Tropical Dermatology Practice Questions

Q: Which of the following conditions is characterized by the sign of the groove?

Lymphogranuloma venereum. **Explanation:** **Lymphogranuloma venereum (LGV)** is caused by the **L1, L2, and L3 serovars of *Chlamydia trachomatis***. The "Sign of the Groove" (Greenblatt’s sign) is a pathognomonic clinical finding in the secondary stage of LGV. It occurs when the inguinal and femoral lymph nodes enlarge simultaneously, separated by the rigid **inguinal ligament**. This creates a visible depression or "groove" between the two groups of inflamed lymph nodes. **Analysis of Incorrect Options:** * **B. Granuloma Inguinale (Donovanosis):** Caused by *Klebsiella granulomatis*. It presents with painless, beefy-red, velvety ulcers. It is characterized by "pseudobuboes" (subcutaneous granulation tissue) rather than true lymphadenopathy. * **C. Syphilis:** Primary syphilis presents with a painless, indurated "hard chancre." While it causes bilateral inguinal lymphadenopathy, the nodes are discrete, rubbery, and do not form a groove. * **D. Chancroid:** Caused by *Haemophilus ducreyi*. It presents with painful, soft ulcers and painful inflammatory buboes that are usually unilateral and may suppurate, but they do not form the characteristic groove sign. **High-Yield Clinical Pearls for NEET-PG:** * **Stages of LGV:** Primary (painless papule/ulcer), Secondary (Inguinal syndrome with the Groove sign), and Tertiary (Genito-anorectal syndrome/Elephantiasis). * **Diagnosis:** Frei test (historical), NAAT (current gold standard), and **Donovan bodies** (safety-pin appearance) are seen in Donovanosis, NOT LGV. * **Treatment:** Doxycycline (100 mg BID for 21 days) is the drug of choice for LGV.

Q: A child from Bihar presents with hypopigmented patches on the face. What is the most likely diagnosis?

Leprosy. **Explanation:** In the context of NEET-PG, the geographical location provided in a clinical stem is a critical diagnostic clue. **Bihar** is a highly endemic region for **Leprosy (Hansen’s Disease)** in India. In an endemic area, any hypopigmented patch in a child should be considered Leprosy until proven otherwise. The diagnosis is clinically supported by the presence of sensory loss (anesthesia/hypoesthesia) within the patch and/or thickened peripheral nerves. **Analysis of Options:** * **Leprosy (Correct):** The most common presentation in children is a solitary, ill-defined hypopigmented patch (Tuberculoid or Indeterminate spectrum). The epidemiological link to Bihar makes this the most likely diagnosis for exam purposes. * **Pityriasis alba:** This also presents as hypopigmented patches on the face of children, often associated with atopy. However, the patches usually have fine scaling and lack the sensory loss or nerve involvement characteristic of Leprosy. * **Vitiligo:** This presents as "depigmented" (chalky white) macules rather than "hypopigmented" patches. The borders are usually well-defined, and sensation remains intact. **Clinical Pearls for NEET-PG:** * **Cardinal Signs of Leprosy:** 1. Hypopigmented/erythematous patches with definite loss of sensation. 2. Thickened/tender peripheral nerves. 3. Positive skin smear for Acid Fast Bacilli (*M. leprae*). * **Differential Diagnosis:** For a hypopigmented patch on the face, always consider *Pityriasis versicolor* (fungal, "spaghetti and meatballs" appearance on KOH) and *Post-inflammatory hypopigmentation*. * **High-Yield Fact:** The most common nerve involved in Leprosy is the **Ulnar nerve**, but the most common nerve involved in the face is the **Zygomatic branch of the Facial nerve** (leading to lagophthalmos).

Q: An 8-year-old boy presents with a white, non-anesthetic, non-scaly hypopigmented macule on his face. What is the likely diagnosis?

Indeterminate leprosy. ### Explanation The correct diagnosis is **Indeterminate Leprosy**. This is the earliest clinical stage of leprosy, often seen in children. It typically presents as a single, poorly defined, hypopigmented macule, most commonly on the face, extensor surfaces, or buttocks. **Why Indeterminate Leprosy is correct:** In the early stages of leprosy, nerve damage is not yet extensive. Therefore, the classic signs of leprosy—such as **anesthesia** (loss of sensation) and **anhidrosis** (loss of sweating)—are frequently **absent**. The presence of a non-anesthetic, non-scaly hypopigmented macule in an endemic area should always raise suspicion for indeterminate leprosy. **Why the other options are incorrect:** * **Pityriasis alba:** While it also presents as hypopigmented macules on the face of children, it is characterized by **fine, powdery scaling** and is often associated with atopic dermatitis. * **Pityriasis versicolor:** This fungal infection presents with **fine scaling** (demonstrated by the "coup d'ongle" or scratch sign) and typically affects the trunk rather than the face in children. * **Neuritic leprosy:** This form involves nerve trunks without any visible skin lesions. It presents with motor weakness, sensory loss, or nerve thickening, but not with a hypopigmented macule. **NEET-PG High-Yield Pearls:** * **Indeterminate Leprosy:** Most cases (approx. 75%) self-heal; others evolve into the polar forms (TT or LL) depending on the patient's cell-mediated immunity. * **Histopathology:** Shows a non-specific perivascular and periappendageal lymphocytic infiltrate. Acid-fast bacilli (AFB) are rarely found. * **Clinical Tip:** If a hypopigmented patch on a child's face is **non-scaly** and **non-itchy**, think Indeterminate Leprosy first in the Indian context.

Q: Which of the following is least likely to be a mode of transmission of Hansen's disease?

Transplacental. **Explanation:** Hansen’s disease (Leprosy), caused by *Mycobacterium leprae*, primarily spreads through prolonged, close contact with untreated multibacillary patients. **1. Why Transplacental is the Correct Answer:** While *M. leprae* has been detected in the placenta and umbilical cord blood of infected mothers, **congenital transmission (transplacental) is extremely rare and considered the least likely mode of transmission.** Most children born to mothers with leprosy are born healthy. The risk to the infant primarily arises from post-natal exposure to the mother’s respiratory droplets or skin contact rather than intrauterine infection. **2. Analysis of Other Options:** * **Droplet Infection (Option B):** This is the **most common and primary route** of transmission. Large numbers of bacilli are shed from the nasal mucosa of untreated lepromatous patients during sneezing or coughing. * **Breast Milk (Option D):** *M. leprae* has been demonstrated in the breast milk of lactating mothers with lepromatous leprosy. While not the primary route, it is a documented potential vehicle for transmission. * **Mosquito Bite (Option A):** Arthropod vectors (mosquitos, bedbugs, and flies) have been shown to carry *M. leprae* mechanically. While their epidemiological significance is debated, they are recognized as a possible minor mode of transmission in endemic areas. **Clinical Pearls for NEET-PG:** * **Incubation Period:** Longest among bacterial infections (Average: 3–5 years). * **Primary Site of Entry:** Respiratory tract (nasal mucosa) is the most accepted portal of entry. * **Armadillos:** Known natural non-human reservoirs of *M. leprae*. * **Cooler Temperatures:** The organism prefers temperatures of 27–30°C, explaining its predilection for peripheral nerves, skin, and the anterior chamber of the eye.

Q: In Hansen's disease, which nerve is commonly affected at the elbow?

Ulnar nerve. **Explanation:** **Hansen’s Disease (Leprosy)** is a chronic infectious disease caused by *Mycobacterium leprae*, which has a unique predilection for peripheral nerves. The bacteria prefer cooler temperatures, which is why they primarily affect superficial nerve trunks located near the skin surface. **Why the Ulnar Nerve is Correct:** The **ulnar nerve** is the most commonly affected peripheral nerve in leprosy. At the elbow, it passes through the **cubital tunnel** (behind the medial epicondyle), where it is superficial and subject to lower temperatures. This environment facilitates the proliferation of *M. leprae*, leading to nerve thickening (neuritis) and subsequent motor/sensory loss. Involvement here typically results in a "Claw Hand" deformity (specifically the ring and little fingers). **Analysis of Incorrect Options:** * **Median Nerve:** While frequently involved in leprosy, it is typically affected at the **wrist** (within the carpal tunnel), not the elbow. Its involvement leads to "Ape Thumb" deformity. * **Radial Nerve:** This nerve is less commonly affected than the ulnar or median nerves. When involved, it usually occurs in the **radial groove** of the humerus, leading to "Wrist Drop." * **Musculocutaneous Nerve:** This nerve is rarely involved in leprosy as it is deeply situated within the musculature of the arm. **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 (leads to Foot Drop). * **Nerve thickening:** Always palpate the nerve proximal to the site of entrapment (e.g., palpate the ulnar nerve just above the medial epicondyle). * **Facial Nerve:** The most common cranial nerve involved, leading to Lagophthalmos. * **Great Auricular Nerve:** Often visibly thickened in the neck; it is a purely sensory nerve.

Question 1

Which of the following conditions is characterized by the sign of the groove?

Accepted Answer

Lymphogranuloma venereum

Answer

Granuloma inguinale

Answer

Syphilis

Answer

Chancroid

Question 2

A child from Bihar presents with hypopigmented patches on the face. What is the most likely diagnosis?

Accepted Answer

Leprosy

Answer

Pityriasis alba

Answer

Vitiligo

Answer

None of the above

Question 3

An 8-year-old boy presents with a white, non-anesthetic, non-scaly hypopigmented macule on his face. What is the likely diagnosis?

Accepted Answer

Indeterminate leprosy

Answer

Pityriasis alba

Answer

Pityriasis versicolor

Answer

Neuritic leprosy

Question 4

Which of the following is least likely to be a mode of transmission of Hansen's disease?

Accepted Answer

Transplacental

Answer

Mosquito bite

Answer

Droplet infection

Answer

Breast milk

Question 5

In Hansen's disease, which nerve is commonly affected at the elbow?

Accepted Answer

Ulnar nerve

Answer

Median nerve

Answer

Radial nerve

Answer

Musculocutaneous nerve

Tropical Dermatology — MCQs

Tropical Dermatology — MCQs

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