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.

Q: A 21-year-old lady on oral contraceptive pills presents with light brown pigmentation of the malar eminences. What is the likely diagnosis?

Melasma. **Explanation:** The clinical presentation of light brown pigmentation over the malar eminences in a young female taking oral contraceptive pills (OCPs) is a classic description of **Melasma**. **Why Melasma is correct:** Melasma (also known as chloasma or the "mask of pregnancy") is an acquired hypermelanosis characterized by symmetrical, irregular, light-to-dark brown macules and patches on sun-exposed areas, most commonly the face (malar, centrofacial, and mandibular patterns). It is primarily driven by **estrogen and progesterone**, which stimulate melanogenesis. Common triggers include pregnancy, OCP use, and UV radiation. **Why the other options are incorrect:** * **Haemochromatosis:** Presents with generalized "bronze" skin pigmentation due to iron deposition, often associated with systemic features like diabetes and cirrhosis, rather than localized facial patches. * **Systemic Lupus Erythematosus (SLE):** Characterized by a "malar rash" (butterfly rash) that is typically **erythematous (red)**, inflammatory, and spares the nasolabial folds. It is not a brown pigmentary disorder. * **Melanoma:** This is a malignant tumor of melanocytes. It usually presents as an asymmetrical, irregular, enlarging pigmented lesion (ABCDE criteria) rather than diffuse, symmetrical patches. **High-Yield Clinical Pearls for NEET-PG:** * **Wood’s Lamp Examination:** Used to determine the depth of pigment. **Epidermal** melasma enhances under Wood’s lamp, while **dermal** melasma does not. * **Treatment:** The gold standard is **Kligman’s Formula** (Triple Combination Therapy): Hydroquinone (lightening agent), Tretinoin (exfoliant), and a mild Corticosteroid (anti-inflammatory). * **Prevention:** Strict photoprotection (broad-spectrum sunscreen) is the most critical step in management.

Q: What concentration of hydroquinone is recommended for treating melasma?

2 to 5%. **Explanation:** Hydroquinone (HQ) is considered the "gold standard" topical therapy for melasma. It acts as a tyrosinase inhibitor, preventing the conversion of L-dopa to melanin. **1. Why 2% to 5% is correct:** The therapeutic window for hydroquinone in clinical practice is typically **2% to 5%**. * **2% concentration** is often available over-the-counter (in some regions) or used for sensitive skin, providing a balance between efficacy and safety. * **4% to 5% concentrations** are the most common prescription strengths (often used in Kligman’s Formula) as they provide maximum depigmenting efficacy. Increasing the concentration beyond 5% significantly raises the risk of severe side effects without a proportional increase in clinical benefit. **2. Analysis of incorrect options:** * **1% to 2% (Options A & B):** While 2% is used, 1% is generally considered sub-therapeutic for significant melasma and is rarely used as a standalone treatment in clinical dermatology. * **10% (Option D):** This is a dangerously high concentration. High strengths of HQ are associated with a high risk of **Exogenous Ochronosis** (asymptomatic blue-black hyperpigmentation) and permanent "confetti-like" depigmentation. **3. Clinical Pearls for NEET-PG:** * **Mechanism of Action:** Inhibition of tyrosinase enzyme. * **Kligman’s Triad (Modified):** Hydroquinone (4%) + Tretinoin (0.05%) + Fluocinolone acetonide (0.01%). This is the most effective treatment for melasma. * **Side Effects:** Contact dermatitis, post-inflammatory hyperpigmentation, and the most high-yield side effect: **Exogenous Ochronosis** (seen with prolonged use or high concentrations). * **Duration:** It is usually recommended to limit use to 3–6 months to prevent complications.

Q: Psoralen 'A' is used in the treatment of which condition?

Vitiligo. ***Vitiligo*** - **Psoralen A** is a photosensitizing agent derived from the **babchi plant** (Psoralea corylifolia) used in **PUVA therapy** (Psoralen + UVA) to stimulate melanocyte activity and repigmentation in vitiligo patches. - It works by increasing **melanin synthesis** when combined with **ultraviolet A radiation**, making it the standard treatment for localized vitiligo lesions. *Pemphigus* - This is an **autoimmune blistering disease** affecting the skin and mucous membranes, treated with **corticosteroids** and **immunosuppressants**. - **Psoralen** has no role in treating **intraepidermal blistering** or controlling autoimmune antibodies against desmogleins. *Pityriasis alba* - This is a **mild eczematous condition** causing hypopigmented patches, typically in children, that resolves spontaneously or with **moisturizers**. - **Psoralen therapy** is not indicated as these patches are **temporary** and **self-limiting**, unlike the permanent depigmentation in vitiligo. *Ichthyosis* - This is a **genetic disorder** characterized by **dry, scaly skin** due to defective keratinization, treated with **emollients** and **keratolytics**. - **Psoralen** has no effect on **skin scaling** or **barrier function** and is not used for keratinization disorders.

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

Question 6

A 21-year-old lady on oral contraceptive pills presents with light brown pigmentation of the malar eminences. What is the likely diagnosis?

Accepted Answer

Melasma

Answer

Haemochromatosis

Answer

Systemic Lupus Erythematosis

Answer

Melanoma

Question 7

Idiopathic guttate hypomelanosis usually occurs over which area of the body?

Accepted Answer

Anterior aspects of legs and forearms

Answer

Face and ears

Answer

Flexural regions

Answer

Extensor surfaces

Question 8

What concentration of hydroquinone is recommended for treating melasma?

Accepted Answer

2 to 5%

Answer

1%

Answer

1 to 2%

Answer

10%

Question 9

A 59-year-old woman presents with increasing skin pigmentation. Physical examination shows hyperkeratosis and hyperpigmentation of the axilla, neck, flexures, and anogenital region. Endocrinologic studies reveal normal serum levels of adrenal corticosteroids and glucocorticoids. If this patient's skin pigmentation represents a paraneoplastic syndrome, the primary tumor would most likely be found in which of the following anatomic locations?

Accepted Answer

Stomach

Answer

Bladder

Answer

Cervix

Answer

Esophagus

Question 10

Psoralen 'A' is used in the treatment of which condition?

Accepted Answer

Vitiligo

Answer

Pemphigus

Answer

Pityriasis alba

Answer

Ichthyosis

Pigmentary Disorders — MCQs

Pigmentary Disorders — MCQs

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