Impetigo — MCQs
Which organism is most associated with neonatal meningitis and skin rash?
Identify the diagnosis based on the dermatology immunofluorescence (IF) image provided.
An organism produces cutaneous disease (malignant pustule or eschar) at the site of inoculation in handlers of animal skins. Most likely organism is:
An 18-year-old man has facial and upper back lesions that have waxed and waned for the past 6 years. On physical examination, there are 0.3- to 0.9-cm comedones, erythematous papules, nodules, and pustules most numerous on the lower face and posterior upper trunk. Other family members have been affected by this condition at a similar age. The lesions worsen during a 5-day cruise to the Adriatic. Which of the following organisms is most likely to play a key role in the pathogenesis of these lesions?
What is the treatment for granuloma inguinale?
A 35-year-old obese woman presents with recurrent lesions in both axilla in summer season. Wood lamp examination is shown. The diagnosis is:
A young man presents with skin lesions as shown in the image below. All of the following organisms can spread through dermal and subcutaneous lymphatics, except
A child presents with grouped vesicles on an erythematous base on the buttocks. What is the most likely diagnosis?
A 22-year-old woman presents with multiple tender, erythematous nodules on her shins that developed over the past week. She reports having a sore throat 2 weeks ago. She also complains of joint pain and fatigue. Physical examination reveals raised, red, tender nodules on the anterior surface of both legs. Her temperature is 38.2°C. Which of the following is the most likely diagnosis?
The following image shows a flaccid bulla. This finding is characteristically seen in:
Impetigo Indian Medical PG Practice Questions and MCQs
Question 1: Which organism is most associated with neonatal meningitis and skin rash?
- A. VZV
- B. Group B Streptococcus (GBS)
- C. HSV-2 (Correct Answer)
- D. Enterovirus 71
Explanation: ***HSV-2*** - **Neonatal herpes simplex virus (HSV)** infection, often caused by HSV-2 acquired during vaginal delivery, can manifest with **meningitis** and characteristic **skin vesicles** or a rash. - The rash typically presents as clustered **vesicles on an erythematous base** and can be widespread, making it a key diagnostic clue alongside neurological symptoms. *VZV* - **Varicella-zoster virus (VZV)** can cause neonatal varicella, which presents with a rash but **meningitis** is a much less common complication, typically associated with more severe disseminated disease. - The rash of neonatal varicella usually appears as **macules, papules, vesicles, and scabs** in various stages of healing, rather than the clustered vesicles seen in HSV. *Group B Streptococcus (GBS)* - **GBS** is a leading cause of **neonatal meningitis** and sepsis, but it typically does **not cause a skin rash** in affected infants. - While GBS can cause systemic signs of infection and neurological symptoms, cutaneous manifestations are not characteristic. *Enterovirus 71* - **Enterovirus 71** is known to cause hand, foot, and mouth disease, which includes a **rash** and can, in severe cases, cause **meningitis** or encephalitis. - However, the rash is typically maculopapular or vesicular on the palms, soles, and buttocks, and this association is less common for neonatal meningitis with widespread skin findings compared to HSV.
Question 2: Identify the diagnosis based on the dermatology immunofluorescence (IF) image provided.
- A. Pemphigus vulgaris
- B. Pemphigus foliaceus
- C. Bullous pemphigoid
- D. Dermatitis herpetiformis (Correct Answer)
Explanation: ***Dermatitis herpetiformis*** - The immunofluorescence image shows **granular IgA deposits** at the **dermal papillae region**, which is characteristic of dermatitis herpetiformis. - This condition is strongly associated with **celiac disease** and presents with intensely pruritic papules and vesicles. *Pemphigus vulgaris* - Immunofluorescence in pemphigus vulgaris typically shows a **fishnet pattern** of IgG deposits throughout the **epidermis**, reflecting antibodies against desmoglein 3 and 1. - This pattern is an intercellular deposition, not granular at the dermal papillae. *Pemphigus foliaceus* - Similar to pemphigus vulgaris, pemphigus foliaceus also exhibits **intercellular IgG deposits** in the epidermis, but it is usually more superficial, targeting desmoglein 1. - The image does not show this intercellular epidermal staining. *Bullous pemphigoid* - Bullous pemphigoid is characterized by **linear IgG and C3 deposits along the dermal-epidermal junction** (basement membrane zone). - The image distinctly shows granular IgA, not linear IgG/C3, and specifically in the dermal papillae.
Question 3: An organism produces cutaneous disease (malignant pustule or eschar) at the site of inoculation in handlers of animal skins. Most likely organism is:
- A. Neisseria meningitidis
- B. Bacillus anthracis (Correct Answer)
- C. Pseudomonas aeruginosa
- D. Cryptococcus neoformans
Explanation: ***Bacillus anthracis*** - This description is classic for **cutaneous anthrax**, characterized by a **malignant pustule** or **eschar** that develops at the site of inoculation. - The context of handling **animal skins** (e.g., wool-sorter's disease) is a key epidemiological clue for _Bacillus anthracis_ infection. *Neisseria meningitidis* - Primarily causes **meningitis** and **meningococcemia**, involving a petechial or purpuric rash, not a single eschar or malignant pustule. - There is no direct association with handling animal skins. *Pseudomonas aeruginosa* - This bacterium is often associated with **opportunistic infections** in immunocompromised individuals, burn patients, or those with indwelling medical devices. - While it can cause skin lesions (e.g., **ecthyma gangrenosum**), these are distinct from the anthrax eschar and are not linked to animal skin exposure. *Cryptococcus neoformans* - A **fungus** that primarily causes **cryptococcal meningitis** or pulmonary infections, especially in immunocompromised individuals. - Skin manifestations, when they occur, are typically papules, nodules, or ulcers, not the classic **cutaneous anthrax eschar**.
Question 4: An 18-year-old man has facial and upper back lesions that have waxed and waned for the past 6 years. On physical examination, there are 0.3- to 0.9-cm comedones, erythematous papules, nodules, and pustules most numerous on the lower face and posterior upper trunk. Other family members have been affected by this condition at a similar age. The lesions worsen during a 5-day cruise to the Adriatic. Which of the following organisms is most likely to play a key role in the pathogenesis of these lesions?
- A. Propionibacterium acnes (Correct Answer)
- B. Herpes simplex virus type 1
- C. Group A β-hemolytic streptococcus
- D. Mycobacterium leprae
Explanation: ***Propionibacterium acnes*** (now *Cutibacterium acnes*) - The presence of **comedones, papules, nodules, and pustules** on the face and upper back in an 18-year-old is classic for **acne vulgaris**. - **_P. acnes_** is a commensal bacterium that proliferates in clogged hair follicles, contributing to inflammation and lesion formation in acne due to its lipolytic activity and immune-activating properties. *Herpes simplex virus type 1* - **HSV-1** typically causes **oral herpes (cold sores)** or **genital herpes**, characterized by painful vesicles and ulcers. - The described lesions (comedones, papules, nodules, pustules) are not characteristic of HSV-1 infection. *Group A β-hemolytic streptococcus* - **Group A Strep** causes infections like **pharyngitis (strep throat)**, **impetigo**, or **cellulitis**, which are typically acute and rapidly spreading. - Its presence is not associated with chronic, polymorphic lesions characteristic of acne. *Mycobacterium leprae* - **_M. leprae_** is the causative agent of **leprosy**, presenting with skin lesions, nerve damage, and other systemic effects. - The skin lesions of leprosy are typically macules, papules, or nodules with sensory loss, not the comedones and pustules seen in acne.
Question 5: What is the treatment for granuloma inguinale?
- A. Tetracycline
- B. Azithromycin (Correct Answer)
- C. Clarithromycin
- D. Streptomycin
Explanation: ***Azithromycin*** - **Azithromycin** is the recommended first-line treatment for **granuloma inguinale** (donovanosis) caused by *Klebsiella granulomatis*. - Current recommended regimens: **Azithromycin 1g orally once weekly** OR **500mg daily for at least 3 weeks** (until all lesions have completely healed). - Preferred due to excellent tissue penetration, good efficacy, and convenient dosing that improves patient compliance. *Tetracycline* - **Tetracycline** (500mg four times daily) was historically used but has been largely replaced by **doxycycline** (100mg twice daily) as the preferred tetracycline-class antibiotic. - While effective against *Klebsiella granulomatis*, it requires frequent dosing leading to poor adherence. - **Doxycycline** (not listed here) is actually considered a co-first-line option alongside azithromycin in current CDC guidelines. *Clarithromycin* - **Clarithromycin** is a macrolide antibiotic but is not a recommended first-line agent for granuloma inguinale. - Limited clinical data supports its use for this condition, and it is not included in standard treatment guidelines. - Azithromycin from the same macrolide class is preferred due to better-established efficacy. *Streptomycin* - **Streptomycin** is an aminoglycoside antibiotic primarily used for mycobacterial infections (e.g., tuberculosis, plague). - Not indicated for granuloma inguinale as *Klebsiella granulomatis* responds well to macrolides (azithromycin) and tetracyclines (doxycycline). - Requires parenteral administration and has significant toxicity concerns (ototoxicity, nephrotoxicity).
Question 6: A 35-year-old obese woman presents with recurrent lesions in both axilla in summer season. Wood lamp examination is shown. The diagnosis is:
- A. Ecthyma
- B. Erythrasma (Correct Answer)
- C. Impetigo contagiosa
- D. Bullous impetigo
Explanation: ***Erythrasma*** - Erythrasma is a superficial bacterial infection caused by **Corynebacterium minutissimum**, which commonly presents as red-brown patches in intertriginous areas like the axilla, especially in obese individuals and warm, humid conditions (summer season). - The distinctive **coral-red fluorescence under Wood's lamp** is due to porphyrin production by the bacteria, which is a classic diagnostic feature of erythrasma, as shown in the image. *Ecthyma* - Ecthyma is a deeper form of impetigo characterized by **ulcerative lesions with a thick, adherent crust** that extend into the dermis. - It is typically caused by *Streptococcus pyogenes* and sometimes *Staphylococcus aureus*, and would not exhibit coral-red fluorescence under Wood's lamp. *Impetigo contagiosa* - Impetigo contagiosa (non-bullous impetigo) presents with **honey-colored crusted lesions**, usually on the face and extremities. - While also a bacterial skin infection, it is typically caused by *Staphylococcus aureus* or *Streptococcus pyogenes* and does not show coral-red fluorescence under Wood's lamp. *Bullous impetigo* - Bullous impetigo is characterized by **flaccid bullae** (blisters) that rupture to form thin, varnish-like crusts, primarily caused by *Staphylococcus aureus* producing exfoliative toxins. - Similar to other forms of impetigo, it does not produce the coral-red fluorescence under Wood's lamp.
Question 7: A young man presents with skin lesions as shown in the image below. All of the following organisms can spread through dermal and subcutaneous lymphatics, except
- A. Sporothrix schenckii
- B. Staphylococcus aureus (Correct Answer)
- C. Nocardia asteroides
- D. Mycobacterium marinum
Explanation: ***Staphylococcus aureus*** - While *Staphylococcus aureus* can cause various skin infections, it primarily spreads through **direct extension** or the **bloodstream**, not typically through the dermal and subcutaneous lymphatics in a pattern like the one shown. - Infections like cellulitis, abscesses, and impetigo caused by *Staphylococcus aureus* are usually localized or spread via contiguous tissue, rather than forming **linear nodular lesions** along lymphatic channels. *Sporothrix schenckii* - This fungus is a classic cause of **sporotrichosis**, which often presents with **lymphocutaneous spread** following traumatic inoculation. - The image shows **linearly arranged subcutaneous nodules** proximally along the arm, characteristic of lymphatic dissemination, often seen in sporotrichosis. *Nocardia asteroides* - **Nocardia infections** can also cause **lymphocutaneous disease** with a similar appearance to sporotrichosis, especially in immunocompromised individuals. - It can lead to a **chain of subcutaneous nodules and abscesses** tracking along lymphatic vessels from the initial site of infection. *Mycobacterium marinum* - **Mycobacterium marinum** causes **fish tank granuloma** or **swimming pool granuloma** following skin trauma in contaminated water. - It characteristically produces **ascending lymphocutaneous nodules** along lymphatic channels, similar to sporotrichosis, creating a **sporotrichoid pattern**. - The infection typically starts as a papule at the inoculation site and spreads proximally along lymphatics.
Question 8: A child presents with grouped vesicles on an erythematous base on the buttocks. What is the most likely diagnosis?
- A. Bullous impetigo
- B. Dermatitis herpetiformis
- C. Pemphigus
- D. Herpes simplex (Correct Answer)
Explanation: ***Herpes simplex*** - Herpes simplex virus (HSV) classically presents with **grouped vesicles on an erythematous base**, which perfectly matches this clinical presentation. - In **children**, HSV commonly affects the **buttocks** through autoinoculation or direct contact, especially in the diaper area. - The lesions are typically **painful and pruritic**, and may be preceded by tingling or burning sensation. - Diagnosis is confirmed by **Tzanck smear** (multinucleated giant cells), **PCR**, or **viral culture**. - Treatment includes **acyclovir** or other antivirals, especially for severe or recurrent cases. *Dermatitis herpetiformis* - While DH does present with intensely pruritic, grouped vesicles on an erythematous base, it is **extremely rare in children** and typically presents in **adults (3rd-4th decade)**. - Classic sites include **extensor surfaces** (elbows, knees), scalp, and buttocks, but the pediatric presentation makes this diagnosis unlikely. - It is strongly associated with **celiac disease** and responds to **gluten-free diet** and **dapsone**. *Bullous impetigo* - Bullous impetigo presents with **flaccid bullae** that rupture to form **honey-colored crusts**, not grouped vesicles. - It is a **bacterial infection** caused by *Staphylococcus aureus* producing exfoliative toxin. - Common in **young children**, particularly in warm, humid conditions. *Pemphigus* - Pemphigus is **extremely rare in children** and causes **fragile bullae** that easily rupture, leading to erosions. - Typically affects **mucous membranes first** (oral cavity), then skin. - It is an **autoimmune blistering disease** with antibodies against desmoglein, causing intraepidermal acantholysis.
Question 9: A 22-year-old woman presents with multiple tender, erythematous nodules on her shins that developed over the past week. She reports having a sore throat 2 weeks ago. She also complains of joint pain and fatigue. Physical examination reveals raised, red, tender nodules on the anterior surface of both legs. Her temperature is 38.2°C. Which of the following is the most likely diagnosis?
- A. Cellulitis
- B. Erythema nodosum (Correct Answer)
- C. Sweet syndrome
- D. Superficial thrombophlebitis
Explanation: ***Erythema nodosum*** - The presentation of **tender, erythematous nodules on the shins**, following a preceding **sore throat**, with associated **joint pain and fatigue**, is highly characteristic of **erythema nodosum**. - It is a form of **panniculitis** typically triggered by infections (e.g., streptococcal pharyngitis), medications, or systemic diseases. *Cellulitis* - Characterized by a **warm, erythematous, swollen area** with poorly defined borders, often accompanied by pain and fever, but typically presents as a diffuse skin infection rather than distinct nodules. - While fever is present, the **nodular nature** of the lesions and their bilateral, symmetrical distribution are less consistent with cellulitis. *Sweet syndrome* - Also known as acute febrile neutrophilic dermatosis, it presents with **tender erythematous plaques or nodules** and **fever**, but typically has a more prominent **neutrophilic infiltrate** histologically. - Lesions of Sweet syndrome often appear on the **upper extremities, face, or neck**, and while it can affect the shins, the clinical picture here is more classic for erythema nodosum, especially given the history of sore throat. *Superficial thrombophlebitis* - Presents as a **palpable, tender, erythematous cord** along the course of a superficial vein, often with localized swelling and warmth. - The lesions are typically **linear or cord-like**, not discrete nodules scattered over the shins, and are directly related to a thrombosed vein.
Question 10: The following image shows a flaccid bulla. This finding is characteristically seen in:
- A. Pemphigus vegetans
- B. Pemphigus vulgaris (Correct Answer)
- C. Pemphigus erythematosus
- D. Bullous pemphigoid
Explanation: ***Pemphigus vulgaris*** - The image shows a **flaccid bulla** with purulent fluid, characteristic of **pemphigus vulgaris**. This condition is marked by autoantibodies against desmogleins 1 and 3, which are crucial for keratinocyte adhesion, leading to **intraepidermal blistering** and the **Nikolsky sign**. - The flaccid nature of the bulla, often leading to easy rupture and erosions, is a hallmark of superficial blistering in pemphigus vulgaris, caused by the **loss of cell-to-cell adhesion** within the epidermis. *Pemphigus vegetans* - This is a rare variant of pemphigus vulgaris characterized by **vegetating plaques** and **hyperkeratotic lesions**, particularly in intertriginous areas. - While it starts with bullae, the predominant feature is the development of fungating, vegetative lesions rather than the flaccid bulla seen here. *Pemphigus erythematosus* - Pemphigus erythematosus, also known as Senear-Usher syndrome, is considered a localized form of pemphigus foliaceus with features of **lupus erythematosus**. - It presents with **scaling, crusting, and erythematous lesions** resembling lupus, along with superficial bullae, typically on the face and scalp. *Bullous pemphigoid* - Bullous pemphigoid typically presents with **tense bullae** that are less prone to rupture, unlike the flaccid bulla shown in the image. - It is caused by autoantibodies against hemidesmosomal proteins (BP180 and BP230), resulting in **subepidermal blistering**, meaning the blister forms below the epidermis and is therefore more resilient.
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