Basic Dermatology Practice Questions

Q: The pustular, neutrophil-rich skin lesions that develop or worsen following intradermal trauma is called what?

Pathergy. **Explanation:** The correct answer is **Pathergy**. **1. Why Pathergy is Correct:** Pathergy refers to an exaggerated skin inflammatory response to minor trauma (such as a needle prick). Clinically, it manifests as the development of a papule or sterile pustule 24–48 hours after an intradermal insult. Histologically, these lesions are characterized by a dense **neutrophilic infiltrate**. This phenomenon is a hallmark diagnostic criterion for **Behçet’s disease** and is also frequently observed in **Pyoderma gangrenosum** and Sweet syndrome. **2. Why Other Options are Incorrect:** * **Erythema nodosum (A):** This is a form of septal panniculitis presenting as tender, erythematous nodules, typically on the shins. It is a hypersensitivity reaction but is not triggered by intradermal trauma. * **Koebner Phenomenon (B):** Also known as the "isomorphic response," this refers to the development of **new lesions of a pre-existing dermatosis** (like Psoriasis, Vitiligo, or Lichen Planus) at the site of trauma. Unlike pathergy, it does not specifically result in a sterile pustule and takes longer (7–14 days) to appear. * **Dermatitis herpetiformis (D):** This is an autoimmune blistering disorder associated with Celiac disease, characterized by intensely pruritic vesicles on extensor surfaces and IgA deposits in dermal papillae. It is not trauma-induced. **Clinical Pearls for NEET-PG:** * **Pathergy Test:** Performed using a 20-gauge needle; positive if a >2mm indurated papule/pustule forms. * **Differential Diagnosis:** While Pathergy = Behçet’s/Pyoderma gangrenosum, **Pseudo-pathergy** can be seen in Sweet syndrome. * **High-Yield Distinction:** Koebner = "Same lesion as disease" (e.g., scale in Psoriasis); Pathergy = "Sterile pustule/hyper-reactivity."

Q: Oral examination of a 57-year-old female reveals a white patch on the buccal mucosa that cannot be scraped off. She has no features suggestive of immunosuppression. What is the most likely diagnosis?

Leukoplakia. **Explanation:** The clinical presentation of a **white patch on the buccal mucosa that cannot be scraped off** in an immunocompetent patient is the classic definition of **Leukoplakia**. 1. **Why Leukoplakia is correct:** According to the WHO, leukoplakia is a clinical term for a white patch or plaque that cannot be characterized clinically or pathologically as any other disease. The key diagnostic feature is that it is **non-scrapable**, distinguishing it from pseudomembranous candidiasis. It is considered a **premalignant (potentially malignant) condition**, often associated with tobacco use or chronic irritation. 2. **Why other options are incorrect:** * **Hairy Leukoplakia:** This is caused by the **Epstein-Barr Virus (EBV)** and typically presents as white, corrugated (shaggy) patches on the **lateral borders of the tongue**. It is almost exclusively seen in **immunocompromised** patients (e.g., HIV/AIDS). * **Erythroplakia:** This presents as a **fiery red patch** that cannot be characterized as any other condition. While it has a much higher risk of malignant transformation than leukoplakia, it does not present as a white patch. * **Thrush (Oral Candidiasis):** This presents as creamy white "curd-like" patches. Unlike leukoplakia, these patches **can be easily scraped off** with a tongue depressor, often leaving an erythematous, bleeding base. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site:** Buccal mucosa and floor of the mouth. * **Malignant Transformation:** The "speckled" variety (Erythroleukoplakia) has a higher risk of turning into Squamous Cell Carcinoma (SCC) than the homogenous type. * **Biopsy Rule:** Any white patch persisting for more than 2-3 weeks after removing local irritants must be biopsied to rule out dysplasia or malignancy.

Q: The given condition is caused due to deficiency of which of the following?

Zinc. ***Zinc*** - **Acrodermatitis enteropathica** is the pathognomonic skin manifestation of **zinc deficiency**, presenting with perioral, perianal, and acral dermatitis. - Zinc is essential for **wound healing**, **immune function**, and maintaining skin integrity, particularly in rapidly dividing cells. *Niacin* - **Niacin deficiency** causes **pellagra** with the "4 Ds": dermatitis, diarrhea, dementia, and death. - The dermatitis in pellagra typically presents as **photosensitive** skin lesions in sun-exposed areas, not the perioral/perianal pattern seen here. *Iron* - **Iron deficiency** primarily causes **microcytic anemia** with symptoms like fatigue, pallor, and koilonychia (spoon nails). - Iron deficiency does not typically cause the characteristic **acrodermatitis enteropathica** skin pattern observed in this condition. *Selenium* - **Selenium deficiency** can cause **Keshan disease** (cardiomyopathy) and **Kashin-Beck disease** (osteoarthropathy). - Selenium deficiency does not produce the distinctive **perioral and perianal dermatitis** that characterizes zinc deficiency.

Q: Saw tooth rete pegs are seen in which of the following conditions?

Lichen planus. **Explanation:** **Lichen Planus (Option A)** is the correct answer. The characteristic histopathological hallmark of Lichen Planus is a **"saw-tooth" appearance of the rete pegs**. This occurs due to a dense, band-like lymphocytic infiltrate at the dermo-epidermal junction (interface dermatitis) that causes liquefactive degeneration of the basal cell layer. As the basal layer is destroyed, the epidermis compensates and remodels, leading to the pointed, triangular elongation of the rete ridges resembling the teeth of a saw. **Analysis of Incorrect Options:** * **Leukoplakia (Option B):** This is a clinical term for a white patch. Histologically, it shows hyperkeratosis and epithelial dysplasia, but not the specific saw-tooth pattern. * **Pemphigus Vulgaris (Option C):** This is an autoimmune blistering disease characterized by **acantholysis** (loss of intercellular connections). Key histological features include "row of tombstones" (intact basal layer) and intraepidermal suprabasal blisters. * **Psoriasis (Option D):** Psoriasis features regular elongation of rete ridges, often described as **"test-tube in a rack"** appearance, along with Munro’s microabscesses and Kogoj’s pustules. **High-Yield Clinical Pearls for NEET-PG:** * **Max Joseph Spaces:** Small areas of separation between the epidermis and dermis seen in Lichen Planus. * **Civatte Bodies (Colloid bodies):** Shrunken, eosinophilic apoptotic keratinocytes found in the lower epidermis/upper dermis of Lichen Planus patients. * **Wickham Striae:** The clinical manifestation of hypergranulosis seen as white lacy patterns on the surface of papules or oral mucosa. * **6 P’s of Lichen Planus:** Planar (flat-topped), Purple, Polygonal, Pruritic, Papules, and Plaques.

Q: Angioid streaks in the eyes are seen in which of the following conditions?

Pseudoxanthoma elasticum. **Explanation:** **Pseudoxanthoma Elasticum (PXE)** is the correct answer. It is a multisystem genetic disorder characterized by the progressive calcification and fragmentation of elastic fibers in the skin, eyes, and cardiovascular system. 1. **Why it is correct:** In the eyes, calcification of the elastic lamina of **Bruch’s membrane** leads to cracks or dehiscence. On fundoscopy, these appear as dark, reddish-brown, jagged lines radiating from the optic disc, known as **Angioid Streaks**. Cutaneously, PXE presents as yellowish papules on the neck and flexures, giving a "plucked chicken skin" appearance. 2. **Why other options are incorrect:** * **Tendinous xanthoma:** These are lipid deposits in tendons (commonly the Achilles tendon), typically associated with Familial Hypercholesterolemia. * **Xanthelasma:** These are yellowish plaques on the eyelids caused by localized lipid deposits. While they occur near the eye, they do not involve Bruch's membrane or cause angioid streaks. * **Eruptive xanthoma:** These are small, itchy, yellow-red papules appearing suddenly on extensor surfaces, usually due to severe hypertriglyceridemia. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Angioid Streaks (PEPSI):** **P**seudoxanthoma elasticum, **E**hlers-Danlos syndrome, **P**aget’s disease of bone, **S**ickle cell anemia (and other hemoglobinopathies), **I**diopathic. * **Inheritance of PXE:** Most commonly Autosomal Recessive (ABCC6 gene mutation). * **Systemic Involvement:** Patients are at high risk for premature atherosclerosis, intermittent claudication, and gastrointestinal hemorrhage.

Q: A 12-year-old girl presents for a routine physical examination. The patient has numerous freckles over her upper trunk and face. Which of the following terms best describes the morphologic appearance of her freckles?

Macule. **Explanation:** The correct answer is **Macule**. **1. Why Macule is Correct:** A **macule** is defined as a flat, circumscribed area of altered skin color that is less than 1 cm in diameter. It is not palpable (you cannot feel it with your eyes closed) because there is no elevation or depression relative to the surrounding skin. Freckles (ephelides) are classic examples of macules; they represent small areas of increased melanin pigment without an increase in the number of melanocytes. **2. Why Other Options are Incorrect:** * **Comedo (A):** This is a primary lesion of acne. It is a "plug" of keratin and sebum within a hair follicle. It can be open (blackhead) or closed (whitehead). * **Nodule (C):** A nodule is a solid, palpable, circumscribed elevation that is larger than 1 cm in diameter and often has a significant dermal or subcutaneous component. * **Papule (D):** A papule is a solid, elevated, palpable lesion that is less than 1 cm in diameter. Unlike a macule, a papule has a distinct vertical dimension. **3. Clinical Pearls for NEET-PG:** * **Macule vs. Patch:** A flat lesion 1 cm, it is called a **patch** (e.g., Vitiligo). * **Papule vs. Plaque:** An elevated lesion 1 cm is a **plaque** (e.g., Psoriasis). * **Freckles (Ephelides):** These darken with sun exposure and are due to increased melanin production. In contrast, **Lentigines** do not darken with sun exposure and are due to a linear hyperplasia of melanocytes. * **Axillary Freckling:** Known as **Crowe’s sign**, this is a high-yield diagnostic feature for Neurofibromatosis Type 1 (NF-1).

Q: A 70-year-old male presented with an asymptomatic white patch on the oral cavity following the application of a denture. What is the treatment of choice?

Ascertaining the denture is fitted properly. ### Explanation **Diagnosis: Frictional Keratosis** The clinical presentation describes **Frictional Keratosis**, a common reactive condition of the oral mucosa. It occurs due to chronic low-grade mechanical irritation—in this case, an ill-fitting denture. This results in hyperkeratosis, appearing as an asymptomatic, non-detachable white patch (leukoplakia-like). **Why Option C is Correct:** The primary management of frictional keratosis is the **removal of the offending stimulus**. If the white patch is caused by mechanical trauma from a denture, ensuring the denture is fitted properly or adjusted will eliminate the friction. In most cases, the lesion will resolve spontaneously once the irritation ceases. **Analysis of Incorrect Options:** * **Option A (Radiotherapy):** This is contraindicated. Frictional keratosis is a benign reactive process, not a malignancy. Radiotherapy would cause unnecessary morbidity and potential malignant transformation. * **Option B (Biopsy of all tissues):** While a biopsy is indicated if a lesion is suspicious for malignancy or fails to resolve after removing the stimulus, it is not the *initial* treatment of choice for a clear case of mechanical irritation. * **Option D (Antibiotics):** Frictional keratosis is a mechanical/hyperkeratotic issue, not an infectious one. Antibiotics have no role in its management. **NEET-PG High-Yield Pearls:** * **Clinical Tip:** Always differentiate frictional keratosis from **Oral Candidiasis** (which scrapes off) and **Oral Leukoplakia** (a premalignant lesion that does not have an obvious mechanical cause). * **Management Rule:** For any white patch with an identifiable local cause, remove the cause and review in **2–4 weeks**. If the lesion persists, a biopsy is mandatory to rule out dysplasia or squamous cell carcinoma. * **Common Sites:** Buccal mucosa (along the occlusal line/linea alba), lateral tongue, and edentulous ridges.

Q: Which of the following conditions is due to a defect in the normal keratinization of the oral mucosa?

White sponge nevus. **Explanation:** **White Sponge Nevus (WSN)** is the correct answer because it is a rare, autosomal dominant hereditary condition caused by mutations in the genes encoding **Keratin 4 and Keratin 13**. These keratins are specifically expressed in the suprabasal layers of non-keratinized stratified squamous epithelium (like the oral mucosa). The mutation leads to a defect in the normal keratinization process, resulting in thick, bilateral, white, "spongy" plaques on the buccal mucosa. Histologically, it is characterized by significant **parakeratosis and intracellular edema** (clear cell change) of the spinous layer. **Analysis of Incorrect Options:** * **Erythema Multiforme:** This is an acute, self-limiting **Type IV hypersensitivity reaction** (often triggered by HSV or drugs). It involves subepithelial or intraepithelial vesiculation and "target lesions," not a primary keratinization defect. * **Incontinentia Pigmenti:** This is an X-linked dominant disorder affecting the skin, teeth, and CNS. It is characterized by a defect in the **IKBKG gene**, leading to melanin incontinence (pigment falling into the dermis), not a primary oral keratinization defect. * **Systemic Sclerosis:** This is an autoimmune connective tissue disorder characterized by **excessive collagen deposition** and fibrosis of the skin and internal organs. Oral manifestations include microstomia and widening of the PDL space, but the underlying pathology is fibrotic, not a keratin defect. **High-Yield Clinical Pearls for NEET-PG:** * **Gene Mutation:** KRT4 and KRT13 (highly specific for WSN). * **Clinical Presentation:** Asymptomatic, white, folded/velvety patches that appear in early childhood and do not disappear when stretched (unlike Leukoedema). * **Differential Diagnosis:** Must be distinguished from **Leukoplakia** (premalignant) and **Candidiasis** (scrapable). WSN is entirely benign and requires no treatment.

Q: Pruritus is not seen in which of the following conditions?

Hyperparathyroidism. **Explanation:** Pruritus (itching) is a common systemic manifestation of various metabolic, endocrine, and hematological disorders. To answer this question, one must distinguish between conditions that cause generalized pruritus and those that do not. **Why Hyperparathyroidism is the correct answer:** Primary hyperparathyroidism is generally **not** associated with pruritus. However, it is a common point of confusion because **Secondary Hyperparathyroidism** (occurring in the context of Chronic Kidney Disease) is a major driver of **Uremic Pruritus**. In secondary cases, elevated parathyroid hormone (PTH) levels lead to mast cell degranulation and calcium-phosphate crystal deposition in the skin, causing itch. In the absence of renal failure (Primary Hyperparathyroidism), these mechanisms are typically absent. **Analysis of Incorrect Options:** * **Hyperthyroidism:** Itching is seen in ~4–11% of patients. It is attributed to increased skin temperature, peripheral vasodilation, and increased kinin activity. * **Polycythemia Rubra Vera (PRV):** A classic NEET-PG favorite. It causes **aquagenic pruritus** (stinging/itching after a warm bath) due to histamine release from increased mast cells and basophils. * **Uraemia:** Chronic Kidney Disease (CKD) is one of the most common systemic causes of pruritus. It is multifactorial, involving uremic toxins, xerosis, and the aforementioned secondary hyperparathyroidism. **Clinical Pearls for NEET-PG:** * **Hypothyroidism** also causes pruritus, primarily due to severe skin dryness (xerosis). * **Iron deficiency anemia** is a well-known hematological cause of generalized pruritus, even before anemia develops. * **Obstructive Jaundice:** Pruritus is a hallmark, caused by the accumulation of bile acids and endogenous opioids. * **Most common systemic cause of pruritus:** Chronic Renal Failure (Uraemia).

Question 1

The pustular, neutrophil-rich skin lesions that develop or worsen following intradermal trauma is called what?

Accepted Answer

Pathergy

Answer

Erythema nodosum

Answer

Koebner Phenomenon

Answer

Dermatitis herpetiformis

Question 2

Oral examination of a 57-year-old female reveals a white patch on the buccal mucosa that cannot be scraped off. She has no features suggestive of immunosuppression. What is the most likely diagnosis?

Accepted Answer

Leukoplakia

Answer

Hairy leukoplakia

Answer

Erythroplakia

Answer

Thrush

Question 3

The given condition is caused due to deficiency of which of the following?

Accepted Answer

Zinc

Answer

Niacin

Answer

Iron

Answer

Selenium

Question 4

Saw tooth rete pegs are seen in which of the following conditions?

Accepted Answer

Lichen planus

Answer

Leukoplakia

Answer

Pemphigus vulgaris

Answer

Psoriasis

Question 5

Angioid streaks in the eyes are seen in which of the following conditions?

Accepted Answer

Pseudoxanthoma elasticum

Answer

Tendinous xanthoma

Answer

Xanthalasma

Answer

Eruptive xanthoma

Question 6

Which of the following is NOT a component of Naxos syndrome?

Accepted Answer

Lipomatous skin

Answer

Wooly hair

Answer

Hyperkeratosis of palms

Answer

Arrhythmogenic right ventricular hypertrophy

Question 7

A 12-year-old girl presents for a routine physical examination. The patient has numerous freckles over her upper trunk and face. Which of the following terms best describes the morphologic appearance of her freckles?

Accepted Answer

Macule

Answer

Comedo

Answer

Nodule

Answer

Papule

Question 8

A 70-year-old male presented with an asymptomatic white patch on the oral cavity following the application of a denture. What is the treatment of choice?

Accepted Answer

Ascertaining the denture is fitted properly

Answer

Low dose radiotherapy

Answer

Biopsy of all tissues

Answer

Antibiotics

Question 9

Which of the following conditions is due to a defect in the normal keratinization of the oral mucosa?

Accepted Answer

White sponge nevus

Answer

Erythema multiforme

Answer

Incontinentia pigmenti

Answer

Systemic sclerosis

Question 10

Pruritus is not seen in which of the following conditions?

Accepted Answer

Hyperparathyroidism

Answer

Hyperthyroidism

Answer

Polycythemia rubra vera

Answer

Uraemia

Basic Dermatology — MCQs

Basic Dermatology — MCQs

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