Bacterial Skin Infections Practice Questions

Q: Which form of leprosy is considered the most unstable?

Borderline Borderline (BB). **Explanation:** The classification of leprosy follows the **Ridley-Jopling scale**, which is based on the host’s cell-mediated immunity (CMI). **Borderline Borderline (BB) leprosy** is considered the most unstable form because it represents a precarious midpoint on the immunological spectrum. Patients with BB leprosy do not stay in this stage for long; they almost always shift (downgrade) toward the lepromatous pole (BL/LL) if untreated, or shift (upgrade/reverse) toward the tuberculoid pole (BT) during a type 1 lepra reaction. **Analysis of Options:** * **Borderline Borderline (BB):** Correct. It is immunologically "on a knife-edge." It is characterized by "punched-out" or Swiss-cheese appearance lesions and is rarely seen in clinical practice because of its rapid transition to other forms. * **Borderline Tuberculoid (BT) & Borderline Lepromatous (BL):** While these are also "borderline" and can undergo reactions, they possess a more defined immunological stance than BB and are relatively more stable. * **Tuberculoid (TT) & Lepromatous (LL):** These are the **stable poles** of the spectrum. TT represents high CMI (localized disease), while LL represents low/absent CMI (generalized disease). They do not shift across the spectrum. **NEET-PG High-Yield Pearls:** * **Most common type in India:** Borderline Tuberculoid (BT). * **Stable poles:** TT and LL. * **Punched-out/Swiss-cheese lesions:** Pathognomonic for BB leprosy. * **Lepra Reactions:** Type 1 (Reversal) reactions are most common in borderline forms (BT, BB, BL), while Type 2 (ENL) is seen in BL and LL. * **Face sparing:** Typically seen in TT; the "immune-privileged" sites (axilla, groin, midline of back) are spared in LL.

Q: Tuberculosis verrucosa cutis is a form of:

Postprimary tuberculosis with good resistance. **Explanation:** Cutaneous tuberculosis is classified based on the mode of infection (exogenous vs. endogenous) and the host's immune status. **Tuberculosis Verrucosa Cutis (TVC)**, also known as "Prosector’s wart," occurs due to **exogenous inoculation** of *Mycobacterium tuberculosis* into the skin of a person who has **previously been infected** and has developed **strong cell-mediated immunity (CMI)**. Because the host has high resistance, the lesion remains localized, and the bacterial load is low (paucibacillary). **Analysis of Options:** * **Option C (Correct):** TVC is a **postprimary** infection because it occurs in sensitized individuals. The "good resistance" (high CMI) prevents systemic spread and results in the characteristic hyperkeratotic, verrucous (wart-like) plaque. * **Option A:** **Tuberculids** (e.g., Erythema induratum, Papulonecrotic tuberculid) are hypersensitivity reactions to internal TB; the organism cannot be cultured from the skin lesions. * **Option B:** **Primary tuberculosis** (e.g., Tuberculous Chancre) occurs in a non-sensitized individual with no prior immunity. * **Option C:** **Postprimary with poor resistance** describes conditions like **Scrofuloderma** or **Lupus Vulgaris** (moderate-to-good) or **Miliary TB** (very poor), where the body cannot effectively contain the spread. **High-Yield Clinical Pearls for NEET-PG:** * **Most common type** of cutaneous TB in India: **Lupus Vulgaris** (overall) or **Scrofuloderma** (in children). * **TVC Clinical Presentation:** Warty plaque, usually on the hands, knees, or buttocks. * **Diagnosis:** Mantoux test is strongly positive; Histopathology shows pseudoepitheliomatous hyperplasia and granulomas. * **Key Distinction:** Unlike Lupus Vulgaris, TVC **does not** show "apple-jelly nodules" on diascopy.

Q: What is the treatment of choice for chancroid?

Erythromycin. **Explanation:** **Chancroid** is a sexually transmitted infection caused by the Gram-negative coccobacillus ***Haemophilus ducreyi***. It is clinically characterized by painful genital ulcers (soft chancre) and painful inflammatory inguinal lymphadenopathy (buboes). **Why Erythromycin is correct:** Macrolides are the mainstay of treatment for chancroid. **Erythromycin** (500 mg four times daily for 7 days) is a classic drug of choice. However, current CDC guidelines also recommend a single dose of **Azithromycin** (1g orally) or **Ceftriaxone** (250mg IM) as first-line options due to better compliance. These drugs inhibit protein synthesis or cell wall synthesis of *H. ducreyi* effectively. **Why the other options are incorrect:** * **Penicillin:** *H. ducreyi* produces beta-lactamases, making it resistant to standard penicillins. * **Chloramphenicol:** While it has broad-spectrum activity, it is not used due to its potential for serious bone marrow toxicity and the availability of safer alternatives. * **Tetracyclines:** Although historically used, widespread resistance has developed, making them unreliable for treating chancroid. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Ulcers:** "Chancroid is **Do-cry** (*H. ducreyi*) because it is **painful**." (Contrast with Syphilis/Chancre, which is painless). * **School of Fish Appearance:** This is the characteristic Gram stain finding for *H. ducreyi*. * **Co-infection:** Always screen for HIV and Syphilis in patients diagnosed with Chancroid, as genital ulcers facilitate HIV transmission. * **First-line (Current):** Azithromycin (1g single dose) or Ceftriaxone (250mg IM).

Q: What is the most common type of leprosy?

Borderline Tuberculoid (BT). **Explanation:** In the Ridley-Jopling classification of Leprosy, the disease is viewed as a spectrum based on the host's cell-mediated immunity (CMI). **Why Borderline Tuberculoid (BT) is correct:** **Borderline Tuberculoid (BT)** is the most common clinical presentation of leprosy worldwide, particularly in India. It represents a state where the CMI is present but not strong enough to localize the infection completely (unlike TT). Patients typically present with a few asymmetrical, hypopigmented patches with satellite lesions and peripheral nerve involvement. Because the majority of patients fall into the "borderline" categories rather than the polar ends, BT emerges as the most frequent subtype encountered in clinical practice. **Analysis of Incorrect Options:** * **Tuberculoid (TT):** This is the stable polar form with high CMI. While common, it is less frequent than BT. It is characterized by a single, well-defined, anesthetic hairless patch. * **Mid-Borderline (BB):** This is the most unstable form of leprosy. It is clinically rare because patients rapidly shift (upgrade or downgrade) toward the BT or BL poles. * **Lepromatous (LL):** This is the stable polar form with minimal CMI and high bacterial load (multibacillary). While it has the most severe systemic involvement, its prevalence is lower than the BT subtype. **NEET-PG High-Yield Pearls:** * **Most common type in India:** Borderline Tuberculoid (BT). * **Most unstable type:** Mid-Borderline (BB). * **Type most prone to Type 1 Reaction:** BT and BL (Borderline spectrum). * **Type most prone to Type 2 Reaction (ENL):** BL and LL. * **Lepromin Test:** Strongly positive in TT, negative in LL. (Note: It is a prognostic test, not a diagnostic one).

Q: Jarisch Herxheimer reaction is commonly seen in which stage of syphilis?

Early syphilis. The **Jarisch-Herxheimer Reaction (JHR)** is an acute febrile response that occurs following the initiation of effective antimicrobial therapy (classically Penicillin) for spirochetal infections, most notably syphilis. ### **Why Early Syphilis is the Correct Answer** The reaction is triggered by the rapid release of lipoproteins, pyrogens, and cytokines (such as TNF-α, IL-6, and IL-8) from the lysis of a high burden of spirochetes (*Treponema pallidum*). * **Early syphilis** (Primary and Secondary stages) is characterized by a **high bacterial load** [2]. * JHR occurs in approximately **70–90% of patients with Secondary syphilis** and about 50% of those with Primary syphilis. * In contrast, late stages have a much lower density of organisms, making the reaction less frequent [2]. ### **Analysis of Incorrect Options** * **B & C (Late Congenital and Latent Syphilis):** These stages have a significantly lower treponemal burden compared to the secondary stage [2]. While JHR can occur, the incidence is much lower [1]. * **D (Cardiovascular Syphilis):** This is a form of tertiary syphilis [2]. While JHR is rare here, it can be life-threatening if it occurs (e.g., causing coronary ostial narrowing or aortic rupture), but it is not the "most common" stage for the reaction. ### **NEET-PG High-Yield Pearls** * **Clinical Features:** Fever, chills, headache, myalgia, and exacerbation of the syphilitic rash. * **Timing:** Usually starts within **2–8 hours** of treatment and resolves spontaneously within 24 hours [1]. * **Management:** It is **not** an allergic reaction to penicillin. Treatment is symptomatic (NSAIDs/Antipyretics). Do not stop the antibiotic. * **Prevention:** In cases of neurosyphilis or cardiovascular syphilis, **Corticosteroids** may be used to prevent a severe reaction. * **Other Diseases:** JHR is also seen in Borreliosis (Lyme disease/Relapsing fever) and Leptospirosis [1].

Q: A patient presents with a split papule at the corner of the mouth. What is the most likely diagnosis?

Secondary syphilis. **Explanation:** The **split papule** is a classic, high-yield clinical sign of **Secondary Syphilis**. It occurs when a syphilitic papule develops at a mucosal fold, most commonly the angle of the mouth (commissure) or the nasolabial fold. Due to the constant movement and friction at these sites, the papule becomes fissured or "split" down the center, often appearing as two halves of a papule facing each other. **Analysis of Options:** * **Secondary Syphilis (Correct):** Known as the "Great Imitator," its secondary stage is characterized by generalized lymphadenopathy and mucocutaneous lesions. The split papule is a specific morphological variant seen at the angles of the mouth. * **Recurrent Herpes Labialis:** Typically presents as a cluster of painful, grouped vesicles on an erythematous base ("cold sores"), usually at the vermilion border. It does not present as a solid split papule. * **Recurrent Herpetic Stomatitis:** This primarily affects the keratinized oral mucosa (hard palate and gingiva) as small ulcers; it is not characterized by fissured papules at the commissures. * **Increased Vertical Dimension:** This is a dental/prosthodontic term. Conversely, a *decreased* vertical dimension (often seen in edentulous patients) leads to **Angular Cheilitis** due to saliva accumulation in skin folds, but this presents as maceration and erythema, not a distinct split papule. **NEET-PG High-Yield Pearls:** * **Condyloma Lata:** Flat-topped, moist, highly infectious papules in intertriginous areas (also secondary syphilis). * **Palmoplantar Rash:** Secondary syphilis is a classic cause of copper-colored maculopapular rashes on the palms and soles. * **Lues Maligna:** A severe, pleomorphic form of secondary syphilis seen in HIV-positive patients. * **Diagnosis:** Screening is done via VDRL/RPR; confirmation via TPHA/FTA-ABS.

Q: A 27-year-old man develops a painless 1-cm sore on his penis. It appears ulcerated with a raised margin and minimal serous exudates. Which of the following is the most appropriate next step in the diagnosis?

serology. **Explanation:** The clinical presentation of a **painless, indurated ulcer with a raised margin** and minimal exudate on the genitalia is the classic description of a **Hard Chancre**, the hallmark of **Primary Syphilis** caused by *Treponema pallidum* [1]. **Why Serology is the correct answer:** In modern clinical practice, diagnosis relies on serological testing [1]. This is divided into: 1. **Nonspecific (Nontreponemal) tests:** VDRL and RPR (used for screening and monitoring treatment response) [1]. 2. **Specific (Treponemal) tests:** FTA-ABS and TPHA (used for confirmation) [1]. While **Dark-field microscopy** was historically the gold standard for early lesions, it is often unavailable or technically demanding. Therefore, serology remains the most appropriate and practical next step for diagnosis in the NEET-PG context. **Why other options are incorrect:** * **Biopsy:** Not indicated for suspected syphilis unless the lesion is atypical or fails to heal, as it is invasive and non-specific. * **Gram stain:** *T. pallidum* is a spirochete and does not take up Gram stain; it requires silver stains (e.g., Warthin-Starry) or dark-field microscopy. * **Ultrasound:** Has no role in the diagnosis of a cutaneous genital ulcer. **Clinical Pearls for NEET-PG:** * **Incubation Period:** 9–90 days (Average 3 weeks). * **Painful vs. Painless:** Syphilis (Painless) vs. Chancroid (Painful/Soft Chancre). * **Window Period:** Serology may be negative in the first 1–2 weeks of the chancre; if clinical suspicion is high, repeat testing is necessary [1]. * **Treatment:** Benzathine Penicillin G (2.4 million units IM) is the drug of choice.

Q: Type-II lepra reaction is found in which classification of leprosy?

Lepromatous (LL). **Explanation:** Type-II Lepra Reaction, also known as **Erythema Nodosum Leprosum (ENL)**, is a Type-III hypersensitivity reaction (immune-complex mediated). It occurs exclusively in patients with a high bacillary load and low cell-mediated immunity (CMI). **Why Lepromatous (LL) is correct:** In the Ridley-Jopling classification, **Lepromatous (LL)** and **Borderline Lepromatous (BL)** leprosy are characterized by an abundance of *Mycobacterium leprae* (high Bacteriological Index). When treatment begins or during physiological stress, there is a massive release of antigens. These antigens combine with circulating antibodies to form immune complexes that deposit in tissues, leading to the systemic inflammatory features of ENL. **Why the other options are incorrect:** * **Tuberculoid (TT) and Borderline Tuberculoid (BT):** These poles have high CMI and very few bacilli (paucibacillary). Because there is an insufficient antigenic load to form significant immune complexes, Type-II reactions do not occur. Instead, these types are prone to **Type-I (Reversal) Reactions**, which are Type-IV hypersensitivity reactions. * **Borderline (BB):** While BB can occasionally transition toward the lepromatous pole, it is most classically associated with severe Type-I reactions due to its immunological instability. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Features:** Characterized by tender, evanescent, erythematous nodules, fever, lymphadenopathy, arthritis, and iridocyclitis. * **Drug of Choice:** **Thalidomide** is the gold standard for Type-II reactions. Steroids and Clofazimine are also used. * **Timing:** Unlike Type-I reactions (which often occur shortly after starting MDT), Type-II reactions can occur before, during, or even years after completing treatment. * **Key Lab Finding:** Neutrophilic leukocytosis and increased ESR/CRP.

Q: Cell-mediated immunity is maximally suppressed in which of the following conditions?

Lucio's Leprosy (LL). ### Explanation The clinical spectrum of Leprosy (Hansen’s Disease) is determined by the host's **Cell-Mediated Immunity (CMI)** against *Mycobacterium leprae*. This spectrum ranges from high resistance (Tuberculoid) to negligible resistance (Lepromatous). **Why Lucio’s Leprosy (LL) is correct:** Lucio’s Leprosy is a variant of **Lepromatous Leprosy (LL)**. In the LL pole, there is a **selective anergy** (complete absence of CMI) specifically against *M. leprae* antigens. This leads to uncontrolled bacillary multiplication, high bacterial indices, and a negative Lepromin test. While the humoral (antibody) response is exaggerated, it is ineffective at killing the intracellular bacilli, making LL the state of maximum CMI suppression. **Analysis of Incorrect Options:** * **Tuberculoid (TT):** This represents the opposite pole where CMI is **maximal**. The body effectively contains the infection, resulting in few lesions and a strongly positive Lepromin test. * **Borderline Tuberculoid (BT):** CMI is present but slightly diminished compared to TT. It is an unstable clinical state but far from the total suppression seen in LL. * **Indeterminate:** This is the early stage of the disease where the immune response has not yet polarized. CMI is not yet "suppressed"; it is simply evolving. **High-Yield Clinical Pearls for NEET-PG:** * **Th1 vs. Th2:** TT is associated with a **Th1 response** (IL-2, IFN-γ), while LL is associated with a **Th2 response** (IL-4, IL-5, IL-10). * **Lepromin Test:** It is a measure of CMI, not a diagnostic test. It is **Positive in TT** and **Negative in LL**. * **Lucio’s Phenomenon:** A rare, severe necrotizing vasculitis seen specifically in Lucio’s Leprosy, characterized by painful, jagged ulcerations. * **Foam Cells (Virchow cells):** Characteristic histological finding in LL due to macrophages laden with lepra bacilli.

Q: What is the drug of choice in Type I Lepra reaction with severe neuritis?

Systemic steroid. **Explanation:** **Type I Lepra Reaction (Reversal Reaction)** is a Delayed Type Hypersensitivity (Type IV) reaction occurring in borderline cases of leprosy. It is characterized by acute inflammation of existing skin lesions and, more critically, **acute neuritis** (nerve pain, tenderness, and loss of function). **Why Systemic Steroids are the Correct Choice:** The primary goal in managing Type I reactions, especially with **severe neuritis**, is to rapidly suppress cell-mediated inflammation to prevent permanent nerve damage and physical disability. **Systemic Corticosteroids (e.g., Prednisolone)** are the gold standard because they provide rapid anti-inflammatory and immunosuppressive action. The standard regimen usually starts at 40–60 mg/day, tapered over several months. **Analysis of Incorrect Options:** * **B. Clofazimine:** While it has anti-inflammatory properties and is used in Type II reactions (ENL) to help taper steroids, it is too slow-acting for the acute management of severe neuritis in Type I reactions. * **C. Thalidomide:** This is the **drug of choice for Type II Lepra Reaction (ENL)**. It is ineffective in Type I reactions because it does not address the Type IV hypersensitivity mechanism. * **D. Chloroquine:** This is a third-line agent occasionally used for mild Type II reactions (ENL) but has no role in managing Type I reactions or acute neuritis. **High-Yield Clinical Pearls for NEET-PG:** * **Type I Reaction:** Type IV Hypersensitivity; occurs in BT, BB, BL; key feature is **Neuritis**; DOC: **Steroids**. * **Type II Reaction (ENL):** Type III Hypersensitivity; occurs in BL, LL; key feature is **Erythema Nodosum** (tender nodules); DOC: **Thalidomide** (Steroids are also used, but Thalidomide is specific). * **Nerve Involvement:** If a patient on MDT develops new sensory/motor loss without skin changes, suspect "Silent Neuritis"—this also requires urgent systemic steroids.

Question 1

Which form of leprosy is considered the most unstable?

Accepted Answer

Borderline Borderline (BB)

Answer

Borderline Lepromatous (BL)

Answer

Borderline Tuberculoid (BT)

Answer

Tuberculoid Tuberculoid (TT)

Question 2

Tuberculosis verrucosa cutis is a form of:

Accepted Answer

Postprimary tuberculosis with good resistance

Answer

Tuberculid

Answer

Primary tuberculosis

Answer

Postprimary tuberculosis with poor resistance

Question 3

What is the treatment of choice for chancroid?

Accepted Answer

Erythromycin

Answer

Penicillin

Answer

Chloramphenicol

Answer

Tetracyclines

Question 4

What is the most common type of leprosy?

Accepted Answer

Borderline Tuberculoid (BT)

Answer

Tuberculoid (TT)

Answer

Mid-Borderline (BB)

Answer

Lepromatous (LL)

Question 5

Jarisch Herxheimer reaction is commonly seen in which stage of syphilis?

Accepted Answer

Early syphilis

Answer

Late congenital syphilis

Answer

Latent syphilis

Answer

Syphilis of the cardiovascular system

Question 6

A patient presents with a split papule at the corner of the mouth. What is the most likely diagnosis?

Accepted Answer

Secondary syphilis

Answer

Recurrent herpes labialis

Answer

Recurrent herpetic stomatitis

Answer

Increased vertical dimension

Question 7

A 27-year-old man develops a painless 1-cm sore on his penis. It appears ulcerated with a raised margin and minimal serous exudates. Which of the following is the most appropriate next step in the diagnosis?

Accepted Answer

serology

Answer

biopsy

Answer

Gram stain

Answer

ultrasound

Question 8

Type-II lepra reaction is found in which classification of leprosy?

Accepted Answer

Lepromatous (LL)

Answer

Borderline (BB)

Answer

Borderline tuberculoid (BT)

Answer

Tuberculoid (TT)

Question 9

Cell-mediated immunity is maximally suppressed in which of the following conditions?

Accepted Answer

Lucio's Leprosy (LL)

Answer

Borderline Tuberculoid (BT)

Answer

Tuberculoid (TT)

Answer

Indeterminate

Question 10

What is the drug of choice in Type I Lepra reaction with severe neuritis?

Accepted Answer

Systemic steroid

Answer

Clofazimine

Answer

Thalidomide

Answer

Chloroquine

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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