Bacterial Skin Infections Practice Questions

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.

Q: Which of the following tuberculides is characterized by involvement of sweat glands and hair follicles with non-caseating epithelioid granuloma?

Lichen scrofulosorum. **Explanation:** **Lichen scrofulosorum** is a rare, asymptomatic, "id" reaction (tuberculide) occurring in individuals with high immunity against *Mycobacterium tuberculosis*. It typically presents as clusters of tiny, lichenoid, skin-colored to reddish-brown papules on the trunk. * **Histopathology:** The hallmark is the presence of **non-caseating epithelioid cell granulomas** specifically localized around **adnexal structures**, such as hair follicles and sweat glands (perifollicular or periadnexal distribution). This anatomical localization is the key diagnostic feature. **Analysis of Incorrect Options:** * **Miliary Tuberculosis:** This is a form of primary cutaneous TB (not a tuberculide) resulting from hematogenous spread. Histology shows multiple small areas of necrosis and numerous acid-fast bacilli (AFB), unlike the paucibacillary nature of tuberculides. * **Papulonecrotic Tuberculide:** Characterized by dusky red papules that undergo central **necrosis** and heal with varioliform scarring. Histology shows wedge-shaped necrosis and vasculitis, not periadnexal non-caseating granulomas. * **Lupus Vulgaris:** The most common form of chronic cutaneous TB. Histology shows typical **tubercles** (caseating granulomas) in the upper dermis with marked epidermal changes (atrophy or pseudoepitheliomatous hyperplasia). It is not specifically associated with sweat gland involvement. **High-Yield Clinical Pearls for NEET-PG:** * **Tuberculides** (Lichen scrofulosorum, Papulonecrotic tuberculide, Erythema induratum) are hypersensitivity reactions where AFB are **absent** in lesions, but the Mantoux test is strongly positive. * Lichen scrofulosorum is most commonly seen in **children and adolescents** with systemic TB (usually nodal or skeletal). * **Treatment:** It responds rapidly to standard Anti-Tubercular Therapy (ATT).

Q: Which of the following conditions does not involve nerve damage?

Indeterminate leprosy. In leprosy (Hansen’s disease), the degree of nerve involvement is dictated by the host's cell-mediated immunity (CMI). **Why Indeterminate Leprosy is the correct answer:** Indeterminate leprosy is the **earliest clinical stage** of the disease. It typically presents as a single, ill-defined, hypopigmented macule with preserved or only slightly impaired sensation. At this stage, the disease has not yet polarized into the Ridley-Jopling spectrum. Crucially, there is **no peripheral nerve trunk enlargement or damage** at this stage. It may either resolve spontaneously or progress to other forms depending on the patient's immune response. **Why the other options are incorrect:** * **Tuberculoid Leprosy (TT):** Characterized by a strong CMI response. This leads to intense inflammation and granuloma formation within nerves, causing **early, severe, and asymmetrical** nerve damage and enlargement. * **Lepromatous Leprosy (LL):** Characterized by low CMI and high bacillary load. Nerve involvement is **late, symmetrical, and progressive**, involving small dermal nerve twigs first and then major trunks. * **Borderline Tuberculoid (BT):** This is the most common clinical presentation. It involves significant nerve damage, often presenting with multiple enlarged nerves and a high risk of "reversal reactions" which further exacerbate nerve palsy. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest sensation lost:** Temperature (Cold followed by Hot), then Touch, then Pain, and lastly Deep Pressure. * **Most commonly involved nerve:** Ulnar nerve (leads to claw hand). * **Cardinal signs of Leprosy:** Hypopigmented patches with loss of sensation, thickened peripheral nerves, and a positive skin smear for *M. leprae*. * **Indeterminate Leprosy Histology:** Shows non-specific lymphocytic infiltration around skin appendages and neurovascular bundles; Acid-Fast Bacilli (AFB) are usually very difficult to find.

Q: True about Lucio's phenomenon is:

Ischemic necrosis. **Explanation:** **Lucio’s Phenomenon** is a rare, severe variant of Type 2 Lepra reaction specifically associated with **Diffuse Lepromatous Leprosy (of Lucio and Latapi)**. **Why Option C is Correct:** The underlying pathophysiology involves a massive invasion of the vascular endothelium by *Mycobacterium leprae*. This leads to **endothelial proliferation, necrotizing vasculitis, and thrombo-occlusion** of the dermal vessels. The resulting lack of blood supply causes **ischemic necrosis** of the skin, clinically manifesting as painful, jagged, purpuric macules that progress to necrotic ulcers (predominantly on the extremities). **Analysis of Incorrect Options:** * **Option A:** It is never seen in tuberculoid leprosy; it occurs exclusively in untreated, non-nodular diffuse lepromatous leprosy. * **Option B:** Unlike Erythema Nodosum Leprosum (ENL), which often occurs *after* starting Multi-Drug Therapy (MDT), Lucio’s phenomenon typically occurs in **untreated patients**. * **Option D:** While some classifications consider it a variant of Type 2 reaction, it is distinct from the classic Type 2 reaction (ENL). ENL is a Type III hypersensitivity (immune-complex mediated), whereas Lucio’s phenomenon is primarily a **thrombotic vasculopathy**. **High-Yield Clinical Pearls for NEET-PG:** * **Geographic distribution:** Most common in Mexico and Central America. * **Clinical sign:** Characterized by "Lucio’s leprosy" (diffuse infiltration of skin, loss of eyebrows/eyelashes, but no nodules). * **Histopathology:** Shows acid-fast bacilli (AFB) within the endothelial cells and thrombus formation. * **Treatment:** Standard MDT for Leprosy; systemic steroids have limited efficacy compared to their role in ENL.

Q: Tuberculides are seen in which of the following conditions?

Lichen scrofulosorum. **Explanation:** **Tuberculides** are a group of skin eruptions that represent a hypersensitivity reaction to a distant, often occult, focus of *Mycobacterium tuberculosis* in a patient with high immunity. Unlike true cutaneous tuberculosis, tuberculides are characterized by the **absence** of bacilli in the skin lesions (paucibacillary/sterile) and a strongly positive Mantoux test. **Why Option C is Correct:** **Lichen scrofulosorum** is a classic example of a tuberculide. It typically presents in children and young adults as asymptomatic, skin-colored to reddish-brown, follicular papules grouped in discoid patterns on the trunk. It occurs in individuals with high cell-mediated immunity and usually responds rapidly to anti-tubercular therapy (ATT). **Analysis of Incorrect Options:** * **Lupus vulgaris (A) and Scrofuloderma (B):** These are forms of **True Cutaneous Tuberculosis**. In these conditions, the bacteria are physically present in the skin lesions (though they may be paucibacillary in Lupus Vulgaris). * **Erythema nodosum (D):** While it can be a manifestation of tuberculosis, it is a non-specific reactive septal panniculitis seen in various conditions (Sarcoidosis, Leprosy, Streptococcal infections). It is not classified as a "tuberculide" in the strict dermatological sense. **High-Yield Clinical Pearls for NEET-PG:** * **Classification of Tuberculides:** 1. **Lichen scrofulosorum:** Follicular papules (most common in children). 2. **Papulonecrotic tuberculide:** Symmetrical dusky-red papules with central necrosis, usually on extensors. 3. **Erythema induratum of Bazin:** Nodular lesions on the calves (posterior leg), often ulcerating. * **Key Differentiator:** True cutaneous TB (e.g., Lupus Vulgaris) has a positive culture/PCR from the lesion; Tuberculides have a negative culture but a strongly positive Mantoux test.

Q: Multidrug therapy is indicated for which of the following conditions?

Leprosy. **Explanation:** **Multidrug Therapy (MDT)** is the cornerstone of treatment for **Leprosy** (Hansen’s Disease). The primary medical rationale for using MDT is to **prevent the emergence of drug resistance** in *Mycobacterium leprae*, particularly against Rifampicin. MDT also ensures a rapid clinical cure and reduces the duration of treatment. According to WHO guidelines, the regimen typically includes a combination of **Rifampicin, Dapsone, and Clofazimine** (for Multibacillary cases). **Analysis of Incorrect Options:** * **Syphilis:** Caused by *Treponema pallidum*, it is treated with **monotherapy**, specifically Benzathine Penicillin G (the drug of choice). Resistance to penicillin has not yet been documented in syphilis. * **Dermatitis Herpetiformis:** This is an autoimmune blistering disorder associated with gluten-sensitive enteropathy. The primary treatment is a **Gluten-Free Diet** and **Dapsone** (monotherapy) to control skin lesions. * **Ichthyosis Vulgaris:** This is a genetic keratinization disorder (Filaggrin mutation). It is managed with **topical emollients** and keratolytics (e.g., urea, lactic acid), not systemic antimicrobial therapy. **High-Yield Clinical Pearls for NEET-PG:** * **Paucibacillary (PB) Leprosy:** Treated for 6 months with Rifampicin and Dapsone. * **Multibacillary (MB) Leprosy:** Treated for 12 months with Rifampicin, Dapsone, and Clofazimine. * **Rifampicin** is the most bactericidal drug in the regimen and is administered once monthly under supervision. * **Clofazimine** is known for causing brownish-black skin discoloration and ichthyosis as side effects.

Q: Which of the following can lead to infiltration of ear lobules, loss of nails, and resorption of distal phalanges?

Lepromatous leprosy. **Explanation:** The correct answer is **Lepromatous Leprosy (LL)**. This clinical presentation is characteristic of the multibacillary end of the leprosy spectrum, where there is a high bacterial load due to deficient cell-mediated immunity (CMI). 1. **Why Lepromatous Leprosy is correct:** * **Infiltration of Ear Lobules:** In LL, *M. leprae* proliferates extensively in cooler areas of the body. Diffuse infiltration leads to thickening of the ear lobules (a classic early sign) and may eventually progress to "Leonine facies." * **Resorption of Distal Phalanges:** This occurs due to a combination of specific lepromatous osteitis, secondary pyogenic osteomyelitis (from neglected trauma to anesthetic limbs), and neurotrophic changes. * **Loss of Nails:** Chronic trophic changes and destruction of the nail matrix due to vascular compromise and repeated trauma lead to onychoatrophy or total nail loss. 2. **Why other options are incorrect:** * **Tuberculoid Leprosy (TT):** Characterized by strong CMI, few lesions (1-3), and early, severe nerve involvement. While it causes localized anesthesia, it does not typically present with diffuse infiltration of ear lobules or generalized resorption of phalanges. * **Indeterminate Leprosy:** This is the early, transitory stage of the disease. It presents as a single, ill-defined macule with slight sensory loss and never exhibits the chronic destructive features mentioned. **High-Yield Clinical Pearls for NEET-PG:** * **Ear Lobule:** The ear lobule is the site of choice for a slit-skin smear (SSS) because of its high bacterial density. * **Leonine Facies:** Caused by diffuse infiltration of the forehead, cheeks, and nose, along with **Madarosis** (loss of lateral 1/3rd of eyebrows). * **Internal Involvement:** LL is a systemic disease; it can involve the testes (leading to gynecomastia/sterility), the nasal septum (leading to saddle nose deformity), and the eyes.

Question 1

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 2

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

Question 3

A child presents with a facial lesion, as depicted in the accompanying image. A biopsy of the lesion is also shown. What is the most probable diagnosis?

Accepted Answer

Indeterminate leprosy

Answer

Lepromatous Leprosy

Answer

Pityriasis Rosea

Answer

Pityriasis alba

Question 4

Which of the following tuberculides is characterized by involvement of sweat glands and hair follicles with non-caseating epithelioid granuloma?

Accepted Answer

Lichen scrofulosorum

Answer

Miliary tuberculosis

Answer

Papulonecrotic tuberculide

Answer

Lupus vulgaris

Question 5

Which of the following conditions does not involve nerve damage?

Accepted Answer

Indeterminate leprosy

Answer

Tuberculoid leprosy

Answer

Lepromatous leprosy

Answer

Borderline tuberculoid leprosy

Question 6

True about Lucio's phenomenon is:

Accepted Answer

Ischemic necrosis

Answer

Associated with tuberculoid leprosy

Answer

Occurs as a side effect of treatment of leprosy

Answer

Also known as type 2 Lepra reaction

Question 7

Tuberculides are seen in which of the following conditions?

Accepted Answer

Lichen scrofulosorum

Answer

Lupus vulgaris

Answer

Scrofuloderma

Answer

Erythema nodosum

Question 8

Multidrug therapy is indicated for which of the following conditions?

Accepted Answer

Leprosy

Answer

Syphilis

Answer

Herpetiformis

Answer

Ichthyosis Vulgaris

Question 9

What is the treatment for Lucio phenomenon?

Accepted Answer

Exchange transfusion

Answer

Steroids

Answer

Lenalidomide

Answer

Clofazimine

Question 10

Which of the following can lead to infiltration of ear lobules, loss of nails, and resorption of distal phalanges?

Accepted Answer

Lepromatous leprosy

Answer

Tuberculoid leprosy

Answer

Indeterminate leprosy

Answer

Any of the above

Bacterial Skin Infections — MCQs

Bacterial Skin Infections — MCQs

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