Pigmentary Disorders Practice Questions

Q: Which of the following is an X-linked dominant condition presenting as hyperpigmented lesions along lines of Blaschko?

Incontinentia pigmenti. **Explanation:** **Incontinentia Pigmenti (IP)**, also known as Bloch-Sulzberger syndrome, is an **X-linked dominant** genodermatosis caused by a mutation in the **IKBKG (NEMO) gene**. It is typically lethal in males in utero. The skin lesions characteristically follow the **Lines of Blaschko**, reflecting functional mosaicism due to X-inactivation (Lyonization). IP progresses through four distinct clinical stages: 1. **Vesicular stage:** Linear vesicles (present at birth/infancy). 2. **Verrucous stage:** Hyperkeratotic warty plaques. 3. **Hyperpigmented stage:** Swirl-like or "splashed paint" hyperpigmentation along Blaschko lines (the stage described in the question). 4. **Atrophic/Hypopigmented stage:** Linear dermal atrophy. **Why other options are incorrect:** * **Hypomelanosis of Ito:** Presents as **hypopigmented** (not hyperpigmented) whorls along the lines of Blaschko. It is often referred to as the "negative" of IP. * **LEOPARD syndrome:** An autosomal dominant condition (RASopathy) characterized by multiple lentigines (scattered, not along Blaschko lines), ECG conduction defects, Ocular hypertelorism, Pulmonic stenosis, Abnormal genitalia, Retardation of growth, and Deafness. * **Pseudoxanthoma elasticum:** An autosomal recessive disorder of connective tissue (ABCC6 gene) presenting with "plucked chicken skin" appearance on flexures and angioid streaks in the retina. **High-Yield Clinical Pearls for NEET-PG:** * **Histology of IP:** Characterized by "pigmentary incontinence" (melanin dropping into the dermis) and eosinophilic spongiosis in the first stage. * **Associated findings:** Peg-shaped teeth (hypodontia), cicatricial alopecia, and CNS/ocular abnormalities. * **Inheritance:** If a question mentions "X-linked dominant" and "lethal in males," IP should be your first thought.

Q: In a patch of vitiligo, what is the primary histological finding regarding melanocytes?

Melanocytes are absent. **Explanation:** **Vitiligo** is an acquired, chronic pigmentary disorder characterized by the selective destruction of melanocytes. **1. Why the correct answer is right:** The hallmark of vitiligo is the **complete absence of functional melanocytes** in the epidermis of the affected skin. This is primarily due to an autoimmune-mediated destruction where cytotoxic T-cells target melanocyte antigens. Histologically, when a biopsy is taken from a stable vitiligo patch and stained with specialized stains (like Fontana-Masson or immunohistochemistry using MART-1/HMB-45), there is a total lack of melanocytes and melanin pigment in the basal layer. **2. Why the incorrect options are wrong:** * **Option A & B:** These describe functional or structural defects (like in Albinism or Chédiak-Higashi syndrome) where melanocytes are present but fail to produce or transfer melanin. In vitiligo, the "factory" (melanocyte) itself is destroyed, not just the "product" (melanin). * **Option D:** A "reduction" in melanocytes is characteristic of **Pityriasis alba** or **Post-inflammatory hypopigmentation**. In vitiligo, the loss is absolute in the depigmented patch. **3. High-Yield Clinical Pearls for NEET-PG:** * **Wood’s Lamp:** Vitiligo shows a characteristic **"milky-white" fluorescence**. * **Koebner Phenomenon:** Development of vitiligo at sites of trauma (Common in Type B/Generalized vitiligo). * **Leucotrichia:** Presence of white hair within a vitiligo patch. It indicates the destruction of the melanocyte reservoir in the hair follicle and suggests a poor prognosis for medical repigmentation. * **Associated Conditions:** Most commonly associated with **Autoimmune Thyroiditis** (Hashimoto's).

Q: A 5-year-old boy presents with recurrent, multiple, asymptomatic, oval and circular, faintly hypopigmented macules with fine scaling on his face. What is the most probable clinical diagnosis?

Pityriasis alba. ### Explanation **Pityriasis alba** is the most probable diagnosis based on the classic clinical triad: **faintly hypopigmented macules**, **fine scaling**, and occurrence in a **child** (usually 3–16 years old). It is considered a minor feature of atopic dermatitis. The lesions are typically asymptomatic and most commonly involve the face (cheeks). The scaling is more prominent in winter, while the hypopigmentation becomes more noticeable in summer due to tanning of the surrounding skin. **Why other options are incorrect:** * **Pityriasis versicolor:** Caused by *Malassezia furfur*, it typically affects the trunk (seborrheic areas) in young adults. While it presents with fine scales (Cheadle’s/V-sign), facial involvement is rare in children unless they are immunocompromised. * **Indeterminate leprosy:** Presents as a single or few hypopigmented macules with **loss of sensation** or hair. It lacks the fine "powdery" scaling characteristic of Pityriasis alba. * **Acrofacial vitiligo:** Characterized by **depigmented** (chalky white) macules rather than hypopigmented ones. Vitiligo has well-defined borders, no scaling, and typically involves periorificial areas (mouth, eyes) and fingertips. **High-Yield Clinical Pearls for NEET-PG:** * **Etiology:** Often associated with **Atopy** and xerosis. * **Histopathology:** Shows hyperkeratosis, parakeratosis, and decreased melanin in the basal layer. * **Treatment:** Reassurance, emollients, and sun protection. Low-potency topical steroids or calcineurin inhibitors (Tacrolimus) may be used for inflammation. * **Differentiating Scale:** Pityriasis alba has fine, adherent scales; Pityriasis versicolor has "branny" (furfuraceous) scales visible on scraping.

Q: A female presents with a hypopigmented lesion on the center of her forehead. What drug is responsible?

Para tertiary butylphenol. ### Explanation The clinical presentation describes **Chemical Leucoderma** (contact depigmentation). The forehead is a classic site for this condition due to the use of **bindis** or adhesive tapes. **Why Para-tertiary butylphenol (PTBP) is correct:** PTBP is a phenolic compound commonly used as an adhesive in bindis, watch straps, and footwear. It is structurally similar to **tyrosine**, the precursor of melanin. PTBP acts as a melanocytotoxic agent by competing with tyrosine for the enzyme tyrosinase, leading to the selective destruction of melanocytes and subsequent depigmentation. In India, "Bindi-mark depigmentation" on the forehead is the most common presentation of PTBP-induced leucoderma. **Analysis of Incorrect Options:** * **Hydroquinone (A):** Used therapeutically to treat hyperpigmentation (melasma). While it inhibits tyrosinase, it rarely causes permanent depigmentation unless used in very high concentrations (causing "confetti-like" depigmentation). * **Ether metabolite of hydroquinone (B):** Specifically, Monobenzyl ether of hydroquinone (MBEH) is a potent depigmenting agent, but it is typically used to permanently depigment remaining skin in universal vitiligo, not found in bindi adhesives. * **Para-tertiary butyl catechol (C):** This is a related phenolic compound found in hair dyes and rubber chemicals, but PTBP is the specific culprit associated with bindi adhesives and forehead lesions. **High-Yield Clinical Pearls for NEET-PG:** * **Common Culprits:** PTBP (bindis/adhesives), Monobenzyl ether of hydroquinone (rubber gloves/condoms), and PPD (hair dyes). * **Distinguishing Feature:** Unlike Vitiligo, chemical leucoderma usually lacks the "Koebner phenomenon" and is localized to the site of contact. * **Occupational Link:** Often seen in workers in the rubber, plastic, and leather industries.

Q: A lady presented with complaints of a bluish lesion over the left side of her forehead and left eye, showing an irregular bluish lesion in the left superior conjunctiva and forehead. What is the diagnosis?

Nevus of Ota. **Explanation:** The clinical presentation of a unilateral, bluish-grey hyperpigmented macule involving the forehead and the conjunctiva is classic for **Nevus of Ota** (Oculodermal Melanocytosis). **1. Why Nevus of Ota is correct:** Nevus of Ota is a dermal melanocytosis caused by the failure of melanocytes to migrate from the neural crest to the epidermis, leaving them trapped in the dermis. It typically follows the distribution of the **ophthalmic (V1) and maxillary (V2) branches of the trigeminal nerve**. Involvement of the ocular structures (sclera, conjunctiva, or uvea) is a hallmark feature that distinguishes it from other dermal melanocytoses. **2. Why other options are incorrect:** * **Nevus of Ito:** Similar to Nevus of Ota histologically, but it involves the **acromioclavicular region** (shoulder, side of the neck, or scapular area) rather than the face. * **Becker’s Nevus:** This is a hamartoma characterized by a brown, hairy (hypertrichotic) patch, usually on the shoulder or chest of adolescent males. It is not bluish and does not involve the eye. * **Mongolian Spot:** These are congenital bluish-grey patches typically found in the **lumbosacral region**. They usually disappear by early childhood, unlike Nevus of Ota, which is permanent and may darken over time. **High-Yield Clinical Pearls for NEET-PG:** * **Gender Predilection:** More common in females and Asians. * **Bilateralism:** Usually unilateral; bilateral cases are rare (5-10%). * **Complication:** The most serious associated risk is **Glaucoma** (increased intraocular pressure) and, rarely, **Malignant Melanoma** (uveal or leptomeningeal). * **Treatment of Choice:** **Q-switched Nd:YAG laser** (1064 nm) is the gold standard for removing the dermal pigment.

Q: A 69-year-old woman develops dark, velvety pigmentation in her axillae. She has noticed 10 lb weight loss over the past 3 months with heartburn and early satiety. She notices no other symptoms. Which of the following conditions should be investigated?

A visceral carcinoma. **Explanation:** The clinical presentation describes **Acanthosis Nigricans (AN)**, characterized by dark, velvety, hyperpigmented plaques in intertriginous areas like the axillae and neck. While AN is most commonly associated with insulin resistance, the presence of **"red flag" symptoms**—advanced age (69 years), rapid onset, and systemic signs (10 lb weight loss, early satiety, heartburn)—strongly points toward **Malignant Acanthosis Nigricans**. 1. **Why A is correct:** Malignant AN is a paraneoplastic syndrome. In approximately 90% of cases, it is associated with an intra-abdominal malignancy, most commonly **Gastric Adenocarcinoma** (explaining the patient's heartburn and early satiety). Unlike the benign form, malignant AN often appears suddenly, spreads rapidly, and involves the mucosa or palms (tripe palms). 2. **Why B is incorrect:** While lymphomas can cause paraneoplastic skin changes (like exfoliative dermatitis or Ichthyosis acquisita), they are not the classic association for Acanthosis Nigricans. 3. **Why C is incorrect:** Diabetes mellitus and obesity are the most common causes of *Benign* AN (Type II). However, they do not typically present with rapid weight loss or gastric symptoms in an elderly patient. 4. **Why D is incorrect:** Sarcoidosis typically presents with skin findings like Lupus Pernio or erythema nodosum, not velvety hyperpigmentation. **NEET-PG High-Yield Pearls:** * **Most common site for AN:** Posterior neck, followed by axillae. * **Most common malignancy associated:** Gastric Adenocarcinoma (TGF-alpha produced by the tumor is the implicated growth factor). * **Tripe Palms:** Velvety thickening of palmar skin; if seen with AN, it highly suggests internal malignancy (Lung or Gastric). * **Leser-Trélat Sign:** Sudden eruption of multiple seborrheic keratoses; also a paraneoplastic sign often seen alongside malignant AN.

Q: A patient presenting with brownish pigmentation and normal laboratory findings may be suffering from which condition?

Neurofibromatosis. ### Explanation **Correct Option: C. Neurofibromatosis** Neurofibromatosis Type 1 (NF-1), or von Recklinghausen’s disease, is a multisystem genetic disorder characterized by cutaneous pigmentary changes. The hallmark finding is **Café-au-lait macules (CALMs)**—well-demarcated, brownish "coffee with milk" spots. These are caused by increased melanin content in the epidermis and giant melanosomes (macromelanosomes). Crucially, NF-1 is a clinical diagnosis; unless there is specific systemic involvement (like pheochromocytoma), routine **laboratory findings (blood counts, electrolytes, hormones) are typically normal.** **Why other options are incorrect:** * **A. Addison’s Disease:** While it causes diffuse hyperpigmentation (bronzing), it is characterized by **abnormal laboratory findings**, specifically low serum cortisol, high ACTH, hyponatremia, and hyperkalemia. * **B. Fibrous Dysplasia:** Specifically in McCune-Albright Syndrome, patients present with CALMs (typically with irregular "Coast of Maine" borders). However, this syndrome is associated with **abnormal laboratory findings** due to endocrinopathies (e.g., precocious puberty, hyperthyroidism, or growth hormone excess). **NEET-PG High-Yield Pearls:** * **Crowe’s Sign:** Axillary or inguinal freckling; a pathognomonic sign for NF-1. * **Lisch Nodules:** Iris hamartomas seen on slit-lamp exam (most common ocular finding). * **CALM Borders:** NF-1 spots have smooth "Coast of California" borders, whereas McCune-Albright spots have jagged "Coast of Maine" borders. * **Diagnostic Criteria:** 6 or more CALMs (>5mm in prepubertal, >15mm in postpubertal) are required for NF-1 diagnosis.

Q: Which of the following conditions is NOT typically associated with hyperpigmentation?

Hypothyroidism (Myxedema). **Explanation:** The correct answer is **Hypothyroidism (Myxedema)**. In hypothyroidism, the skin is typically characterized by **pallor** (due to dermal mucin and edema) and a yellowish tint (carotenemia), rather than hyperpigmentation. **Why Hypothyroidism is the correct answer:** Hypothyroidism leads to a decrease in metabolic rate. The skin becomes cool, dry, and pale. While **carotenemia** (yellowish discoloration of palms and soles) occurs due to reduced conversion of beta-carotene to Vitamin A, generalized hyperpigmentation is not a feature. **Analysis of Incorrect Options:** * **Addison’s Disease:** Primary adrenal insufficiency leads to high levels of **ACTH**. Since ACTH and Melanocyte-Stimulating Hormone (MSH) share a common precursor (**POMC**), excess ACTH cross-reacts with MC1R receptors, causing diffuse hyperpigmentation, especially in skin creases, scars, and buccal mucosa. * **Cushing’s Disease:** Specifically refers to a pituitary adenoma secreting excess **ACTH**. Similar to Addison’s, the high ACTH levels lead to hyperpigmentation. (Note: Cushing’s *Syndrome* due to adrenal tumors or exogenous steroids usually lacks hyperpigmentation because ACTH is suppressed). * **Graves’ Disease:** Hyperthyroidism is associated with generalized hyperpigmentation in about 10% of cases. It is thought to be due to increased release of ACTH (compensatory to rapid cortisol metabolism) or direct stimulation of melanocytes by thyroid hormones. **NEET-PG High-Yield Pearls:** * **Flag Sign:** Alternating bands of light and dark hair seen in Kwashiorkor (nutritional hyperpigmentation). * **Acanthosis Nigricans:** Velvety hyperpigmentation associated with Insulin Resistance and Gastric Adenocarcinoma. * **Vitamin B12 Deficiency:** A common cause of megaloblastic anemia that presents with knuckle hyperpigmentation.

Q: Yellowish discoloration of oral mucous membrane, skin, and sclera of the eye is characteristic of which condition?

Carotenemia. **Explanation:** **Correct Answer: D. Carotenemia** Carotenemia is caused by the excessive intake of carotenoid-rich foods (like carrots, oranges, and squash), leading to high serum levels of beta-carotene. This lipid-soluble pigment deposits in the **stratum corneum**. Clinically, it presents as a yellowish-orange discoloration most prominent on the palms, soles, and nasolabial folds. **Crucial Distinction:** While carotenemia involves the skin and can affect the oral mucosa, it **spares the sclera**. This is the key clinical differentiator from jaundice (icterus), where bilirubin has a high affinity for the elastin-rich sclera. *(Note: The question mentions sclera; however, in the context of the given options, Carotenemia is the most relevant dermatological condition associated with yellow skin discoloration, though classic teaching emphasizes scleral sparing.)* **Why other options are incorrect:** * **Pernicious Anemia:** Typically presents with "lemon-yellow" pallor due to a combination of anemia and mild hemolysis, but it is not a primary pigmentary deposition. * **Sickle Cell Anemia:** May cause jaundice (yellowing of sclera and skin) due to indirect hyperbilirubinemia from chronic hemolysis, but it is not described as a primary "discoloration" therapy or condition in this context. * **Chloramphenicol Therapy:** Classically associated with **"Gray Baby Syndrome"** in neonates, characterized by ashen-gray cyanosis, not yellowing. **High-Yield NEET-PG Pearls:** * **Lycopenemia:** A variant of carotenemia caused by excessive tomato intake; results in a deeper orange-red skin hue. * **Scleral Icterus:** Occurs when serum bilirubin exceeds **2–2.5 mg/dL**. * **Quinacrine/Mepacrine:** An antimalarial drug that can also cause generalized yellow skin discoloration and scleral yellowing.

Q: A 28-year-old female presents with a rash. Which of the following conditions is NOT associated with an increased risk of developing this rash?

Niacin deficiency. ***Niacin deficiency*** - **Niacin deficiency** causes **pellagra**, characterized by the "4 D's": dermatitis, diarrhea, dementia, and death - not acanthosis nigricans. - High-dose **niacin therapy** (not deficiency) can occasionally cause acanthosis nigricans as a side effect. *Internal malignancy* - **Gastric adenocarcinoma** is the most common malignancy associated with **paraneoplastic acanthosis nigricans**. - The rash may appear suddenly and be more extensive, often involving **mucosal surfaces** like the oral cavity. *Polycystic Ovarian Disease (PCOD)* - **Insulin resistance** in PCOD leads to hyperinsulinemia, which stimulates **insulin-like growth factor-1 (IGF-1) receptors**. - This causes **keratinocyte proliferation** and the characteristic velvety, hyperpigmented plaques of acanthosis nigricans. *Diabetes mellitus* - **Type 2 diabetes** with insulin resistance commonly presents with acanthosis nigricans, especially in **skin folds**. - The condition often improves with **glycemic control** and weight reduction, indicating its metabolic association.

Question 1

Which of the following is an X-linked dominant condition presenting as hyperpigmented lesions along lines of Blaschko?

Accepted Answer

Incontinentia pigmenti

Answer

Hypomelanosis of Ito

Answer

LEOPARD syndrome

Answer

Pseudoxanthoma elasticum

Question 2

In a patch of vitiligo, what is the primary histological finding regarding melanocytes?

Accepted Answer

Melanocytes are absent

Answer

Melanin synthesis is inhibited

Answer

Melanosomes are absent

Answer

Melanocytes are reduced

Question 3

A 5-year-old boy presents with recurrent, multiple, asymptomatic, oval and circular, faintly hypopigmented macules with fine scaling on his face. What is the most probable clinical diagnosis?

Accepted Answer

Pityriasis alba

Answer

Pityriasis versicolor

Answer

Indeterminate leprosy

Answer

Acrofacial vitiligo

Question 4

A female presents with a hypopigmented lesion on the center of her forehead. What drug is responsible?

Accepted Answer

Para tertiary butylphenol

Answer

Hydroquinone

Answer

Ether metabolite of hydroquinone

Answer

Para tertiary butyl catechol

Question 5

A lady presented with complaints of a bluish lesion over the left side of her forehead and left eye, showing an irregular bluish lesion in the left superior conjunctiva and forehead. What is the diagnosis?

Accepted Answer

Nevus of Ota

Answer

Nevus of Ito

Answer

Becker's nevus

Answer

Mongolian spot

Question 6

A 69-year-old woman develops dark, velvety pigmentation in her axillae. She has noticed 10 lb weight loss over the past 3 months with heartburn and early satiety. She notices no other symptoms. Which of the following conditions should be investigated?

Accepted Answer

A visceral carcinoma

Answer

Lymphoma

Answer

Diabetes mellitus

Answer

Sarcoidosis

Question 7

A patient presenting with brownish pigmentation and normal laboratory findings may be suffering from which condition?

Accepted Answer

Neurofibromatosis

Answer

Addison's disease

Answer

Fibrous dysplasia

Answer

None of the above

Question 8

Which of the following conditions is NOT typically associated with hyperpigmentation?

Accepted Answer

Hypothyroidism (Myxedema)

Answer

Addison's disease

Answer

Cushing's disease

Answer

Graves disease

Question 9

Yellowish discoloration of oral mucous membrane, skin, and sclera of the eye is characteristic of which condition?

Accepted Answer

Carotenemia

Answer

Pernicious anemia

Answer

Sickle cell anemia

Answer

Chloramphenicol therapy

Question 10

A 28-year-old female presents with a rash. Which of the following conditions is NOT associated with an increased risk of developing this rash?

Accepted Answer

Niacin deficiency

Answer

Internal malignancy

Answer

Polycystic Ovarian Disease (PCOD)

Answer

Diabetes mellitus

Pigmentary Disorders — MCQs

Pigmentary Disorders — MCQs

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