Bacterial Skin Infections Practice Questions

Q: A farmer presents with a lesion on the leg. Which of the following is the most likely diagnosis?

Tuberculosis verrucosa cutis. ***Tuberculosis verrucosa cutis*** - **Farmer's occupation** creates high risk for inoculation injury with **Mycobacterium tuberculosis**, leading to this **verrucous, warty skin lesion** typically on exposed areas like legs. - Characterized by **hyperkeratotic, warty plaques** with minimal inflammation, often called "**prosector's wart**" when occurring in healthcare workers. *Verruca vulgaris* - Caused by **human papillomavirus (HPV)**, not associated with occupational farming activities or tuberculosis exposure. - Typically presents as **well-demarcated papules** with **black dots** (thrombosed capillaries), unlike the hyperkeratotic appearance of TVC. *Mycetoma* - Presents as **chronic granulomatous infection** with **multiple sinuses** discharging colored grains, not a single verrucous lesion. - Caused by **fungi or actinomycetes**, typically affecting the **foot** (Madura foot) rather than presenting as warty leg lesions. *Lichen planus hypertrophicus* - **Autoimmune condition** with **violaceous, polygonal papules** showing **Wickham's striae**, unrelated to occupational exposure. - Typically affects **flexural surfaces** and mucous membranes, not associated with farming or tuberculosis infection.

Q: Apple jelly nodules on diascopy are characteristic of which condition?

Lupus vulgaris. **Explanation:** **Lupus Vulgaris (Correct Answer):** Lupus vulgaris is the most common form of chronic, progressive cutaneous tuberculosis. It occurs in individuals with a high degree of cell-mediated immunity. The characteristic lesion is a reddish-brown plaque that expands peripherally. When a glass slide is pressed against the lesion (**diascopy**), the vascular congestion is blanched, revealing yellowish-brown, translucent foci known as **"apple jelly nodules."** These nodules represent the underlying granulomatous pathology (tubercles) in the dermis. **Incorrect Options:** * **Tinea versicolor:** A fungal infection caused by *Malassezia furfur*. It presents as hypo- or hyperpigmented scaly macules. Diagnosis is confirmed by a "spaghetti and meatballs" appearance on KOH mount or yellow-orange fluorescence under Wood’s lamp. * **Erythrasma:** A bacterial infection caused by *Corynebacterium minutissimum*. It typically involves intertriginous areas and shows a characteristic **coral-red fluorescence** under Wood’s lamp due to porphyrin production. * **Vitiligo:** An autoimmune condition causing depigmentation. Diascopy is not diagnostic; however, Wood’s lamp examination shows a bright "milk-white" fluorescence. **High-Yield Clinical Pearls for NEET-PG:** * **Diascopy:** Used to differentiate between purpura (extravasated blood, does not blanch) and erythema (dilated capillaries, blanches). * **Lupus Vulgaris Complication:** The most serious long-term complication is the development of **Squamous Cell Carcinoma** (Marjolin’s ulcer) within the scar. * **Other "Apple Jelly" associations:** While classic for Lupus Vulgaris, apple jelly nodules can also be seen in **Sarcoidosis** and **Leishmaniasis**.

Q: What is the recommended duration for the treatment of multibacillary leprosy?

12 months. **Explanation:** The treatment of Leprosy follows the World Health Organization (WHO) Multi-Drug Therapy (MDT) guidelines. The correct duration for **Multibacillary (MB) Leprosy** is **12 months**. **1. Why 12 months is correct:** In 1998, the WHO shortened the treatment duration for MB leprosy from 24 months to 12 months. This change was based on clinical trials showing that a 12-month regimen of Rifampicin, Clofazimine, and Dapsone was sufficient to achieve a cure and prevent relapse, while significantly improving patient compliance. **2. Analysis of Incorrect Options:** * **24 months (Option A):** This was the standard duration for MB leprosy prior to 1998. While some clinicians still consider it for patients with a very high Bacterial Index (BI >4+), it is no longer the standard WHO recommendation. * **18 months (Option B):** There is no standard WHO regimen for leprosy that lasts 18 months; this is a distractor. * **6 months (Option D):** This is the standard duration for **Paucibacillary (PB) Leprosy**, which involves fewer lesions and a lower bacterial load. **High-Yield Clinical Pearls for NEET-PG:** * **MB MDT Regimen:** Rifampicin (600mg once monthly, supervised), Clofazimine (300mg once monthly supervised + 50mg daily), and Dapsone (100mg daily). * **PB MDT Regimen:** Rifampicin (600mg once monthly) and Dapsone (100mg daily) for 6 months. * **Classification:** MB is defined by >5 skin lesions, >1 nerve involvement, or a positive skin smear. PB is 1–5 lesions and only 1 nerve involved. * **Accompanied MDT (A-MDT):** Providing the full course of treatment at the first visit to ensure completion in mobile populations.

Q: A farmer presents with a lesion on the leg. Which of the following is the most likely diagnosis?

Tuberculosis verrucosa cutis. ***Tuberculosis verrucosa cutis*** - Occurs through **inoculation** in individuals with high immunity to TB, commonly in **farmers** and **laborers** exposed to contaminated soil. - Presents as a **verrucous plaque** on extremities, typically the **legs or hands**, with characteristic **warty appearance**. *Verruca vulgaris* - Caused by **human papillomavirus (HPV)** and lacks specific **occupational association** with farming activities. - Usually appears as **discrete papules** with **black dots** (thrombosed capillaries), not large verrucous plaques. *Mycetoma* - Characterized by the **triad** of **tumefaction**, **sinuses**, and **grains** discharged from sinus tracts. - Involves **deeper subcutaneous tissues** and bone, presenting with significant **swelling** and **deformity**. *Lichen planus hypertrophicus* - Shows **violaceous polygonal papules** that are **pruritic** and typically affect **flexural surfaces**. - Lacks **occupational predisposition** and has different **morphological characteristics** compared to verrucous lesions.

Q: In a diagnosed lepromatous leprosy patient, treatment was started. After intake of the drug, skin lesions and fever develop within a few days. Which type of hypersensitivity reaction leads to this manifestation?

Type 3. **Explanation:** The clinical scenario describes **Erythema Nodosum Leprosum (ENL)**, also known as a **Type 2 Lepra Reaction**. This typically occurs in patients with Lepromatous Leprosy (LL) or Borderline Lepromatous (BL) leprosy, often triggered by the initiation of multidrug therapy (MDT). **Why Type 3 Hypersensitivity is Correct:** ENL is a classic example of a **Type 3 (Immune-complex mediated) hypersensitivity reaction**. The rapid killing of a high load of *Mycobacterium leprae* bacilli by drugs releases a large amount of bacterial antigens into the circulation. these antigens combine with circulating antibodies to form **immune complexes**, which deposit in blood vessel walls, activating the complement system and leading to systemic vasculitis. This manifests clinically as painful erythematous nodules, high-grade fever, malaise, and occasionally organ involvement (neuritis, arthritis, or iridocyclitis). **Why Incorrect Options are Wrong:** * **Type 4 (Delayed-type):** This is the mechanism behind **Type 1 Lepra Reactions (Reversal Reactions)**, seen in borderline cases. It involves a cell-mediated immune response, not immune complexes. * **Type 2 (Antibody-dependent):** This involves antibodies directed against antigens on specific cell surfaces (e.g., hemolytic anemia), which is not the pathology of ENL. * **Type 1 (Immediate):** This is IgE-mediated (e.g., anaphylaxis/urticaria) and is not associated with lepra reactions. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for ENL:** **Thalidomide** is the most effective treatment. Oral corticosteroids are used for milder cases or when thalidomide is contraindicated. * **Type 1 Reaction vs. Type 2 Reaction:** Type 1 occurs in paucibacillary/borderline cases (Type 4 hypersensitivity); Type 2 occurs in multibacillary cases (Type 3 hypersensitivity). * **Clofazimine:** This component of MDT has anti-inflammatory properties that help prevent and treat ENL.

Q: What is the best method of treatment for ulnar nerve abscess in case of leprosy?

Incision and drainage. **Explanation:** The management of nerve involvement in leprosy is critical to prevent permanent disability. When a patient presents with a **nerve abscess** (most commonly involving the ulnar nerve), it represents a localized collection of caseous material within the nerve sheath. **1. Why Incision and Drainage (I&D) is correct:** A nerve abscess is a surgical emergency in the context of leprosy. The accumulation of pus increases **intraneural pressure**, which leads to rapid ischemia and irreversible destruction of nerve fibers. Medical management alone cannot evacuate the collection. Therefore, **longitudinal incision of the nerve sheath (epineurotomy) and drainage** of the abscess is the definitive treatment to decompress the nerve and preserve motor and sensory function. **2. Why other options are incorrect:** * **High dose steroids (Option A):** While steroids are the mainstay for treating *Type 1 reactions* (neuritis), they cannot drain a physical collection of pus. They are used post-operatively to reduce edema but are not the primary treatment for an abscess. [1] * **Thalidomide (Option C):** This is the drug of choice for *Type 2 reactions (Erythema Nodosum Leprosum)*. It has no role in treating a localized nerve abscess. * **High dose Clofazimine (Option D):** Clofazimine has anti-inflammatory properties used in chronic ENL, but it is ineffective for the acute mechanical compression caused by an abscess. [2] **Clinical Pearls for NEET-PG:** * **Most common nerve involved in Leprosy:** Ulnar nerve. * **Most common nerve involved in Nerve Abscess:** Ulnar nerve. * **Steroid of choice for Lepra reactions:** Prednisolone. * **Silent Neuritis:** Nerve damage occurring without overt symptoms of inflammation; also managed with steroids. * **Surgical indication:** If there is no improvement in nerve function after 4–6 weeks of optimal steroid therapy, surgical decompression is indicated.

Q: Which of the following tests is NOT used for the diagnosis of leprosy?

Lepromin test. In leprosy management, it is crucial to distinguish between **diagnosis** and **prognosis**. **Why Option A (Lepromin Test) is the correct answer:** The Lepromin test is **not** a diagnostic test. It cannot confirm if a patient has leprosy because it is often negative in the most severe form (lepromatous leprosy) and can be positive in healthy individuals due to cross-reactivity with BCG or environmental mycobacteria. Instead, it is used for: 1. **Classification:** To categorize leprosy into Tuberculoid (Positive) or Lepromatous (Negative). 2. **Prognosis:** To assess the patient’s cell-mediated immunity (CMI) against *M. leprae*. 3. **Assessment of Resistance:** To check the immune status of an individual. **Why the other options are incorrect (Diagnostic Methods):** * **Slit Skin Smear (B):** The gold standard for identifying Acid-Fast Bacilli (AFB) using Ziehl-Neelsen staining. It is essential for calculating the Bacteriological Index (BI). * **Fine Needle Aspiration Cytology (C):** A reliable tool for sampling cells from enlarged nerves or skin nodules to identify granulomas and bacilli. * **Skin Biopsy (D):** The definitive method for histopathological confirmation, showing characteristic nerve involvement and granuloma patterns. **High-Yield Clinical Pearls for NEET-PG:** * **Cardinal Signs:** Diagnosis is primarily clinical based on: (1) Hypopigmented patches with sensory loss, (2) Thickened peripheral nerves, and (3) Positive skin smears. * **Fernandez Reaction:** Early reading of Lepromin test (at 48 hours); indicates delayed hypersensitivity. * **Mitsuda Reaction:** Late reading (at 21 days); indicates cell-mediated immunity. * **Ridley-Jopling Scale:** The standard 5-group classification system based on clinical, immunological, and histopathological features.

Q: Which of the following is NOT a characteristic of secondary syphilis?

It presents with vesicular bullous lesions.. Secondary syphilis is the systemic stage of infection caused by *Treponema pallidum*, occurring 4–10 weeks after the primary chancre. [1] ### **Why Option C is the Correct Answer** Syphilis is famously known as the **"Great Mimicker"** because it can present with almost any type of rash (macular, papular, or pustular) [1]. However, a key diagnostic rule in adult syphilis is that **it never presents with vesicular or bullous (blistering) lesions.** If a patient presents with a generalized blistering rash, syphilis can be clinically ruled out. * *Exception:* Vesiculobullous lesions are only seen in **Congenital Syphilis** (Pemphigus syphiliticus). ### **Analysis of Incorrect Options** * **A. It may be asymptomatic:** While secondary syphilis typically presents with a rash, some patients may have a "latent" transition where clinical signs are minimal or resolve spontaneously while the serology remains positive [1]. * **B. It usually involves palms and soles:** This is a high-yield clinical hallmark. A copper-red, maculopapular rash involving the palms and soles is highly suggestive of secondary syphilis [1]. * **D. Lymphadenopathy is common:** Generalized, painless, non-suppurative lymphadenopathy (especially epitrochlear nodes) is a classic feature of this stage [1]. ### **NEET-PG High-Yield Pearls** * **Condyloma Lata:** Highly infectious, moist, flat-topped papules found in intertriginous areas (e.g., axilla, perineum) [1]. * **Lues Maligna:** A rare, severe form of secondary syphilis with pleomorphic, necrotic ulcers seen in immunocompromised (HIV) patients. * **Snail Track Ulcers:** Mucous patches in the oropharynx. * **Diagnosis:** Screening is done via **VDRL/RPR** (non-specific); confirmation requires **FTA-ABS/TPHA** (specific).

Q: Type 2 lepra reaction occurs in which form of leprosy?

Multi bacillary leprosy. **Explanation:** **Type 2 Lepra Reaction**, also known as **Erythema Nodosum Leprosum (ENL)**, is a Type III hypersensitivity reaction (immune-complex mediated). It occurs due to the deposition of antigen-antibody complexes in tissues, leading to systemic inflammatory symptoms. **Why Option B is correct:** Type 2 reactions occur exclusively in patients with a high bacterial load, specifically those on the lepromatous end of the spectrum (**Lepromatous Leprosy (LL)** and **Borderline Lepromatous (BL)**). These forms are classified as **Multibacillary (MB) leprosy**. The high density of *Mycobacterium leprae* antigens reacts with circulating antibodies to form the immune complexes that trigger the reaction. **Why other options are incorrect:** * **Option A (Paucibacillary):** Paucibacillary leprosy (TT and BT) is characterized by high cell-mediated immunity and a very low bacterial load. Since there are insufficient antigens to form significant immune complexes, Type 2 reactions do not occur here. Instead, these patients are prone to **Type 1 reactions** (Type IV hypersensitivity). * **Option C & D:** These are incorrect as the reaction is specific to the bacterial load status of the patient. **NEET-PG High-Yield Pearls:** * **Clinical Presentation:** Characterized by tender, evanescent, erythematous nodules, high-grade fever, malaise, and systemic involvement (iridocyclitis, neuritis, arthritis, and orchitis). * **Timing:** Usually occurs during or after the initiation of Multi-Drug Therapy (MDT), as killing the bacilli releases massive amounts of antigen. * **Drug of Choice:** **Thalidomide** is the most effective treatment for Type 2 reactions. Oral corticosteroids and Clofazimine are also used. * **Key Distinction:** Type 1 reaction = Delayed Hypersensitivity (Type IV); Type 2 reaction = Immune Complex Mediated (Type III).

Q: Pitted keratolysis affects which of the following areas?

Palm and soles. **Explanation:** **Pitted keratolysis** is a superficial bacterial infection of the stratum corneum, primarily caused by **Kytococcus sedentarius** (formerly *Micrococcus*), *Corynebacterium* species, or *Actinomyces*. 1. **Why Option A is correct:** The bacteria produce **extracellular serine proteases** that digest the keratin of the stratum corneum. This process requires a moist, occlusive environment, which is why it characteristically involves the **weight-bearing areas of the soles** (and occasionally the palms). The digestion of keratin results in the pathognomonic "punched-out" pits (1–7 mm) seen clinically. 2. **Why Options B and C are incorrect:** * **Face:** The facial skin is thinner and lacks the thick stratum corneum required for these specific bacteria to thrive and create deep pits. * **Nails:** This is an infection of the keratinized skin (stratum corneum), not the nail plate (onycho-). 3. **High-Yield Clinical Pearls for NEET-PG:** * **Triad of Presentation:** Hyperhidrosis (excessive sweating), Bromhidrosis (foul odor due to sulfur compounds), and non-inflammatory punched-out pits. * **Risk Factors:** Occlusive footwear (boots), tropical climates, and prolonged immersion in water. * **Diagnosis:** Primarily clinical; Wood’s lamp may occasionally show coral-red fluorescence (if *Corynebacterium* is involved). * **Treatment:** Topical antibiotics like **Clindamycin, Erythromycin, or Mupirocin**, combined with measures to keep the feet dry (e.g., aluminum chloride hexahydrate).

Question 1

A farmer presents with a lesion on the leg. Which of the following is the most likely diagnosis?

Accepted Answer

Tuberculosis verrucosa cutis

Answer

Verruca vulgaris

Answer

Mycetoma

Answer

Lichen planus hypertrophicus

Question 2

Apple jelly nodules on diascopy are characteristic of which condition?

Accepted Answer

Lupus vulgaris

Answer

Tinea versicolor

Answer

Erythrasma

Answer

Vitiligo

Question 3

What is the recommended duration for the treatment of multibacillary leprosy?

Accepted Answer

12 months

Answer

24 months

Answer

18 months

Answer

6 months

Question 4

A farmer presents with a lesion on the leg. Which of the following is the most likely diagnosis?

Accepted Answer

Tuberculosis verrucosa cutis

Answer

Verruca vulgaris

Answer

Mycetoma

Answer

Lichen planus hypertrophicus

Question 5

In a diagnosed lepromatous leprosy patient, treatment was started. After intake of the drug, skin lesions and fever develop within a few days. Which type of hypersensitivity reaction leads to this manifestation?

Accepted Answer

Type 3

Answer

Type 4

Answer

Type 2

Answer

Type 1

Question 6

What is the best method of treatment for ulnar nerve abscess in case of leprosy?

Accepted Answer

Incision and drainage

Answer

High dose of steroid

Answer

Thalidomide

Answer

High dose of clofazamine

Question 7

Which of the following tests is NOT used for the diagnosis of leprosy?

Accepted Answer

Lepromin test

Answer

Slit skin smear

Answer

Fine needle aspiration cytology

Answer

Skin biopsy

Question 8

Which of the following is NOT a characteristic of secondary syphilis?

Accepted Answer

It presents with vesicular bullous lesions.

Answer

It may be asymptomatic.

Answer

It usually involves palms and soles.

Answer

Lymphadenopathy is common.

Question 9

Type 2 lepra reaction occurs in which form of leprosy?

Accepted Answer

Multi bacillary leprosy

Answer

Pauci bacillary leprosy

Answer

Both of the above

Answer

None of the above

Question 10

Pitted keratolysis affects which of the following areas?

Accepted Answer

Palm and soles

Answer

Face

Answer

Nails

Answer

All of the above

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

On this page

Practice by Chapter

Want unlimited practice?