Tropical Dermatology — MCQs

Tropical Dermatology Indian Medical PG Practice Questions and MCQs

Question 21: Veldt sore is most common in which of the following conditions or environments?

A. Hilly areas
B. Tropical climate
C. Rainy areas
D. Deserts (Correct Answer)

Explanation: **Explanation:** **Veldt sore**, also known as **Desert sore** or **Barcoo rot**, is a cutaneous manifestation of **Corynebacterium diphtheriae** (non-toxigenic strains). It is characterized by chronic, punched-out ulcers, typically occurring on exposed areas like the hands, forearms, and shins. 1. **Why Deserts (Option D) is correct:** The condition is classically associated with hot, arid, and desert environments. The underlying medical concept involves a combination of factors: minor trauma (abrasions/insect bites) acting as a portal of entry, coupled with poor hygiene and intense solar radiation which delays wound healing. It was historically significant among soldiers serving in desert campaigns (e.g., North Africa during WWII). 2. **Why other options are incorrect:** * **Hilly areas (A):** While trauma can occur here, the specific bacterial colonization and environmental stressors (dry heat) required for Veldt sore are absent. * **Tropical/Rainy areas (B & C):** These environments are more commonly associated with fungal infections (Tinea), Leishmaniasis, or tropical ulcers caused by *Fusobacterium* and *Borrelia*. Veldt sore specifically requires the dry, dusty conditions of the desert. **Clinical Pearls for NEET-PG:** * **Causative Agent:** *Corynebacterium diphtheriae* (most common) or *Staphylococcus aureus*. * **Clinical Morphology:** A painful vesicle that ruptures to form a **punched-out ulcer** with a grayish-green base and undermined edges. * **Differential Diagnosis:** Cutaneous Leishmaniasis (Oriental Sore), which also occurs in deserts but is caused by a protozoan and has a longer incubation period. * **Treatment:** Local wound care and systemic penicillin or erythromycin.

Question 22: What is the recommended treatment for severe ulnar neuritis in borderline tuberculoid leprosy?

A. MDT only
B. MDT + steroid (Correct Answer)
C. Wait and watch
D. MDT + thalidomide

Explanation: **Explanation:** In leprosy, nerve involvement is the primary cause of morbidity. **Ulnar neuritis** in Borderline Tuberculoid (BT) leprosy is typically a manifestation of a **Type 1 Lepra Reaction** (Reversal Reaction). This is a delayed hypersensitivity (Type IV) response where an increase in cell-mediated immunity leads to acute inflammation of the nerves. 1. **Why MDT + Steroids is correct:** While Multi-Drug Therapy (MDT) treats the *Mycobacterium leprae* infection, it does not stop the immunological damage to the nerve. **Systemic corticosteroids** (e.g., Prednisolone) are the gold standard for treating acute neuritis. They reduce endoneural edema and suppress the inflammatory cascade, preventing permanent nerve damage and subsequent physical disability (e.g., claw hand). 2. **Why other options are wrong:** * **MDT only:** MDT kills the bacilli but cannot control the acute immunological reaction. Relying on MDT alone during active neuritis leads to irreversible nerve fibrosis. * **Wait and watch:** Neuritis is a medical emergency in dermatology. Delaying treatment leads to permanent motor and sensory loss. * **MDT + Thalidomide:** Thalidomide is the drug of choice for **Type 2 Lepra Reaction** (Erythema Nodosum Leprosum), which occurs in lepromatous poles. It is ineffective in Type 1 reactions. **High-Yield Clinical Pearls for NEET-PG:** * **Steroid Regimen:** Usually started at 40mg/day (or 1mg/kg) and tapered over 12–24 weeks. * **Silent Neuritis:** Nerve damage occurring without pain or tenderness; it also requires urgent steroid therapy. * **Type 1 Reaction:** Common in BT, BB, and BL leprosy; characterized by "upgrading" of lesions (erythema/edema) and neuritis. * **Ulnar Nerve:** The most common peripheral nerve involved in leprosy.

Question 23: What is the main cytokine involved in the erythema nodosum leprosum reaction?

A. Interleukin 2
B. Interferon gamma
C. Tumour necrosis factor alpha (Correct Answer)
D. Macrophage colony stimulating factor

Explanation: **Explanation:** **Erythema Nodosum Leprosum (ENL)**, also known as a **Type 2 Lepra Reaction**, is a systemic immune-complex-mediated (Gell and Coombs Type III) hypersensitivity reaction occurring primarily in patients with lepromatous (LL) or borderline lepromatous (BL) leprosy. 1. **Why TNF-α is correct:** **Tumour Necrosis Factor-alpha (TNF-α)** is the central mediator in the pathogenesis of ENL. During the reaction, there is a massive release of TNF-α from activated macrophages and monocytes in response to the breakdown of *Mycobacterium leprae*. High serum levels of TNF-α correlate with the clinical severity of the reaction (fever, painful subcutaneous nodules, and neuritis). This is clinically significant because **Thalidomide**, the drug of choice for severe ENL, works primarily by inhibiting TNF-α synthesis. 2. **Why other options are incorrect:** * **Interleukin-2 (IL-2) and Interferon-gamma (IFN-γ):** These are Th1-type cytokines. They are the hallmark of **Type 1 Lepra Reactions** (Reversal Reactions), which involve a shift toward cell-mediated immunity. In ENL, the cytokine profile is predominantly Th2-driven, though TNF-α remains the primary effector. * **Macrophage colony-stimulating factor (M-CSF):** While involved in general macrophage differentiation, it is not a specific or primary mediator of the acute inflammatory cascade seen in ENL. **High-Yield Clinical Pearls for NEET-PG:** * **Mechanism:** Type III Hypersensitivity (Immune complex deposition). * **Clinical Features:** Tender evanescent nodules, high-grade fever, arthralgia, and iridocyclitis. * **Drug of Choice:** **Thalidomide** (specifically for ENL, not Type 1). * **Alternative Treatment:** Clofazimine (high dose) or systemic corticosteroids. * **Histopathology:** Shows **leucocytoclastic vasculitis** superimposed on lepromatous features.

Question 24: A saucer-shaped lesion is found in which type of leprosy?

A. Lepromatous leprosy
B. Tuberculoid leprosy
C. Borderline leprosy (Correct Answer)
D. Indeterminate leprosy

Explanation: **Explanation:** The **saucer-shaped lesion** (also known as the "inverted saucer" appearance) is a classic morphological hallmark of **Borderline Tuberculoid (BT)** or **Borderline Borderline (BB)** leprosy. This appearance is characterized by a lesion with a well-defined, raised, and erythematous outer edge that slopes gradually toward a flattened, pale, or hypopigmented center. **Why Borderline Leprosy is correct:** In the Ridley-Jopling classification, borderline cases represent an unstable immunological state. The "saucer" morphology occurs because the body attempts to contain the infection (leading to the raised, active border) but fails to do so completely, resulting in a large, asymmetrical lesion with central clearing or flattening. **Analysis of Incorrect Options:** * **Lepromatous Leprosy (LL):** Presents with multiple, symmetrical, small macules, papules, or nodules (lepromas). The lesions have vague borders and do not show the characteristic saucer shape. * **Tuberculoid Leprosy (TT):** Typically presents as a single (or very few), well-defined, anesthetic, hairless plaque. While the margins are sharp, they do not typically exhibit the specific "sloping" saucer morphology seen in borderline types. * **Indeterminate Leprosy:** This is the earliest stage, presenting as a single, ill-defined hypopigmented macule with vague borders and no significant sensory loss. **High-Yield Clinical Pearls for NEET-PG:** * **Swiss-Cheese Appearance:** Characteristic of **Borderline Borderline (BB)** leprosy, where "punched-out" clear areas appear within a large plaque. * **Leonine Facies:** Seen in **Lepromatous Leprosy (LL)** due to diffuse infiltration of the face. * **Nerve Involvement:** Nerve thickening is most asymmetrical in BT leprosy but most extensive/symmetrical in LL. * **Madarosis:** Loss of the lateral one-third of eyebrows, a classic sign of LL.

Question 25: What type of reaction is seen in Type I Leprosy reaction?

A. Type I
B. Type II
C. Type III
D. Type IV (Correct Answer)

Explanation: **Explanation:** Leprosy reactions are acute inflammatory episodes occurring during the chronic course of the disease. Understanding the underlying immunology is crucial for NEET-PG. **Why Type IV is Correct:** Type I Leprosy Reaction (also known as **Reversal Reaction**) is a **Type IV Hypersensitivity reaction** (Delayed-type hypersensitivity). It occurs due to a sudden increase in cell-mediated immunity (CMI) against *Mycobacterium leprae* antigens. This typically occurs in unstable borderline cases (BT, BB, and BL). Clinically, it manifests as sudden redness and edema of existing skin lesions and acute neuritis (nerve pain and tenderness). **Why other options are incorrect:** * **Type I (IgE-mediated):** This involves immediate hypersensitivity (e.g., anaphylaxis, urticaria), which plays no role in leprosy reactions. * **Type II (Antibody-mediated):** This involves cytotoxic antibodies (e.g., autoimmune hemolytic anemia), not seen in leprosy. * **Type III (Immune-complex mediated):** This is the mechanism for **Type II Leprosy Reaction** (Erythema Nodosum Leprosum or ENL). In ENL, antigen-antibody complexes deposit in tissues, causing systemic symptoms like fever and painful evanescent nodules. **High-Yield Clinical Pearls for NEET-PG:** * **Type I Reaction:** Seen in Borderline leprosy; treated primarily with **Corticosteroids**. It is "Reversal" because the patient moves toward the Tuberculoid pole (upgrading). * **Type II Reaction (ENL):** Seen in LL and BL cases; **Thalidomide** is the drug of choice (except in women of childbearing age). * **Lucio Phenomenon:** A rare, severe Type III reaction seen in diffuse lepromatous leprosy, characterized by necrotizing vasculitis.

Question 26: Type 1 lepra reaction is treated with?

A. Corticosteroid (Correct Answer)
B. Minocycline
C. Dapsone
D. Rifampicin

Explanation: **Explanation:** **Type 1 Lepra Reaction (Reversal Reaction)** is a Delayed Hypersensitivity (Type IV) reaction occurring in borderline cases of leprosy (BT, BB, BL). It is characterized by acute inflammation of existing skin lesions and, more critically, **acute neuritis**. 1. **Why Corticosteroids are the Correct Answer:** The primary goal in managing Type 1 reactions is to suppress the cell-mediated immune response to prevent irreversible nerve damage and physical deformity. **Systemic Corticosteroids (Prednisolone)** are the gold standard treatment. They act rapidly to reduce edema and inflammation within the nerve sheath, thereby preventing permanent axonal loss. The typical regimen involves a tapering dose of Prednisolone over 3–6 months. 2. **Why Other Options are Incorrect:** * **Minocycline, Dapsone, and Rifampicin:** These are bactericidal/bacteriostatic antibiotics used in **Multi-Drug Therapy (MDT)** to kill *Mycobacterium leprae*. While MDT should be continued during a reaction, these drugs do not treat the immunological flare itself. In fact, starting MDT can sometimes trigger a Type 1 reaction by releasing bacterial antigens. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice for Type 2 Reaction (ENL):** Thalidomide (for severe/recurrent cases) or Corticosteroids. * **Key Clinical Sign:** Sudden redness/swelling of old lesions + new onset nerve tenderness/loss of function. * **Management Tip:** Never stop MDT during a lepra reaction. * **Clofazimine:** While primarily an antileprotic, it has anti-inflammatory properties and is used as a steroid-sparing agent in Type 2 reactions, but it is less effective for the acute phase of Type 1 reactions.

Question 27: Ainhum is typically seen at which anatomical location?

A. Base of the great toe
B. Fingertips
C. Base of the toes (Correct Answer)
D. Ankle

Explanation: **Explanation:** **Ainhum** (also known as *Dactylolysis Spontanea*) is a rare clinical condition characterized by the formation of a tight, constricting fibrous band around the digit. **Why the correct answer is right:** The condition typically occurs at the **base of the toes**, most commonly involving the **fifth (little) toe**. The constriction begins in the digito-plantar fold and progresses circumferentially. Over time, this fibrous band leads to progressive ischemia, bone resorption (rarefaction), and eventual spontaneous auto-amputation of the digit. It is most frequently seen in individuals of African descent living in tropical climates. **Why the incorrect options are wrong:** * **Base of the great toe:** While Ainhum affects the toes, it almost exclusively targets the fifth toe; the great toe is rarely, if ever, the primary site. * **Fingertips:** Ainhum is a disease of the lower extremities. Constrictions on the fingers are usually associated with "Pseudo-ainhum," which is secondary to other conditions like leprosy, scleroderma, or Vohwinkel syndrome. * **Ankle:** Ainhum is a digital pathology. Constrictions at the ankle are not a feature of this condition. **NEET-PG High-Yield Pearls:** * **Pseudo-ainhum:** Unlike true Ainhum, this is secondary to systemic diseases (e.g., Psoriasis, Diabetes, Leprosy) or congenital bands (Streeter’s dysplasia). * **Radiological Sign:** The "hook-like" appearance of the distal phalanx or narrowing of the shaft of the phalanx is characteristic. * **Staging:** It follows four clinical stages, ending in auto-amputation. * **Treatment:** Early stages may be treated with Z-plasty; late stages require surgical amputation if auto-amputation is painful.

Question 28: What is the characteristic feature of borderline leprosy?

A. Inverted saucer lesion (Correct Answer)
B. Erythema nodosum leprosum (ENL)
C. Hypopigmented macules and plaques all over the body
D. Glove and stocking anesthesia

Explanation: **Explanation:** In leprosy, the clinical presentation depends on the host's cell-mediated immunity (CMI). **Borderline Leprosy (specifically Borderline Tuberculoid or Borderline Borderline)** is characterized by lesions that are unstable and show features of both ends of the spectrum. **Why Option A is correct:** The **"Inverted Saucer" lesion** (also known as a "Swiss Cheese" appearance) is a classic morphological feature of **Borderline Borderline (BB) leprosy**. These lesions are typically annular or oval plaques with a punched-out, clear center and a sloping outer edge, resembling an inverted saucer. This occurs due to the partial immune response attempting to clear the center of the lesion. **Why the other options are incorrect:** * **Option B (ENL):** Erythema Nodosum Leprosum is a Type 2 Lepra reaction, which is classically seen in **Lepromatous Leprosy (LL)** or near-lepromatous (BL) cases, not typically in the borderline spectrum. * **Option C (Hypopigmented macules all over):** While borderline leprosy has multiple lesions, "all over the body" with symmetrical distribution and numerous small macules is more characteristic of **Lepromatous Leprosy (LL)**. * **Option D (Glove and stocking anesthesia):** This is a feature of distal symmetrical polyneuropathy, most commonly associated with **Lepromatous Leprosy (LL)** due to widespread nerve involvement. **High-Yield Clinical Pearls for NEET-PG:** * **BB Leprosy:** Most unstable form; can shift toward BT (reversal reaction) or BL (downgrading). * **Satellite Lesions:** Small lesions near a larger plaque; highly suggestive of **Borderline Tuberculoid (BT)** leprosy. * **Leonine Facies:** Characteristic of **Lepromatous Leprosy (LL)** due to diffuse infiltration of the face. * **Nerve Involvement:** In Borderline leprosy, nerve involvement is often **asymmetrical** and can be sudden/severe during reactions.

Question 29: The constriction in Ainhum develops usually at which interphalangeal joint?

A. Great toe
B. Little toe (Correct Answer)
C. Thumb
D. Little finger

Explanation: **Explanation:** **Ainhum (Dactylolysis Spontanea)** is a rare, idiopathic condition characterized by the formation of a progressive, constricting fibrous band around the base of a digit. **Why the Little Toe is Correct:** The classic site for Ainhum is the **proximal interphalangeal joint of the fifth (little) toe**. The constriction begins as a groove on the medial or plantar-lateral aspect of the digit, eventually encircling it. This leads to progressive ischemia, bone resorption (rarefaction), and spontaneous auto-amputation. It is most commonly seen in individuals of African descent who walk barefoot in tropical climates. **Analysis of Incorrect Options:** * **Great toe (A):** While other toes can occasionally be involved, the great toe is rarely affected in true Ainhum. * **Thumb (C) & Little finger (D):** Ainhum specifically refers to the toes. Constrictions involving the fingers or multiple digits are typically referred to as **Pseudo-ainhum**, which is associated with genetic conditions (like Vohwinkel syndrome or Mal de Meleda) or physical trauma (like hair-thread tourniquet syndrome). **High-Yield Clinical Pearls for NEET-PG:** * **Radiological Sign:** The "distal tapering" or "conical thinning" of the phalanges (osteolysis) is a characteristic X-ray finding. * **Staging:** It progresses through four stages, ending in auto-amputation. * **Pseudo-ainhum:** Always differentiate from true Ainhum. Pseudo-ainhum is secondary to other conditions (e.g., Leprosy, Psoriasis, Scleroderma, or Keratodermas). * **Treatment:** In early stages, Z-plasty can be performed; late stages require surgical amputation if the digit is painful or non-viable.

Question 30: Which peripheral nerve is most commonly affected in leprosy?

A. Ulnar nerve (Correct Answer)
B. Radial nerve
C. Median nerve
D. Lateral popliteal nerve

Explanation: **Explanation:** Leprosy (*Hansen’s Disease*), caused by *Mycobacterium leprae*, has a unique predilection for peripheral nerves. The bacteria thrive in cooler temperatures (30–33°C), which explains why they preferentially involve superficial nerve trunks located close to the skin surface. **1. Why Ulnar Nerve is Correct:** The **ulnar nerve** is the most commonly affected peripheral nerve in leprosy. It is typically involved at the elbow, just proximal to the olecranon groove (cubital tunnel). Damage leads to sensory loss in the little finger and medial half of the ring finger, and motor weakness resulting in the characteristic **"partial claw hand"** (ape hand). **2. Analysis of Incorrect Options:** * **Radial Nerve:** While frequently involved, it is less common than the ulnar nerve. Involvement usually occurs at the spiral groove, leading to **wrist drop**. * **Median Nerve:** Often involved in conjunction with the ulnar nerve (especially in Borderline Tuberculoid cases), leading to a **"total claw hand"** and "ape thumb" deformity. It is rarely the *most* common or the first nerve affected. * **Lateral Popliteal Nerve (Common Peroneal):** This is the **most commonly affected nerve in the lower limb**. It is involved at the neck of the fibula, leading to **foot drop**. **Clinical Pearls for NEET-PG:** * **Order of involvement (Upper Limb):** Ulnar > Median > Radial. * **Order of involvement (Lower Limb):** Lateral Popliteal > Posterior Tibial. * **Thickest Nerve:** The **Greater Auricular Nerve** is often cited as the most commonly *palpably* enlarged nerve in the head and neck region. * **Facial Nerve:** Involvement leads to lagophthalmos (inability to close the eye), a high-yield clinical sign. * **Nerve Abscess:** Most commonly seen in the **Ulnar nerve** in Tuberculoid (TT) or Borderline Tuberculoid (BT) leprosy.

Practice by Chapter

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Leprosy

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Cutaneous Larva Migrans

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Myiasis

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