Question 1

A 35-year-old man presents with a 2-year history of recurring itchy skin lesions that worsen in winter. His father had a similar condition. Examination reveals Auspitz sign on gentle scraping. The skin findings are shown in Image 1. Which of the following pathophysiological mechanisms is most directly responsible for the sign elicited on scraping in this patient?

Accepted Answer

B. Exposure of dermal papillary capillaries following removal of the suprapapillary epidermal plate in a setting of parakeratosis and thinned granular layer. ***B. Exposure of dermal papillary capillaries following removal of the suprapapillary epidermal plate in a setting of parakeratosis and thinned granular layer***
- The **Auspitz sign** is characterized by pinpoint bleeding when psoriatic scales are removed, resulting from the rupture of **dilated capillaries** within the **dermal papillae**.
- This occurs because the epidermal layer directly above the dermal papillae (the **suprapapillary plate**) is extremely thin, making the underlying blood vessels highly vulnerable to minor trauma.

*A. Loss of cohesion between suprabasal keratinocytes due to autoantibody-mediated desmoglein destruction*
- This describes **acantholysis**, the primary mechanism of **Pemphigus vulgaris**, which leads to intraepidermal blister formation.
- This mechanism is associated with a positive **Nikolsky sign**, not the Auspitz sign or scales typical of psoriasis.

*C. Disruption of the dermoepidermal junction with subepidermal cleft formation and mast cell degranulation*
- This mechanism is characteristic of **Bullous pemphigoid**, where autoantibodies target hemidesmosomes at the **basement membrane zone**.
- It results in tense **subepidermal bullae** rather than the silvery scales and punctate bleeding seen in this patient.

*D. Acanthosis with elongated rete ridges and increased transepidermal water loss causing superficial erosions*
- While **acanthosis** and elongated **rete ridges** are key histopathological features of psoriasis, they do not directly cause the Auspitz sign.
- The pinpoint bleeding is specifically due to the **vascular changes** and the thinning of the epidermis over the papillae, not general transepidermal water loss. [Practice more Dermatology questions on OnCourse]

Question 2

A 9-year-old boy is brought with a 3-week history of patchy hair loss on the scalp associated with mild scaling and broken hair stubs. Several classmates have similar complaints. The school nurse noted the lesions fluoresce under a special lamp. The Wood's lamp examination is shown (Image 1). Which of the following is the most appropriate treatment for this condition?

Accepted Answer

A. Oral griseofulvin for 6–8 weeks with selenium sulfide shampoo. ***A. Oral griseofulvin for 6–8 weeks with selenium sulfide shampoo***
- **Oral griseofulvin** is the traditional first-line treatment for **tinea capitis**, especially when caused by **Microsporum** species, which typically shows **bright yellow-green fluorescence** under a Wood's lamp.
- Adjunctive therapy with **selenium sulfide** or ketoconazole shampoo is recommended to reduce the shedding of **fungal spores** and decrease the risk of transmission to classmates.

*B. Oral fluconazole for 2 weeks with ketoconazole shampoo*
- While **fluconazole** is an alternative systemic antifungal, a 2-week course is generally insufficient; **tinea capitis** requires longer systemic treatment to ensure the fungus is cleared from the **hair follicles**.
- Griseofulvin or **terbinafine** are preferred over fluconazole for pediatric tinea capitis due to more robust clinical evidence for these specific dermatophytes.

*C. Topical clotrimazole cream applied twice daily for 4 weeks*
- **Topical therapy alone** is consistently ineffective for tinea capitis because the fungus resides deep within the **hair shaft** where topical creams cannot penetrate.
- Systemic antifungal medication is mandatory to achieve a clinical and **mycological cure** in scalp infections.

*D. Oral terbinafine for 4 weeks with povidone-iodine shampoo*
- **Terbinafine** is highly effective against **Trichophyton tonsurans**, but it is generally less effective than griseofulvin for infections caused by **Microsporum** species (the likely cause here given the fluorescence).
- Povidone-iodine shampoo is not the standard adjunctive treatment; **antifungal shampoos** like selenium sulfide are preferred to limit the spread of viable spores. [Practice more Dermatology questions on OnCourse]

Question 3

Which Fitzpatrick skin type is most prone to post-inflammatory hyperpigmentation after laser therapy?

Accepted Answer

Type IV-VI. ***Type IV-VI***
 - Individuals with **Fitzpatrick skin types IV-VI** have more active **melanocytes** and higher epidermal melanin, which makes them highly susceptible to **post-inflammatory hyperpigmentation (PIH)** following thermal injury.
 - In these types, any inflammation from **laser therapy** triggers excessive melanin production, necessitating cautious parameter selection and often pre-treatment with **tyrosinase inhibitors**.

*Type I-II*
 - These skin types (pale white to fair) have minimal melanin and typically **burn rather than tan**, making them more prone to **erythema** but less likely to develop hyperpigmentation.
 - The risk of PIH is significantly lower compared to darker skin types because their **melanocytes** are less reactive to inflammatory stimuli.

*Type V-VI*
 - While these types are at extremely high risk, this option is less comprehensive than IV-VI in identifying the full range of patients prone to laser complications.
 - Type V-VI patients specifically carry a high risk for **hypopigmentation** or keloid scarring if laser energy is absorbed excessively by the high baseline **chromophore** density.

*Type III-IV*
 - Type III-IV covers fair to olive skin tones which do carry a moderate risk of PIH, but they are not the *most* prone compared to the category including Type VI.
 - These types typically tan well but do not represent the highest end of the **melanocyte reactivity** spectrum found in darker skin types. [Practice more Dermatology questions on OnCourse]

Question 4

A young female presents with a history of fever and a nodular lesion over the shin. Histopathology reveals foamy histiocytes with neutrophilic infiltration. There is no evidence of vasculitis. What is the most probable diagnosis?

Accepted Answer

Erythema nodosum. ### Explanation

**Correct Answer: B. Erythema nodosum**

**Why it is correct:**
Erythema nodosum (EN) is the most common form of **septal panniculitis**. Clinically, it presents as tender, erythematous nodules typically located over the **pretibial area (shins)**, often accompanied by fever and malaise. Histopathologically, early lesions show edema and neutrophilic infiltration of the septa. As the lesion evolves, it is characterized by **Miescher’s radial granulomas**—small clusters of spindle-shaped or **foamy histiocytes** surrounding a central cleft. The absence of vasculitis is a hallmark feature that distinguishes EN from other forms of panniculitis.

**Why the other options are incorrect:**
*   **A. Sweet’s Syndrome:** This is a neutrophilic dermatosis characterized by "juicy" erythematous plaques and high fever. Histology shows dense dermal neutrophilic infiltrate with papillary dermal edema, but it is not a primary panniculitis and does not typically present with foamy histiocytes in the septa.
*   **C. Erythema nodosum leprosum (ENL):** While ENL also presents with tender nodules and fever, it is a Type 2 Lepra reaction. Histologically, it is a **lobular panniculitis** and, crucially, it **must show evidence of vasculitis** (leukocytoclastic vasculitis) and the presence of *M. leprae* (AFB positive).
*   **D. Behcet’s syndrome:** While it can cause EN-like lesions, the systemic involvement (oral/genital ulcers, uveitis) and the characteristic histopathology (often showing vasculitis) do not fit the isolated description provided.

**NEET-PG High-Yield Pearls:**
*   **Most common cause of EN:** Idiopathic (followed by Streptococcal infections, Sarcoidosis, and TB).
*   **Histopathology Key:** Septal panniculitis **without** vasculitis = Erythema Nodosum.
*   **Löfgren Syndrome:** Triad of EN, bilateral hilar lymphadenopathy, and arthritis (highly suggestive of Sarcoidosis).
*   **Miescher’s Radial Granulomas:** Pathognomonic histological finding for EN. [Practice more Dermatology questions on OnCourse]

Question 5

What is the primary lesion in lichen planus?

Accepted Answer

Papule. **Explanation:**

The primary lesion in **Lichen Planus (LP)** is classically described by the **"6 Ps"**: **P**lanar (flat-topped), **P**urple (violaceous), **P**olygonal, **P**ruritic, **P**apules, and **P**laques.

1.  **Why Papule is Correct:** A papule is a solid, raised lesion less than 1 cm in diameter. In LP, the characteristic lesion is a violaceous, flat-topped papule. These papules often coalesce to form larger **plaques**. The surface of these papules typically shows fine, white, lace-like patterns known as **Wickham striae**, which are a hallmark diagnostic feature.

2.  **Why Other Options are Incorrect:**
    *   **Macule:** This is a flat, non-palpable change in skin color. While post-inflammatory hyperpigmentation (macules) is common after LP heals, the active primary lesion is always raised.
    *   **Vesicle/Bullae:** These are fluid-filled blisters (vesicles <0.5 cm; bullae >0.5 cm). While a rare variant called "Bullous Lichen Planus" exists, these are not the *primary* or most common presentation of the disease.

**High-Yield Clinical Pearls for NEET-PG:**
*   **Histopathology:** Look for the "saw-tooth" appearance of rete pegs, basal cell degeneration (liquefaction necrosis), and a band-like lymphocytic infiltrate at the dermo-epidermal junction.
*   **Koebner Phenomenon:** LP shows a positive Koebner phenomenon (lesions appearing at sites of trauma).
*   **Associations:** Often associated with **Hepatitis C** infection.
*   **Civatte Bodies:** These are apoptotic keratinocytes found in the lower epidermis/upper dermis, also known as colloid or cytoid bodies. [Practice more Dermatology questions on OnCourse]

Dermatology Questions

Topics

Basic Dermatology

Dermatological Pharmacology

Bacterial Skin Infections

Viral Skin Infections

Fungal Skin Infections

Parasitic Skin Infections

Acne and Related Disorders

Pigmentary Disorders

Dermatitis and Eczema

Psoriasis

Blistering Diseases

Autoimmune Skin Diseases

Skin Tumors

Dermatological Procedures

Hair and Nail Disorders

Cosmetic Dermatology

Tropical Dermatology

Pediatric Dermatology

Occupational Dermatoses

Phototherapy and Photobiology

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