. Koplik spots are seen in retina
- D. Caused by DNA virus
Explanation: ***Long term complication follows in form of SSPE*** - **Subacute sclerosing panencephalitis (SSPE)** is a rare, but fatal, progressive neurodegenerative disease that can develop years after a measles infection [1]. - It is caused by persistent measles virus in the brain, leading to **neurological deterioration** and eventually death [2]. *Rash appear first on leg* - The characteristic rash of measles typically appears first on the **face and behind the ears**, then spreads downward to the trunk and extremities [1]. - The rash is usually **maculopapular** and confluent, turning brownish and fading in the same order it appeared [1]. *Koplik spots are seen in retina* - **Koplik spots** are pathognomonic for measles and are found on the **buccal mucosa** (inside the cheeks), opposite the molars [1]. - They appear as small, white, or bluish-white spots with an erythematous base before the onset of the rash. *Caused by DNA virus* - Measles is caused by the **measles virus**, which is a **single-stranded RNA virus** belonging to the genus *Morbillivirus* in the family *Paramyxoviridae*. - It is not a DNA virus; this classification has significant implications for its replication cycle and vaccine development.
Question 5: A 25-year-old male presents with a cluster of vesicles along the dermatome on his chest and back. He complains of burning pain in the same area. What is the most likely diagnosis?
- A. Herpes zoster (Correct Answer)
- B. Contact dermatitis
- C. Herpes simplex
- D. Impetigo
Explanation: ***Herpes zoster*** - The classic presentation of **vesicular rash along a dermatome** with **burning pain** is highly characteristic of herpes zoster (shingles). - This condition is caused by the **reactivation of the varicella-zoster virus (VZV)**, which lies dormant in sensory ganglia. *Contact dermatitis* - This condition typically presents as an **itchy, erythematous rash** that appears after contact with an allergen or irritant. - While vesicles can be present, the rash is usually not strictly confined to a single dermatome and **burning pain is less common** than itching. *Herpes simplex* - Herpes simplex virus (HSV) typically causes **localized clusters of vesicles** on mucosal surfaces (e.g., oral, genital) or skin. - It does not usually present with a **dermatomal distribution** on the trunk as described in the vignette. *Impetigo* - Impetigo is a **bacterial skin infection** characterized by **honey-crusted lesions** or pustules. - While it can involve vesicles, it does not follow a **dermatomal pattern** and is caused by bacteria, not a viral reactivation.
Question 6: Which of the following statements about Pityriasis rosea is true?
- A. It is a self-limiting condition. (Correct Answer)
- B. It can lead to life-threatening infections.
- C. It is caused by dermatophytes.
- D. It is a chronic relapsing condition.
Explanation: ***It is a self-limiting condition.*** - **Pityriasis rosea** is characterized by a distinctive rash that typically resolves on its own within **6-8 weeks** without specific treatment. - Most patients experience complete resolution, and **recurrences are uncommon**. - Often preceded by a **herald patch** followed by smaller oval lesions in a **"Christmas tree" distribution** on the trunk. *It can lead to life-threatening infections.* - While the exact etiology is unknown, **Pityriasis rosea** is generally considered **benign** and does not typically lead to systemic complications or life-threatening infections. - The rash itself is a localized skin condition that does not compromise the immune system or predispose to severe secondary infections. *It is caused by dermatophytes.* - **Dermatophytes** are fungi that cause superficial fungal infections such as ringworm (**tinea** infections). - **Pityriasis rosea** is thought to be triggered by certain **viral infections**, particularly **human herpesvirus 6 (HHV-6)** and **HHV-7**, not fungal organisms. - This helps differentiate it from fungal conditions like tinea corporis. *It is a chronic relapsing condition.* - **Pityriasis rosea** is generally an **acute, self-limiting eruption** that resolves spontaneously, making it distinct from chronic, relapsing conditions such as **psoriasis** or **eczema**. - A single episode usually confers long-lasting immunity, and **recurrences are rare** (occurring in <2% of cases).
Question 7: In which condition are Bull's eye lesions typically found?
- A. Erythema nodosum
- B. Erythema gangrenosum
- C. Erythema multiforme (Correct Answer)
- D. Erythroderma
Explanation: ***Erythema multiforme*** - **Bull's eye lesions**, also known as **target lesions**, are the hallmark clinical finding in erythema multiforme. - These lesions feature a central dusky or blistered area, surrounded by a pale edematous ring, and an outermost erythematous halo. *Erythema nodosum* - Characterized by tender, red, subcutaneous nodules, typically located on the **shins**. - It represents a form of **panniculitis** (inflammation of subcutaneous fat) and does not exhibit targetoid morphology. *Erythema gangrenosum* - A specific skin lesion associated with **Pseudomonas aeruginosa** septicemia, characterized by hemorrhagic bullae that progress to necrotic ulcers with a black eschar. - It represents **necrotizing vasculitis** and does not present with bull's eye or target lesions. *Erythroderma* - Defined as generalized redness and scaling affecting more than **90% of the body surface area**. - This condition involves widespread inflammation of the skin and does not present with discrete target lesions.
Question 8: A woman presents with lesions on the inner thighs and peri-anal region. They are nodular, 4-6 mm in size and appear pale. The histopathological image shows multiple intracytoplasmic inclusion bodies consistent with Henderson-Patterson bodies. The diagnosis is:
- A. Trichodysplasia spinulosa
- B. Molluscum contagiosum (Correct Answer)
- C. Condyloma acuminata
- D. Donovanosis
Explanation: ***Molluscum contagiosum*** - The clinical presentation of **nodular, pale lesions** in the inner thighs and peri-anal region, combined with histopathology showing **Henderson-Patterson bodies** (large eosinophilic intracytoplasmic inclusions), is pathognomonic for molluscum contagiosum. - Henderson-Patterson bodies represent viral factories within infected keratinocytes, a key diagnostic feature of this **poxvirus** infection. *Trichodysplasia spinulosa* - This condition is characterized by **follicular papules** with prominent keratin spines, typically occurring on the face, and is associated with the **Trichodysplasia spinulosa-associated polyomavirus**. - It does not present with Henderson-Patterson bodies or the typical nodular lesions seen in molluscum contagiosum. *Condyloma acuminata* - These are **genital warts** caused by the **human papillomavirus (HPV)**, presenting as verrucous or cauliflower-like growths. - Histologically, they show **koilocytic atypia** (vacuolated cells with nuclear abnormalities), not Henderson-Patterson bodies. *Donovanosis* - Also known as **granuloma inguinale**, this is a chronic, progressive, ulcerative granulomatous disease caused by **Klebsiella granulomatis**. - Histopathology reveals **Donovan bodies** (intracellular bacteria within macrophages), which are distinct from Henderson-Patterson bodies and the clinical presentation of nodular lesions.
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?
- A. Adenovirus
- B. HPV (Correct Answer)
- C. Molluscum contagiosum virus
- D. Echovirus
Explanation: ***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.
Question 10: A child presents with grouped vesicles on the lips. What is the bedside investigation that you would like to do?
- A. Wood's lamp
- B. Slit skin smear
- C. Tzanck smear (Correct Answer)
- D. KOH
Explanation: ***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.
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