Bacterial Skin Infections Practice Questions

Q: Which subtype of leprosy has the maximum number of TH1 cells?

Tuberculoid (TT). In leprosy, the clinical presentation is determined by the host's **Cell-Mediated Immunity (CMI)** against *Mycobacterium leprae*. This response is governed by the balance between **Th1** and **Th2** helper T-cells. ### Why Tuberculoid (TT) is Correct: **Tuberculoid Leprosy (TT)** represents the high-resistance end of the Ridley-Jopling spectrum. In these patients, the body mounts a vigorous **Th1-mediated immune response**. Th1 cells secrete pro-inflammatory cytokines like **IL-2 and IFN-γ**, which activate macrophages to kill the bacilli. Because the Th1 response is at its peak, the bacterial load is very low (paucibacillary), and the Mitsuda skin test is strongly positive. ### Why the Other Options are Incorrect: * **Lepromatous (LL):** This is the opposite end of the spectrum. Here, the immune response is dominated by **Th2 cells**, which secrete cytokines like **IL-4, IL-5, and IL-10**. This suppresses CMI and promotes antibody production, which is ineffective against intracellular *M. leprae*, leading to high bacterial loads (multibacillary). * **Borderline (BB) and Borderline Leprosy:** These represent the immunologically unstable middle of the spectrum. They have a mixture of Th1 and Th2 responses but never reach the maximal Th1 levels seen in polar Tuberculoid leprosy. ### High-Yield Clinical Pearls for NEET-PG: * **Th1 Response (TT):** High CMI, low bacilli, positive Lepromin test, cytokines: **IL-2, IFN-γ, IL-12**. * **Th2 Response (LL):** Low CMI, high bacilli, negative Lepromin test, cytokines: **IL-4, IL-5, IL-10**. * **Histology:** TT shows well-formed granulomas with epithelioid cells and many lymphocytes; LL shows "foamy macrophages" (Virchow cells) packed with bacilli (globi). * **Mnemonic:** **T**uberculoid = **T**h1 = **T**ight (strong) immunity.

Q: A young boy has a single scaly, hypoanaesthetic patch over the hand plus thickened ulnar nerve. What is the diagnosis?

Tuberculoid leprosy. ### Explanation The clinical presentation of a **single, well-defined, hypoanaesthetic patch** associated with a **thickened peripheral nerve** is the classic hallmark of **Tuberculoid Leprosy (TT)**. #### Why Tuberculoid Leprosy is Correct: In the Ridley-Jopling classification, Tuberculoid Leprosy represents the pole with **high cell-mediated immunity (CMI)**. The body’s strong immune response limits the disease to a few lesions (usually 1–3). * **Skin Lesion:** Typically a single, large, erythematous or hypopigmented patch with well-defined borders and a scaly surface. * **Sensory Loss:** Due to intense inflammation within the dermal nerves, anesthesia (loss of sensation) is early and profound. * **Nerve Involvement:** Asymmetric, early, and severe nerve thickening is characteristic. #### Why Other Options are Incorrect: * **Lepromatous Leprosy (LL):** Represents the low CMI pole. It presents with **multiple, symmetrical** macules, papules, or nodules. Sensory loss and nerve thickening occur very late in the disease. * **Indeterminate Leprosy:** This is the earliest stage. It usually presents as a single, vaguely defined hypopigmented macule with **no or minimal sensory loss** and no nerve thickening. * **Borderline Leprosy (BT/BB/BL):** These cases show more numerous lesions (usually 3–10) than TT. While BT (Borderline Tuberculoid) is similar to TT, the presence of a single lesion and profound anesthesia strongly points toward the polar Tuberculoid end. #### NEET-PG High-Yield Pearls: * **Cardinal Signs of Leprosy (WHO):** 1. Hypopigmented/erythematous patch with loss of sensation; 2. Thickened peripheral nerves; 3. Positive skin smear for Acid Fast Bacilli. * **Lepromin Test:** Strongly **positive** in Tuberculoid (TT) and **negative** in Lepromatous (LL). * **First Sensation Lost:** Temperature (cold followed by hot), followed by touch, pain, and deep pressure. * **Most Common Nerve Involved:** Ulnar nerve.

Q: What is most important in establishing the diagnosis of leprosy?

Slit smear for AFB. **Explanation:** The diagnosis of leprosy (Hansen’s disease) is primarily clinical, but the gold standard for **definitive confirmation** and classification is the demonstration of *Mycobacterium leprae*. **Why Slit Skin Smear (SSS) is the correct answer:** While leprosy is often diagnosed based on clinical signs, the **Slit Skin Smear for Acid-Fast Bacilli (AFB)** provides objective bacteriological evidence. It is essential for calculating the Bacteriological Index (BI) and Morphological Index (MI), which help distinguish between Paucibacillary (PB) and Multibacillary (MB) cases, thereby guiding the duration of Multi-Drug Therapy (MDT). **Analysis of Incorrect Options:** * **Evidence of neural involvement:** While thickened nerves and sensory loss are cardinal signs of leprosy, they can also occur in other neuropathies (e.g., diabetes, amyloidosis). It is a diagnostic criterion but less definitive than visualizing the bacilli. * **Hypopigmented patches:** This is a common presenting feature but is non-specific. Differential diagnoses include Pityriasis alba, Vitiligo, and Tinea versicolor. * **Positive Lepromin Test:** This is **not a diagnostic test**. It is used to measure the patient's cell-mediated immunity (CMI) against *M. leprae* to classify the type of leprosy (positive in Tuberculoid, negative in Lepromatous) and determine prognosis. **High-Yield Clinical Pearls for NEET-PG:** * **WHO Cardinal Signs:** (1) Hypopigmented/reddish patches with loss of sensation, (2) Thickened peripheral nerves, (3) Positive SSS for AFB. Presence of any **one** is diagnostic. * **Most common nerve involved:** Ulnar nerve. * **Biopsy Gold Standard:** Nerve biopsy is the most definitive for Pure Neuritic Leprosy. * **Staining:** Modified Ziehl-Neelsen stain (using 5% $H_2SO_4$ instead of 20% as *M. leprae* is less acid-fast than *M. tuberculosis*).

Q: Milian's ear sign is seen in which of the following conditions?

Erysipelas. **Explanation:** **Milian’s Ear Sign** is a classic clinical diagnostic feature used to differentiate between **Erysipelas** and **Cellulitis**. 1. **Why Erysipelas is correct:** Erysipelas is a superficial bacterial infection (most commonly caused by Group A *Streptococcus*) involving the upper dermis and superficial lymphatics. Because the pinna of the ear consists of skin tightly bound to cartilage with **no subcutaneous fat**, it can only be involved by superficial infections like erysipelas. When the ear is involved, it is called Milian’s Ear Sign. 2. **Why other options are incorrect:** * **Cellulitis:** This is a deeper infection involving the deep dermis and **subcutaneous fat**. Since the pinna lacks subcutaneous fat, cellulitis cannot involve the earlobe or pinna. This distinction is the primary utility of Milian’s sign. * **Lymphangitis:** This refers to the inflammation of lymphatic channels, typically presenting as red, tender streaks extending proximally from a site of infection. * **Abscess:** This is a localized collection of pus within the dermis or deeper tissues, characterized by fluctuance, rather than the well-demarcated, "butterfly" distribution seen in facial erysipelas. **High-Yield Clinical Pearls for NEET-PG:** * **Erysipelas:** Characterized by a "Step-ladder" rise in temperature, a "Peau d'orange" appearance, and **sharply demarcated borders**. * **Common Site:** Lower limbs are most common; the face is the second most common. * **Treatment of Choice:** Penicillin (as it is primarily Streptococcal). * **Differential Diagnosis:** In Cellulitis, the borders are **ill-defined** and not raised, as the infection is deeper.

Q: A 35-year-old sailor presents with painful, flocculent masses in his groin. Physical examination reveals multiple enlarged, abscessed lymph nodes with draining indolent sinuses. The patient recalls a prior small papular lesion on his penis that resolved spontaneously. What is the most likely diagnosis?

Lymphogranuloma venereum. ### **Explanation** The clinical presentation is classic for **Lymphogranuloma venereum (LGV)**, caused by *Chlamydia trachomatis* serovars L1, L2, and L3 [1]. **1. Why the correct answer is right:** LGV typically progresses through three stages [1]. The patient’s history of a **painless, self-healing primary papule** (Stage 1) followed by the development of painful, fluctuant inguinal lymphadenopathy (Stage 2) is pathognomonic [1]. The "flocculent masses" and **draining indolent sinuses** represent ruptured "buboes." A key diagnostic feature often mentioned in exams is the **"Groove sign,"** where the inguinal ligament divides the matted lymph nodes [1]. **2. Why the incorrect options are wrong:** * **Condyloma acuminatum:** Caused by HPV 6 and 11; presents as painless, cauliflower-like warts, not abscessed lymph nodes [3]. * **Granuloma inguinale (Donovanosis):** Caused by *Klebsiella granulomatis*. It presents as **painless**, beefy-red ulcerative lesions that bleed on touch. It lacks true lymphadenopathy (presents with "pseudobuboes") [1]. * **Herpes virus infection (HSV-2):** Presents with multiple, painful, grouped vesicles on an erythematous base [2]. While it causes lymphadenopathy, it does not typically lead to fluctuant, draining buboes or indolent sinuses. **3. NEET-PG High-Yield Pearls:** * **Organism:** *Chlamydia trachomatis* (L1-L3). * **Drug of Choice:** Doxycycline (100 mg BID for 21 days). Erythromycin is the alternative for pregnant patients. * **Diagnostic Sign:** **Groove Sign of Greenblatt** (inguinal ligament indentation). * **Histology:** Stellated abscesses (star-shaped necrosis) within the lymph nodes [1]. * **Late Complication:** "Esthiomene" (chronic hypertrophic ulceration and edema of external genitalia) [1].

Q: Which drug is useful in Lepra reactions?

Clofazimine. **Explanation:** The correct answer is **Clofazimine**. **Why Clofazimine is correct:** Lepra reactions (Type 1 and Type 2/Erythema Nodosum Leprosum) are immunologically mediated inflammatory episodes occurring during the course of leprosy. While Clofazimine is primarily a bacteriostatic antileprotic drug, it possesses unique **anti-inflammatory and immunosuppressive properties**. It inhibits the release of lysosomal enzymes and interferes with neutrophil chemotaxis. This dual action makes it highly effective in managing and preventing Type 2 Lepra reactions (ENL), often reducing the requirement for corticosteroids. **Why other options are incorrect:** * **Penicillins:** These are beta-lactam antibiotics that inhibit cell wall synthesis. They have no activity against *Mycobacterium leprae* and no anti-inflammatory properties, making them irrelevant in leprosy management. * **Dapsone:** While a cornerstone of Multidrug Therapy (MDT) for leprosy, Dapsone is a common **trigger** for lepra reactions. It has no anti-inflammatory effect and must be continued during a reaction, but it does not treat it. * **Rifampicin:** This is the most potent bactericidal drug against *M. leprae*. However, its role is strictly antimicrobial (inhibiting DNA-dependent RNA polymerase). It does not possess anti-inflammatory properties and cannot manage the immunological flare-ups seen in lepra reactions. **High-Yield Clinical Pearls for NEET-PG:** * **Clofazimine Side Effects:** Causes brownish-black skin discoloration and ichthyosis (dry, scaly skin). It can also cause enteritis (reddish-brown discoloration of the gut mucosa). * **Drug of Choice for Type 2 Reaction (ENL):** **Thalidomide** is the drug of choice for severe ENL (except in women of childbearing age due to teratogenicity). **Corticosteroids** (Prednisolone) are the mainstay for Type 1 reactions. * **MDT Regimen:** Clofazimine is a component of the WHO MDT for Multibacillary (MB) leprosy.

Question 1

A 38-year-old man with a known history of well-controlled plaque psoriasis on his elbows and knees presents for a routine review. He mentions his nails have become unsightly and occasionally painful. Examination of the hands is performed and the findings are shown (Image 3). Which histopathological finding in the nail unit is most directly responsible for the proximal nail plate changes visible in this image?

Accepted Answer

B. Parakeratotic foci in the nail matrix with retention of nuclei in the keratogenous zone

Answer

A. Spongiosis of the nail matrix epithelium with exocytosis of lymphocytes

Answer

C. Subungual acantholysis with suprabasal cleft formation in the hyponychium

Answer

D. Interface vacuolar degeneration at the nail matrix basement membrane

Question 2

A patient presents with multiple hypopigmented and hypesthetic patches on the lateral aspect of the forearm, with abundant acid-fast bacilli (AFB) and granulomatous inflammation on histology. What is the most likely diagnosis?

Accepted Answer

Borderline leprosy

Answer

Tuberculoid leprosy

Answer

Intermediate leprosy

Answer

Lepromatous leprosy

Question 3

What is the worldwide accepted minimum dose of penicillin for latent syphilis?

Accepted Answer

7.0 million units

Answer

4.8 million units

Answer

6.0 million units

Answer

10 units

Question 4

Which subtype of leprosy has the maximum number of TH1 cells?

Accepted Answer

Tuberculoid (TT)

Answer

Bande (BB)

Answer

Lepromatous (LL)

Answer

Borderline leprosy

Question 5

A young boy has a single scaly, hypoanaesthetic patch over the hand plus thickened ulnar nerve. What is the diagnosis?

Accepted Answer

Tuberculoid leprosy

Answer

Lepromatous leprosy

Answer

Indeterminate leprosy

Answer

Borderline leprosy

Question 6

What is most important in establishing the diagnosis of leprosy?

Accepted Answer

Slit smear for AFB

Answer

Evidence of neural involvement

Answer

Hypopigmented patches

Answer

Positive lepromin test

Question 7

Milian's ear sign is seen in which of the following conditions?

Accepted Answer

Erysipelas

Answer

Cellulitis

Answer

Lymphangitis

Answer

Abscess

Question 8

Which of the following is true of lepromatous leprosy?

Accepted Answer

Involvement of earlobes

Answer

Bacterial index + to ++

Answer

Symmetrical involvement

Answer

Only a few bacilli are seen in the lesion

Question 9

A 35-year-old sailor presents with painful, flocculent masses in his groin. Physical examination reveals multiple enlarged, abscessed lymph nodes with draining indolent sinuses. The patient recalls a prior small papular lesion on his penis that resolved spontaneously. What is the most likely diagnosis?

Accepted Answer

Lymphogranuloma venereum

Answer

Condyloma acuminatum

Answer

Granuloma inguinale

Answer

Herpes virus infection

Question 10

Which drug is useful in Lepra reactions?

Accepted Answer

Clofazimine

Answer

Pencillins

Answer

Dapsone

Answer

Rifampicin

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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