Pigmentary Disorders Practice Questions

Q: A 50-year-old man with Fitzpatrick skin type V desires treatment for melasma. He was previously treated with triple combination cream with partial response. What would be the most evidence-based next step considering safety and efficacy?

Q-switched Nd:YAG laser 1064 nm with low fluence. ***Q-switched Nd:YAG laser 1064 nm with low fluence*** - This approach, often called **laser toning**, uses a long wavelength that spares the epidermis, making it the safest laser option for **Fitzpatrick skin type V** to avoid **post-inflammatory hyperpigmentation (PIH)**. - It is a clinically sound next step for **recalcitrant melasma** that has only partially responded to first-line therapies like **triple combination cream**. *Fractional CO2 laser resurfacing* - This is an **ablative** treatment that causes significant thermal damage, which carries an unacceptably high risk of **PIH** and scarring in darker skin types. - While effective for skin remodeling, it is generally contraindicated for treating melasma in **type V skin** due to the likelihood of worsening the pigmentation. *Intense pulsed light therapy* - **IPL** uses a broad spectrum of light which is poorly targeted for melasma in dark-skinned individuals and is frequently associated with **rebound hyperpigmentation**. - The melanin in the surrounding **darker skin (Type V)** competes for the energy, leading to a high risk of **thermal burns** and uneven results. *TCA 35% chemical peel* - A 35% concentration of **Trichloroacetic acid (TCA)** is considered a **medium-depth peel**, which is generally too aggressive for patients with Fitzpatrick skin type V. - Medium-depth peels in dark skin types are likely to cause **persistent dyschromia** or permanent **hypopigmentation**, whereas superficial peels (like glycolic or salicylic acid) are safer.

Q: What is the most common association with Acanthosis nigricans?

Obesity. **Explanation:** **Acanthosis Nigricans (AN)** is a common dermatological condition characterized by hyperpigmented, velvety plaques, typically found in intertriginous areas like the axilla and neck. **Why Obesity is the Correct Answer:** Obesity is the **most common** association and cause of Acanthosis Nigricans (Pseudo-acanthosis nigricans). The underlying mechanism is **Insulin Resistance**. In obese individuals, high levels of circulating insulin bind to **Insulin-like Growth Factor-1 (IGF-1) receptors** on keratinocytes and fibroblasts. This stimulates excessive proliferation of these cells, leading to the characteristic epidermal thickening and hyperpigmentation. **Analysis of Incorrect Options:** * **Diabetes Mellitus (B):** While AN is a strong cutaneous marker for Type 2 Diabetes, it usually precedes the clinical onset of diabetes. Obesity remains the primary driver and more frequent association. * **Hypertension (A) & Hypothyroidism (D):** These are often part of the "Metabolic Syndrome" or associated endocrinopathies (like PCOS), but they are not the primary or most common cause of the skin changes seen in AN. **High-Yield Clinical Pearls for NEET-PG:** * **Malignant Acanthosis Nigricans:** If AN appears suddenly, is very extensive, or involves the palms (**Tripe Palms**) and oral mucosa, it is highly suggestive of internal malignancy, most commonly **Gastric Adenocarcinoma**. * **Histopathology:** Shows hyperkeratosis and papillomatosis. Note that "acanthosis" (thickening of the stratum spinosum) is actually minimal despite the name. * **Common Sites:** Neck (most common), axilla, groins, and knuckles. * **Drug-induced AN:** Can be caused by Nicotinic acid, systemic corticosteroids, and OCPs.

Q: An increased incidence of vitiligo is found in association with which of the following conditions?

Diabetes mellitus. **Explanation:** **Vitiligo** is a chronic autoimmune skin disorder characterized by the destruction of melanocytes. The key medical concept to understand for NEET-PG is that vitiligo is frequently associated with other **organ-specific autoimmune disorders**. **1. Why Diabetes Mellitus is correct:** Vitiligo is part of a spectrum of autoimmune polyendocrine syndromes. There is a statistically significant association between vitiligo and **Type 1 Diabetes Mellitus** (and occasionally Type 2) due to shared genetic susceptibility and autoimmune pathways. Other common associations include: * **Thyroid disorders** (most common association, especially Hashimoto’s thyroiditis). * Pernicious anemia. * Addison’s disease. * Alopecia areata. **2. Why the other options are incorrect:** * **Psoriasis (A):** While both are T-cell mediated inflammatory skin diseases, psoriasis is not classically associated with the systemic autoimmune cluster seen in vitiligo. * **Nutritional deficiency (B):** Vitiligo is an autoimmune process, not a nutritional one. While some studies suggest low Vitamin B12 or Vitamin D levels in vitiligo patients, deficiency is not a causative or strongly associated factor. * **Old age (C):** Vitiligo typically has an early onset; 50% of cases begin before age 20. It is not a degenerative condition of aging. **High-Yield Clinical Pearls for NEET-PG:** * **Most common association:** Thyroid dysfunction (check TSH in vitiligo patients). * **Koebner Phenomenon:** Vitiligo shows positivity (depigmentation at sites of trauma). * **Vogt-Koyanagi-Harada Syndrome:** Vitiligo associated with uveitis, meningitis, and auditory symptoms. * **Treatment of choice:** Narrowband UVB (NB-UVB) is the gold standard for generalized vitiligo.

Q: Fine reticular pigmentation with palmar pits is seen in which of the following conditions?

Dowling-Degos disease. **Explanation:** **Dowling-Degos Disease (DDD)** is an autosomal dominant genodermatosis characterized by a defect in the **KRT5 gene** (Keratin 5). The hallmark clinical presentation is **fine, reticulate (lace-like) hyperpigmentation** that typically begins in the axillae and groin and later spreads to other flexures. A diagnostic clinical clue for DDD is the presence of **pitted perioral scars** and **comedo-like lesions** (dark keratinous plugs) on the neck and back, along with **palmar pits**. Histologically, it shows "antler-like" or "filiform" downward extensions of the epidermis with hyperpigmentation of the tips. **Why the other options are incorrect:** * **Rothmund-Thomson Syndrome:** Characterized by **poikiloderma** (atrophy, telangiectasia, and mottled pigmentation) starting on the cheeks, associated with juvenile cataracts and skeletal abnormalities. * **Cockayne Syndrome:** A DNA repair defect presenting with **cachectic dwarfism**, "bird-like" facies, and extreme photosensitivity, but lacks reticulate pigmentation or palmar pits. * **Bloom Syndrome:** Features a characteristic **malar "butterfly" rash** (photosensitive telangiectatic erythema) and proportional short stature due to chromosomal instability (BLM gene). **High-Yield Clinical Pearls for NEET-PG:** * **Reticulate Pigmentation Spectrum:** If the question mentions reticulate pigmentation *plus* hypopigmented macules and nail dystrophy, think of **Dyskeratosis Congenita**. * **Kitamura Reticulate Acropigmentation:** Similar to DDD but involves the **dorsum of hands and feet** (acral distribution) and is associated with the *ADAM10* gene. * **Palmar Pits Triad:** Always remember the three major causes of palmar pits: **Dowling-Degos Disease**, **Gorlin Syndrome** (Basal Cell Nevus Syndrome), and **Darier Disease**.

Q: A child presents with a 2x2 cm depigmented macule with irregular margins over the forehead and glabella. There is a white forelock over the forehead since birth. What is the most likely diagnosis?

Piebaldism. **Explanation:** The clinical presentation of a **congenital depigmented macule** associated with a **white forelock (poliosis)** is the classic hallmark of **Piebaldism**. **1. Why Piebaldism is Correct:** Piebaldism is an autosomal dominant disorder caused by a mutation in the **KIT proto-oncogene**, which leads to defective migration and differentiation of melanoblasts from the neural crest to the skin during embryogenesis. Key features include: * **Congenital presence:** Present since birth (unlike vitiligo). * **White Forelock:** Occurs in 80-90% of cases, typically in a triangular or diamond shape. * **Distribution:** Depigmented patches usually involve the central forehead, trunk, and extremities, often with "islands" of normal pigmentation within the patches. **2. Why Other Options are Incorrect:** * **Dermatitis:** This is an inflammatory skin condition characterized by erythema, scaling, and itching. While post-inflammatory hypopigmentation can occur, it is not congenital and does not present with a white forelock. * **Vitiligo:** This is an acquired autoimmune destruction of melanocytes. It typically appears later in life, is progressive, and lacks the stable, congenital pattern seen here. * **Nevus of Ito:** This is a dermal melanocytosis presenting as a **bluish-gray hyperpigmented** patch (not depigmented) along the distribution of the posterior supraclavicular and lateral cutaneous brachial nerves. **Clinical Pearls for NEET-PG:** * **Differential Diagnosis:** Always differentiate Piebaldism from **Waardenburg Syndrome**, which also features a white forelock but includes systemic findings like sensorineural deafness and heterochromia iridis. * **Stability:** Unlike Vitiligo, the patches in Piebaldism are stable and do not change significantly in size throughout life. * **Histopathology:** Shows a complete absence of melanocytes in the depigmented areas.

Question 1

A 50-year-old man with Fitzpatrick skin type V desires treatment for melasma. He was previously treated with triple combination cream with partial response. What would be the most evidence-based next step considering safety and efficacy?

Accepted Answer

Q-switched Nd:YAG laser 1064 nm with low fluence

Answer

Fractional CO2 laser resurfacing

Answer

Intense pulsed light therapy

Answer

TCA 35% chemical peel

Question 2

What is the most common association with Acanthosis nigricans?

Accepted Answer

Obesity

Answer

Hypertension

Answer

Diabetes Mellitus

Answer

Hypothyroidism

Question 3

An increased incidence of vitiligo is found in association with which of the following conditions?

Accepted Answer

Diabetes mellitus

Answer

Psoriasis

Answer

Nutritional deficiency

Answer

Old age

Question 4

Fine reticular pigmentation with palmar pits is seen in which of the following conditions?

Accepted Answer

Dowling-Degos disease

Answer

Rothmund-Thomson syndrome

Answer

Cockayne syndrome

Answer

Bloom syndrome

Question 5

A child presents with a 2x2 cm depigmented macule with irregular margins over the forehead and glabella. There is a white forelock over the forehead since birth. What is the most likely diagnosis?

Accepted Answer

Piebaldism

Answer

Dermatitis

Answer

Vitiligo

Answer

Nevus of Ito

Pigmentary Disorders — MCQs

Pigmentary Disorders — MCQs

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