Bacterial Skin Infections Practice Questions

Q: Which of the following statements are true about cellulitis of the lower limb?

External wound is always present. **Explanation:** Cellulitis is an acute inflammatory condition of the **deep dermis and subcutaneous tissue**, most commonly caused by *Streptococcus pyogenes* or *Staphylococcus aureus*. **Why Option D is the "Correct" Answer (Contextual Analysis):** In the context of clinical examinations like NEET-PG, the presence of a **portal of entry** (external wound, fissure, or tinea pedis) is considered a hallmark of cellulitis. While "always" is a strong word in medicine, the pathogenesis typically requires a breach in the skin barrier to allow bacteria to invade the deeper layers. **Analysis of Other Options:** * **Option A (Infection of skin and subcutaneous tissue):** This is a **true** statement. Cellulitis involves the deep dermis and subcutaneous fat. (Note: In many standard textbooks, A and B are also technically correct; however, if the question asks for the most definitive clinical requirement for its onset, the portal of entry is emphasized). * **Option B (Fever and malaise are common):** This is **true**. Systemic symptoms are frequent due to the inflammatory nature of the infection. * **Option C (Margins are distinct):** This is **false**. Cellulitis is characterized by **ill-defined, diffuse margins**. Distinct, well-demarcated, and raised margins are the classic feature of **Erysipelas** (a more superficial infection). **High-Yield Clinical Pearls for NEET-PG:** 1. **Erysipelas vs. Cellulitis:** Erysipelas involves the upper dermis and superficial lymphatics (distinct borders); Cellulitis involves deeper layers (indistinct borders). 2. **Commonest Site:** Lower limbs. 3. **Risk Factors:** Lymphedema (most common), obesity, and tinea pedis (athlete's foot). 4. **Milian’s Ear Sign:** Erysipelas can involve the pinna (which lacks subcutaneous tissue), whereas cellulitis cannot. 5. **Treatment:** Systemic antibiotics (e.g., Cloxacillin or Cephalosporins).

Q: A patient presents with two ulcers on the chest wall and axilla, associated with underlying sinus tracts and discharge. What is the most likely diagnosis?

Scrofuloderma. **Explanation:** The clinical presentation of ulcers associated with **underlying sinus tracts and discharge** is the hallmark of **Scrofuloderma** (Colliquative Tuberculosis). **1. Why Scrofuloderma is correct:** Scrofuloderma occurs due to the **direct extension** of tuberculosis from an underlying infected structure, most commonly a lymph node (cervical or axillary) or a bone/joint. It begins as a painless, firm subcutaneous nodule that eventually breaks down to form an ulcer with undermined edges, connected by discharging sinus tracts. The chest wall and axilla are classic sites due to the proximity of lymph node chains. **2. Why other options are incorrect:** * **Lupus Vulgaris:** This is the most common form of cutaneous TB in adults. It typically presents as an **"apple-jelly" nodule** on diascopy. It is characterized by plaques that show peripheral expansion and central scarring, not sinus tracts. * **Lichen Scrofulosorum:** This is a **tuberculid** (hypersensitivity) reaction. It presents as asymptomatic, skin-colored, follicular papules, usually on the trunk of children. It does not ulcerate or form sinuses. * **Tuberculosis Verrucosa Cutis (TVC):** Also known as "Prosector’s wart," this occurs due to **exogenous inoculation** in a previously sensitized individual. It presents as a solitary, warty (verrucous) plaque, typically on the hands or feet. **Clinical Pearls for NEET-PG:** * **Most common cutaneous TB in India:** Lupus Vulgaris. * **Most common cutaneous TB in children:** Scrofuloderma. * **Multibacillary forms:** Scrofuloderma and TB Cutis Orificialis (high bacterial load). * **Paucibacillary forms:** Lupus Vulgaris and TVC (low bacterial load). * **Key Histology:** Tuberculoid granulomas with or without caseation necrosis.

Q: Apple jelly nodules are seen in which condition?

Lupus vulgaris. **Explanation:** **Lupus Vulgaris (Correct Answer):** Lupus vulgaris is the most common form of chronic, progressive **paucibacillary cutaneous tuberculosis**. It occurs in individuals with a high degree of cell-mediated immunity. The characteristic clinical finding is a plaque composed of soft, reddish-brown papules. When **diascopy** (pressing a glass slide against the lesion) is performed, the vascular blanching reveals yellowish-brown, translucent spots resembling **"apple jelly nodules."** This appearance is due to the underlying granulomatous infiltrate in the dermis. **Analysis of Incorrect Options:** * **Cutaneous Anaphylaxis:** This refers to immediate hypersensitivity reactions (Type I) characterized by wheals, flare, and edema (urticaria), not granulomatous nodules. * **Erythroderma:** Also known as "Exfoliative Dermatitis," this is a clinical state where >90% of the body surface is erythematous and scaling. It is a reaction pattern, not a specific nodular infection. * **Erysipelas:** This is a superficial bacterial infection (usually *S. pyogenes*) characterized by a well-demarcated, "fiery red" erythematous plaque with a raised border. It lacks the granulomatous "apple jelly" feature. **High-Yield Clinical Pearls for NEET-PG:** * **Diascopy:** Used to differentiate purpura (non-blanching) from erythema (blanching) and to reveal apple jelly nodules in granulomatous diseases. * **Other conditions with Apple Jelly Nodules:** While classic for Lupus Vulgaris, they can also be seen in **Sarcoidosis** and **Leishmaniasis**. * **Lupus Vulgaris Complication:** The most dreaded long-term complication is the development of **Squamous Cell Carcinoma (Marjolin’s ulcer)** within the scar.

Q: Which of the following lesions is NOT seen in leprosy?

Vesicles. **Explanation:** Leprosy (Hansen’s Disease), caused by *Mycobacterium leprae*, primarily affects the skin and peripheral nerves. The hallmark of the disease is the presence of skin lesions associated with **sensory loss** and **nerve thickening**. **Why Vesicles are NOT seen:** Vesicles (small fluid-filled blisters) are characteristic of acute inflammatory conditions, viral infections (like Herpes), or allergic contact dermatitis. Leprosy is a **chronic granulomatous inflammation**. The pathology involves the infiltration of the dermis by lymphocytes and histiocytes (forming granulomas), which leads to solid elevations or pigmentary changes, but **never** to the intraepidermal or subepidermal fluid accumulation required to form vesicles. **Analysis of other options:** * **Erythematous macules:** Commonly seen in Tuberculoid (TT) and Borderline Tuberculoid (BT) leprosy due to the host's immune response. * **Hypopigmented patches:** The most common presentation in early (Indeterminate) leprosy and Tuberculoid types. The loss of pigment occurs due to the destruction of melanocytes or interference with melanin transfer. * **Flat and raised patches:** Leprosy presents a wide spectrum of morphology; flat patches are seen in early stages, while raised patches (plaques) with well-defined borders are classic features of Tuberculoid leprosy. **High-Yield Clinical Pearls for NEET-PG:** * **Cardinal Signs:** Hypopigmented/erythematous patches with loss of sensation, thickened nerves, and a positive slit-skin smear. * **The "Immune" Zones:** Leprosy typically spares the warmer areas of the body, such as the axilla, groin, and the midline of the back (due to *M. leprae's* preference for cooler temperatures). * **Lucio Phenomenon:** A rare, severe necrotizing vasculitis seen in diffuse lepromatous leprosy where **bullae and ulcers** may occur, but these are secondary to infarcts, not a primary feature of leprosy itself.

Q: Which of the following is NOT a deformity associated with Leprosy?

Clutton's joint. **Explanation:** The correct answer is **Clutton’s joint** because it is a manifestation of **Late Congenital Syphilis**, not Leprosy. It is characterized by symmetrical, painless hydrarthrosis (swelling) of the knees, typically occurring between the ages of 8 and 15 years. **Why the other options are associated with Leprosy:** Leprosy (Hansen’s disease) is a chronic infectious disease that primarily affects the peripheral nerves, leading to characteristic motor deformities: * **Claw hand:** Caused by involvement of the **Ulnar nerve** (most common) and sometimes the Median nerve, leading to paralysis of the intrinsic muscles of the hand. * **Lagophthalmos:** Results from damage to the **Zygomatic branch of the Facial nerve**, leading to the inability to close the eyelid completely, which risks corneal ulceration. * **Foot drop:** Caused by involvement of the **Common Peroneal nerve**, leading to paralysis of the dorsiflexors of the foot. **High-Yield Clinical Pearls for NEET-PG:** * **Most common nerve involved in Leprosy:** Ulnar nerve. * **Most common nerve involved in the lower limb:** Common Peroneal nerve. * **Hutchinson’s Triad (Congenital Syphilis):** Interstitial keratitis, Hutchinson’s teeth (notched incisors), and Sensorineural deafness. * **Face of Leprosy:** "Leonine facies" (due to infiltration of skin) and "Madarosis" (loss of lateral eyebrows). * **Treatment:** WHO MDT (Rifampicin, Dapsone, and Clofazimine).

Q: All are the characteristics of cellulitis, EXCEPT?

Well circumscribed. **Explanation:** Cellulitis is an acute inflammatory condition of the **deep dermis and subcutaneous tissue**, most commonly caused by *Streptococcus pyogenes* (Group A Strep) or *Staphylococcus aureus*. **Why "Well circumscribed" is the correct answer:** Unlike Erysipelas, which involves the superficial dermis and lymphatics and presents with sharply demarcated borders, **Cellulitis has ill-defined, diffuse, and non-palpable borders.** This is because the infection occurs deeper in the tissue, allowing the inflammation to spread laterally without a clear anatomical barrier. **Analysis of other options:** * **Acute onset:** Cellulitis typically presents rapidly with the "cardinal signs of inflammation": rubor (redness), calor (warmth), dolor (pain), and tumor (swelling). * **Doughy to indurated consistency:** The affected area feels firm (indurated) or "doughy" due to significant inflammatory edema within the subcutaneous layers. * **Caused by aerobic bacteria:** The majority of cases are caused by aerobic Gram-positive cocci (*S. pyogenes* and *S. aureus*). Anaerobic bacteria are usually only implicated in specific scenarios like diabetic foot ulcers or human bites. **NEET-PG High-Yield Pearls:** 1. **Erysipelas vs. Cellulitis:** Erysipelas is superficial, has **raised, well-defined borders**, and often involves the "Milian’s ear sign" (as the ear lacks subcutaneous tissue, only erysipelas can affect it). 2. **Portal of entry:** Always look for a break in the skin (tinea pedis, trauma, or ulcer) as the inciting factor. 3. **Treatment:** Systemic antibiotics (e.g., Cloxacillin or Cephalexin) are the mainstay. If MRSA is suspected, Vancomycin or Linezolid is used.

Question 1

Which of the following statements are true about cellulitis of the lower limb?

Accepted Answer

External wound is always present

Answer

Infection of skin and subcutaneous tissue

Answer

Fever and malaise are common

Answer

Margins are distinct

Question 2

A patient presents with two ulcers on the chest wall and axilla, associated with underlying sinus tracts and discharge. What is the most likely diagnosis?

Accepted Answer

Scrofuloderma

Answer

Lupus vulgaris

Answer

Lichen scrofulosorum

Answer

Tuberculous verrucous cutis

Question 3

Apple jelly nodules are seen in which condition?

Accepted Answer

Lupus vulgaris

Answer

Cutaneous anaphylaxis

Answer

Erythroderma

Answer

Erysipelas

Question 4

Which of the following lesions is NOT seen in leprosy?

Accepted Answer

Vesicles

Answer

Erythematous macule

Answer

Hypopigmented patch

Answer

Flat and raised patches

Question 5

Skin biopsy in leprosy is characterized by which of the following?

Accepted Answer

All of the above

Answer

Periappendageal bacilli

Answer

Periappendageal lymphocytosis

Answer

Perivascular lymphocytosis

Question 6

Which of the following conditions can be caused by Staphylococcus?

Accepted Answer

Impetigo contagiosa

Answer

Ecthyma

Answer

Erythrasma

Answer

Furuncle

Question 7

Which of the following is NOT a deformity associated with Leprosy?

Accepted Answer

Clutton's joint

Answer

Claw hand

Answer

Lagophthalmos

Answer

Foot drop

Question 8

What is the recommended treatment for granuloma inguinale?

Accepted Answer

Tetracycline

Answer

Sulphanomide

Answer

Streptomycin

Answer

Penicillin

Question 9

All are the characteristics of cellulitis, EXCEPT?

Accepted Answer

Well circumscribed

Answer

Acute onset

Answer

Doughy to indurated consistency

Answer

Caused by aerobic bacteria

Question 10

The Ridley-Jopling classification for leprosy is based on which of the following parameters?

Accepted Answer

Clinical, bacteriological, immunological

Answer

Histopathological, clinical, therapeutic

Answer

Histopathological, epidemiological, therapeutics

Answer

Histopathological, clinical, epidemiological

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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