NEET-PG 2025 — Dermatology

Q: A 20-year-old patient presents with a non-progressive hypopigmented lesion on the trunk. On Wood's lamp examination, there is white accentuation. Diascopy is negative. What is the most likely diagnosis?

Nevus depigmentosus. ***Nevus depigmentosus*** - This disorder is a congenital, non-progressive **hypopigmentation** (reduced melanin), which remains constant in size and shape, fitting the clinical scenario. - The lesion shows accentuation (brighter white) under **Wood's lamp**, confirming reduced melanin, and **diascopy is negative** as it is a pigmentary, not vascular, change. *Vitiligo* - Vitiligo is characterized by complete **depigmentation** (leukoderma) due to melanocyte destruction, leading to a stark, **chalk-white** appearance under Wood's lamp. - It is typically a **progressive** symmetrical condition, unlike the static, non-progressive lesion described. *Nevus anemicus* - This is a vascular lesion caused by local exquisite sensitivity to catecholamines, causing **localized vasoconstriction**; hence it is not a true pigment disorder. - The defining feature is a **positive diascopy** (the patch disappears when blanched), which contradicts the negative diascopy in the patient. *Indeterminate leprosy* - Leprosy lesions are hypopigmented patches, but the essential diagnostic criterion is **impaired sensation** (anesthesia or hypoaesthesia), a feature absent from the description. - These patches usually do not show the distinct **white accentuation** seen under Wood's lamp typical of true pigmentary nevi. [Practice more Dermatology PYQs on OnCourse]

Q: A patient presents with an indurated plaque on the cheek with central atrophy. Chest X-ray reveals apical calcification. Which of the following tests is most appropriate to confirm the diagnosis?

PCR. ***PCR*** - The clinical picture of an indurated plaque (often exhibiting **apple-jelly nodules** on diascopy) with central atrophy, coupled with radiological evidence of old pulmonary TB (apical calcification), strongly suggests **Lupus Vulgaris** (cutaneous tuberculosis). - **PCR (Polymerase Chain Reaction)** is the most sensitive and specific method for confirming the diagnosis by detecting *Mycobacterium tuberculosis* DNA, which is essential as Lupus Vulgaris is typically a **paucibacillary** condition where AFB staining and culture often fail. *Mantoux test* - The **Mantoux test** assesses delayed-type hypersensitivity (Type IV reaction) to tuberculin antigens and indicates prior exposure to TB or BCG vaccination. - It is useful for screening but **does not confirm active disease** (Lupus Vulgaris) and can be negative in immunocompromised patients or anergic forms. *Slit skin smear* - **Slit skin smear** is the diagnostic method primarily used to detect **acid-fast bacilli** (*M. leprae*) and classify **Leprosy** (Hansen's disease). - It is **not the investigation of choice** for diagnosing tuberculosis. *Probe test* - Nucleic acid **probe tests** (hybridization) are molecular techniques used to identify *M. tuberculosis* but are generally less sensitive than modern **PCR** assays, especially when dealing with limited tissue samples or low bacterial load. - **PCR** is the superior and more widely employed molecular diagnostic standard for confirming paucibacillary TB. [Practice more Dermatology PYQs on OnCourse]

Q: A woman presents with pruritic rash on the elbows, buttocks with recent diagnosis of gluten sensitive enteropathy. On immunofluorescence IgA deposition is seen as shown in the image. What is the most likely diagnosis?

Dermatitis herpetiformis. ***Dermatitis herpetiformis*** - The combination of severely **pruritic, grouped vesicles (herpetiform)** on extensor surfaces (elbows, buttocks) and underlying **gluten-sensitive enteropathy** is pathognomonic. - The immunofluorescence image demonstrates characteristic **granular IgA deposition** specifically in the **dermal papillae**, which confirms the diagnosis. *Pemphigus vulgaris* - DIF typically shows a **"fishnet" pattern** of **IgG and C3** deposition in the **intercellular spaces** of the epidermis. - Clinically presents with **flaccid intraepidermal bullae** and extensive mucosal erosions, which is distinct from the patient's presentation. *Bullous pemphigoid* - DIF is characterized by **linear deposition of IgG and C3 along the basement membrane zone** (BMZ), not granular IgA in the dermal papillae. - Clinically, it presents with **tense bullae**, often in the elderly, and is not linked to gluten-sensitive enteropathy. *Psoriasis* - This condition is characterized by **erythematous plaques with silvery scales** (Koebner phenomenon is common) and is a papulosquamous disorder, not a bullous disease. - The histopathology involves acanthosis and Munro microabscesses, and it lacks the specific **IgA deposits** seen in the image. [Practice more Dermatology PYQs on OnCourse]

3 Previous Year Questions with Answers & Explanations

Questions

A 20-year-old patient presents with a non-progressive hypopigmented lesion on the trunk. On Wood's lamp examination, there is white accentuation. Diascopy is negative. What is the most likely diagnosis?

A patient presents with an indurated plaque on the cheek with central atrophy. Chest X-ray reveals apical calcification. Which of the following tests is most appropriate to confirm the diagnosis?

A woman presents with pruritic rash on the elbows, buttocks with recent diagnosis of gluten sensitive enteropathy. On immunofluorescence IgA deposition is seen as shown in the image. What is the most likely diagnosis?

NEET-PG 2025 - Dermatology NEET-PG Practice Questions and MCQs

Question 1: A 20-year-old patient presents with a non-progressive hypopigmented lesion on the trunk. On Wood's lamp examination, there is white accentuation. Diascopy is negative. What is the most likely diagnosis?

A. Nevus anemicus
B. Nevus depigmentosus (Correct Answer)
C. Indeterminate leprosy
D. Vitiligo

Explanation: ***Nevus depigmentosus*** - This disorder is a congenital, non-progressive **hypopigmentation** (reduced melanin), which remains constant in size and shape, fitting the clinical scenario. - The lesion shows accentuation (brighter white) under **Wood's lamp**, confirming reduced melanin, and **diascopy is negative** as it is a pigmentary, not vascular, change. *Vitiligo* - Vitiligo is characterized by complete **depigmentation** (leukoderma) due to melanocyte destruction, leading to a stark, **chalk-white** appearance under Wood's lamp. - It is typically a **progressive** symmetrical condition, unlike the static, non-progressive lesion described. *Nevus anemicus* - This is a vascular lesion caused by local exquisite sensitivity to catecholamines, causing **localized vasoconstriction**; hence it is not a true pigment disorder. - The defining feature is a **positive diascopy** (the patch disappears when blanched), which contradicts the negative diascopy in the patient. *Indeterminate leprosy* - Leprosy lesions are hypopigmented patches, but the essential diagnostic criterion is **impaired sensation** (anesthesia or hypoaesthesia), a feature absent from the description. - These patches usually do not show the distinct **white accentuation** seen under Wood's lamp typical of true pigmentary nevi.

Question 2: A patient presents with an indurated plaque on the cheek with central atrophy. Chest X-ray reveals apical calcification. Which of the following tests is most appropriate to confirm the diagnosis?

A. Mantoux test
B. Slit skin smear
C. PCR (Correct Answer)
D. Probe test

Explanation: ***PCR*** - The clinical picture of an indurated plaque (often exhibiting **apple-jelly nodules** on diascopy) with central atrophy, coupled with radiological evidence of old pulmonary TB (apical calcification), strongly suggests **Lupus Vulgaris** (cutaneous tuberculosis). - **PCR (Polymerase Chain Reaction)** is the most sensitive and specific method for confirming the diagnosis by detecting *Mycobacterium tuberculosis* DNA, which is essential as Lupus Vulgaris is typically a **paucibacillary** condition where AFB staining and culture often fail. *Mantoux test* - The **Mantoux test** assesses delayed-type hypersensitivity (Type IV reaction) to tuberculin antigens and indicates prior exposure to TB or BCG vaccination. - It is useful for screening but **does not confirm active disease** (Lupus Vulgaris) and can be negative in immunocompromised patients or anergic forms. *Slit skin smear* - **Slit skin smear** is the diagnostic method primarily used to detect **acid-fast bacilli** (*M. leprae*) and classify **Leprosy** (Hansen's disease). - It is **not the investigation of choice** for diagnosing tuberculosis. *Probe test* - Nucleic acid **probe tests** (hybridization) are molecular techniques used to identify *M. tuberculosis* but are generally less sensitive than modern **PCR** assays, especially when dealing with limited tissue samples or low bacterial load. - **PCR** is the superior and more widely employed molecular diagnostic standard for confirming paucibacillary TB.

Question 3: A woman presents with pruritic rash on the elbows, buttocks with recent diagnosis of gluten sensitive enteropathy. On immunofluorescence IgA deposition is seen as shown in the image. What is the most likely diagnosis?

A. Psoriasis
B. Dermatitis herpetiformis (Correct Answer)
C. Bullous pemphigoid
D. Pemphigus vulgaris

Explanation: ***Dermatitis herpetiformis*** - The combination of severely **pruritic, grouped vesicles (herpetiform)** on extensor surfaces (elbows, buttocks) and underlying **gluten-sensitive enteropathy** is pathognomonic. - The immunofluorescence image demonstrates characteristic **granular IgA deposition** specifically in the **dermal papillae**, which confirms the diagnosis. *Pemphigus vulgaris* - DIF typically shows a **"fishnet" pattern** of **IgG and C3** deposition in the **intercellular spaces** of the epidermis. - Clinically presents with **flaccid intraepidermal bullae** and extensive mucosal erosions, which is distinct from the patient's presentation. *Bullous pemphigoid* - DIF is characterized by **linear deposition of IgG and C3 along the basement membrane zone** (BMZ), not granular IgA in the dermal papillae. - Clinically, it presents with **tense bullae**, often in the elderly, and is not linked to gluten-sensitive enteropathy. *Psoriasis* - This condition is characterized by **erythematous plaques with silvery scales** (Koebner phenomenon is common) and is a papulosquamous disorder, not a bullous disease. - The histopathology involves acanthosis and Munro microabscesses, and it lacks the specific **IgA deposits** seen in the image.