Pigmentary Disorders Practice Questions

Q: A female presents with hypopigmented lesions on the central forehead. Which drug is responsible?

Para tertiary butyl phenol. **Explanation:** The correct answer is **Para tertiary butyl phenol (PTBP)**. This condition is known as **Chemical Leucoderma** (or Contact Vitiligo). **Why PTBP is correct:** PTBP is a common antioxidant and adhesive used in the manufacturing of **bindis**, rubber, and adhesives. In the Indian context, "Bindi-induced depigmentation" is a classic clinical presentation. PTBP acts as a potent melanocytotoxin; it is structurally similar to tyrosine and competes for the enzyme tyrosinase, leading to the selective destruction of melanocytes and subsequent hypopigmented or depigmented patches at the site of contact (typically the central forehead). **Analysis of Incorrect Options:** * **A. Hydroquinone:** Primarily used as a skin-lightening agent for melasma. While it can cause "confetti-like" depigmentation if used in high concentrations, it is not the primary cause of bindi-induced leucoderma. * **B. Ether metabolite of hydroquinone (Monobenzyl ether of hydroquinone):** This is a potent permanent depigmenting agent used to treat extensive vitiligo (depigmentation therapy). It causes systemic depigmentation, not localized bindi-pattern lesions. * **C. Para tertiary butyl catechol:** Used in the production of resins and plastics. While it can cause chemical leucoderma, it is less commonly associated with bindi adhesives compared to PTBP. **High-Yield Clinical Pearls for NEET-PG:** * **Common Culprits:** PTBP (Bindis), Monobenzyl ether of hydroquinone (Rubber gloves/condoms), and P-phenylenediamine (Hair dyes). * **Clinical Feature:** Unlike Vitiligo, chemical leucoderma often shows "confetti-like" macules at the periphery and lacks the Koebner phenomenon. * **Diagnosis:** Primarily clinical; Patch testing with PTBP (1% in petrolatum) can confirm the sensitivity. * **Treatment:** Immediate cessation of the offending agent; topical steroids or calcineurin inhibitors may help in repigmentation.

Q: Vitiligo is commonly associated with which of the following conditions?

Diabetes mellitus. **Explanation:** Vitiligo is a common, acquired pigmentary disorder characterized by the autoimmune destruction of melanocytes. The key medical concept to remember for NEET-PG is that **vitiligo is frequently part of a polyautoimmune syndrome.** **Why Diabetes Mellitus is correct:** Vitiligo is strongly associated with other organ-specific autoimmune diseases. **Type 1 Diabetes Mellitus** is a well-documented association due to shared genetic susceptibility and common autoimmune pathways. Patients with vitiligo have a higher prevalence of thyroid disorders (most common), Type 1 DM, Addison’s disease, and Pernicious anemia. **Analysis of Incorrect Options:** * **Celiac Sprue:** While an autoimmune condition, it is not classically or frequently associated with vitiligo compared to endocrine autoimmune disorders. * **Polycystic Ovarian Disease (PCOS):** This is a metabolic and hormonal disorder, not an autoimmune destruction of tissue, and has no established link with vitiligo. * **Alpha-1 Antitrypsin Deficiency:** This is a genetic protein deficiency affecting the lungs and liver; it does not share an autoimmune pathophysiology with vitiligo. **High-Yield Clinical Pearls for NEET-PG:** * **Most common association:** Hashimoto’s thyroiditis (Autoimmune Thyroid Disease) is the #1 association. * **Vogt-Koyanagi-Harada (VKH) Syndrome:** A multisystem disorder involving vitiligo, poliosis, uveitis, and auditory symptoms. * **Koebner Phenomenon:** Vitiligo exhibits this (development of lesions at sites of trauma), similar to Psoriasis and Lichen Planus. * **Treatment of Choice:** Narrowband UVB (NB-UVB) is currently the gold standard for generalized vitiligo.

Q: A large, dark brown patch is noted on the back. What is the most likely diagnosis?

Becker nevus. ***Becker nevus*** - **Large, dark brown patch** on the back is characteristic of Becker nevus, which typically appears as an **irregular, unilateral pigmented patch** on the **upper trunk** or **shoulder area**. - Often develops during **adolescence** and may be associated with **hypertrichosis** (excessive hair growth) within the lesion, predominantly affecting **males**. *Seborrheic melanosis* - Appears as **multiple, well-demarcated brown patches** with a **"stuck-on" appearance** and **warty surface texture**, unlike the smooth patch described. - More commonly seen in **elderly patients** and typically involves **sun-exposed areas** like the face and chest. *Lichen planus pigmentosus* - Presents as **multiple small, dark brown macules** in a **bilateral symmetric distribution**, not as a single large patch. - Often associated with **mucous membrane involvement** and **nail changes**, which are not mentioned in this case. *Pityriasis versicolor* - Characterized by **multiple small, scaly patches** that are typically **lighter or darker** than surrounding skin with a **fine scale**. - Caused by **Malassezia fungus** and shows **yellow fluorescence** under **Wood's lamp examination**, unlike the single dark patch described.

Q: Which of the following conditions are associated with acanthosis nigricans?

Carcinoma of the stomach, Obesity, and Insulin resistance. **Explanation:** **Acanthosis Nigricans (AN)** is a clinical marker characterized by hyperpigmented, velvety, and papillomatous plaques, most commonly found in intertriginous areas like the axilla and neck. **1. Why Option C is Correct:** The pathogenesis of AN involves the stimulation of **Insulin-like Growth Factor (IGF-1) receptors** or **Fibroblast Growth Factor Receptors (FGFR)** on keratinocytes and fibroblasts, leading to epidermal proliferation. * **Obesity and Insulin Resistance:** These are the most common causes (Type II AN). High levels of circulating insulin cross-react with IGF-1 receptors. * **Carcinoma of the stomach:** This is the classic association for **Malignant Acanthosis Nigricans**. It is a paraneoplastic syndrome caused by the secretion of Transforming Growth Factor-alpha (TGF-α) by the tumor, which acts on Epidermal Growth Factor Receptors (EGFR). **2. Why Other Options are Incorrect:** * **Options A & B:** These are incomplete. While gastric cancer is associated, AN is far more frequently seen in metabolic conditions like obesity. * **Hemochromatosis (Options B & D):** This condition causes generalized "bronzing" of the skin due to melanin and iron deposition, but it is **not** typically associated with the velvety plaques of acanthosis nigricans. **Clinical Pearls for NEET-PG:** * **Malignant AN:** Usually sudden onset, extensive, and involves unconventional sites like the palms (**Tripe palms**) or oral mucosa. Gastric adenocarcinoma is the most common underlying malignancy. * **Sign of Leser-Trélat:** The sudden eruption of multiple seborrheic keratoses, often associated with malignant AN. * **Drug-induced AN:** Can be caused by Nicotinic acid, systemic corticosteroids, and OCPs. * **Histopathology:** Shows hyperkeratosis and papillomatosis; surprisingly, "acanthosis" (thickening of the stratum spinosum) is often minimal despite the name.

Q: In an elderly patient, acanthosis nigricans usually indicates what?

Malignancy. **Explanation:** **Acanthosis Nigricans (AN)** is a clinical sign characterized by hyperpigmented, velvety, and verrucous plaques, most commonly involving intertriginous areas like the axilla, neck, and groin. **Why Malignancy is the Correct Answer:** While AN is most commonly associated with insulin resistance and obesity (Pseudo-AN), its sudden onset in an **elderly patient** is a classic "red flag" for **Malignant Acanthosis Nigricans**. This is a paraneoplastic syndrome, most frequently associated with **adenocarcinomas of the gastrointestinal tract** (specifically the stomach in 55-60% of cases). The pathogenesis involves tumor-secreted growth factors, such as Transforming Growth Factor-alpha (TGF-α), which stimulate epidermal keratinocytes and fibroblasts. **Analysis of Incorrect Options:** * **A. A skin disorder:** While AN manifests on the skin, it is primarily a cutaneous marker of an underlying systemic condition (metabolic or neoplastic) rather than a primary skin disease. * **C. Senile brain disease:** There is no established clinical association between AN and neurodegenerative or senile brain diseases. * **D. Individuals of African descent:** While AN is more easily visible or prevalent in darker skin phototypes due to increased melanin, it is not "usually" found exclusively in this group, nor does this explain its clinical significance in an elderly patient. **High-Yield Clinical Pearls for NEET-PG:** * **Tripe Palms:** Rugose, velvety thickening of the palms; often occurs alongside malignant AN. If seen alone, it is highly associated with **lung cancer**; if seen with AN, it points to **gastric cancer**. * **Leser-Trélat Sign:** Sudden eruption of multiple seborrheic keratoses; another paraneoplastic sign often associated with internal malignancy and AN. * **Drug-induced AN:** Can be caused by systemic corticosteroids, nicotinic acid, and oral contraceptives.

Q: A 28-year-old pregnant female presents with complaints of brownish pigmentation on the bridge of her nose and cheeks, noticed after returning from a beach vacation. There is no pain or itching at the affected site. What is your most likely diagnosis?

Chloasma. ### Explanation **Diagnosis: Chloasma (Melasma)** The clinical presentation of symmetric, asymptomatic brownish pigmentation on the bridge of the nose and cheeks (malar distribution) in a pregnant female, exacerbated by sun exposure, is classic for **Chloasma**. 1. **Why Chloasma is correct:** Also known as the "mask of pregnancy," Chloasma is an acquired hypermelanosis. It is driven by hormonal changes (increased estrogen, progesterone, and MSH) and triggered by UV radiation. The absence of itching or pain distinguishes it from inflammatory conditions. 2. **Why other options are incorrect:** * **Photodermatitis:** This typically presents with inflammatory signs like erythema, itching, or scaling following sun exposure, rather than isolated hyperpigmentation. * **Systemic Lupus Erythematosus (SLE):** While SLE features a malar "butterfly" rash, it is typically an erythematous (red), often raised rash that spares the nasolabial folds and is usually accompanied by systemic symptoms (fever, joint pain). * **Acne Rosacea:** This presents with erythema, telangiectasia, papules, and pustules. It is a vascular and inflammatory disorder, not a primary pigmentary one. **High-Yield Clinical Pearls for NEET-PG:** * **Patterns:** Melasma has three clinical patterns: Centrofacial (most common), Malar, and Mandibular. * **Wood’s Lamp Examination:** Used to determine the depth of pigment. **Epidermal** type shows enhancement under Wood's lamp (responds best to treatment), while **Dermal** type does not enhance. * **Treatment:** The gold standard is **Kligman’s Formula** (Triple Combination Therapy): Hydroquinone (lightening agent), Tretinoin (exfoliant), and a Corticosteroid (anti-inflammatory). * **Prevention:** Strict photoprotection (broad-spectrum sunscreens) is the most critical step in management.

Q: Cafe au lait macules are seen in which of the following conditions?

All of the above. **Explanation:** Cafe au lait macules (CALMs) are well-circumscribed, hyperpigmented, light-brown macules or patches caused by an increased concentration of melanin within the epidermis (melanocytes and keratinocytes). While they can occur sporadically in the general population, multiple CALMs are a hallmark of several multisystem genetic disorders. * **Neurofibromatosis Type 1 (NF-1):** This is the most common association. According to the NIH diagnostic criteria, **6 or more CALMs** (measuring >5 mm in prepubertal and >15 mm in postpubertal individuals) are required for diagnosis. They are typically "Coast of California" (smooth) borders. * **McCune-Albright Syndrome:** Characterized by the triad of polyostotic fibrous dysplasia, precocious puberty, and CALMs. These macules are often large, unilateral, and have irregular "Coast of Maine" borders. * **Bloom Syndrome:** An autosomal recessive chromosomal instability disorder characterized by short stature, photosensitivity, and telangiectatic erythema. CALMs are a recognized cutaneous feature of this syndrome. **Clinical Pearls for NEET-PG:** 1. **Coast of California vs. Maine:** Smooth borders (NF-1) vs. Irregular/jagged borders (McCune-Albright). 2. **Crowe’s Sign:** Axillary or inguinal freckling, a pathognomonic sign for NF-1. 3. **Other Associations:** CALMs are also seen in **Legius Syndrome** (SPRED1 mutation), **Fanconi Anemia**, **Tuberous Sclerosis** (rarely), and **Ataxia-telangiectasia**. 4. **Histology:** Increased melanin in the basal layer; giant melanosomes (macromelanosomes) are specifically seen in NF-1.

Q: Which of the following conditions presents with hypopigmentation?

Pityriasis versicolor. The key to answering this question lies in distinguishing between **hypopigmentation** (reduced melanin) and **depigmentation** (total loss of melanin). ### **Explanation of the Correct Answer** **B. Pityriasis versicolor:** This is a superficial fungal infection caused by the yeast *Malassezia furfur*. The organism produces **azelaic acid**, which competitively inhibits tyrosinase (the enzyme responsible for melanin synthesis). This leads to a reduction in melanin production, resulting in **hypopigmented** macules with fine scaling (branny desquamation). ### **Analysis of Incorrect Options** * **A. Vitiligo:** This is characterized by **depigmentation**, not hypopigmentation. It involves the complete autoimmune destruction of melanocytes, resulting in "milky white" patches. * **C. Lichen planus:** This typically presents as "purple, polygonal, pruritic, planar papules." It often leads to **post-inflammatory hyperpigmentation** (darkening) due to pigmentary incontinence. * **D. Melasma:** This is a common acquired **hyperpigmentation** disorder, usually appearing as symmetrical brown patches on the face, often associated with UV exposure and hormonal changes (pregnancy/OCPs). ### **NEET-PG High-Yield Pearls** * **Wood’s Lamp:** Pityriasis versicolor shows a characteristic **yellowish-gold (coppery)** fluorescence. * **Microscopy:** KOH mount reveals the classic **"Spaghetti and Meatballs"** appearance (hyphae and spores). * **Sign:** **Besnier’s sign** (or Scratch sign) is positive in Pityriasis versicolor—scaling becomes more apparent upon scratching the lesion. * **Treatment:** Topical antifungals (Ketoconazole shampoo) are first-line; oral Fluconazole/Itraconazole for extensive cases.

Question 1

A female presents with hypopigmented lesions on the central forehead. Which drug is responsible?

Accepted Answer

Para tertiary butyl phenol

Answer

Hydroquinone

Answer

Ether metabolite of hydroquinone

Answer

Para tertiary butyl catechol

Question 2

Vitiligo is commonly associated with which of the following conditions?

Accepted Answer

Diabetes mellitus

Answer

Celiac sprue

Answer

Polycystic ovarian disease

Answer

Alpha-1 antitrypsin deficiency

Question 3

A large, dark brown patch is noted on the back. What is the most likely diagnosis?

Accepted Answer

Becker nevus

Answer

Seborrheic melanosis

Answer

Lichen planus pigmentosus

Answer

Pityriasis versicolor

Question 4

Which of the following conditions are associated with acanthosis nigricans?

Accepted Answer

Carcinoma of the stomach, Obesity, and Insulin resistance

Answer

Carcinoma of the stomach only

Answer

Hemochromatosis only

Answer

Obesity, Insulin resistance, and Hemochromatosis

Question 5

Which is the characteristic lesion of pregnancy?

Accepted Answer

Chloasma

Answer

Vitiligo

Answer

Pemphigus

Answer

Tinea

Question 6

In an elderly patient, acanthosis nigricans usually indicates what?

Accepted Answer

Malignancy

Answer

A skin disorder

Answer

Senile brain disease

Answer

It is usually found in individuals of African descent

Question 7

What is the best treatment for vitiligo of the vulva?

Accepted Answer

PUVA therapy

Answer

Corticosteroids

Answer

Coal tar

Answer

All of the above

Question 8

A 28-year-old pregnant female presents with complaints of brownish pigmentation on the bridge of her nose and cheeks, noticed after returning from a beach vacation. There is no pain or itching at the affected site. What is your most likely diagnosis?

Accepted Answer

Chloasma

Answer

Photodermatitis

Answer

Systemic Lupus Erythematosus (SLE)

Answer

Acne rosacea

Question 9

Cafe au lait macules are seen in which of the following conditions?

Accepted Answer

All of the above

Answer

Neurofibromatosis

Answer

Albright syndrome

Answer

Bloom syndrome

Question 10

Which of the following conditions presents with hypopigmentation?

Accepted Answer

Pityriasis versicolor

Answer

Vitiligo

Answer

Lichen planus

Answer

Melasma

Pigmentary Disorders — MCQs

Pigmentary Disorders — MCQs

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