Basic Dermatology Practice Questions

Q: Which sign is pathognomonic for neurofibromatosis?

Axillary freckling. **Explanation:** **Neurofibromatosis Type 1 (NF1)**, also known as von Recklinghausen disease, is an autosomal dominant multisystem disorder. The correct answer is **Axillary freckling (Crowe sign)** because it is considered highly specific (pathognomonic) for NF1. 1. **Axillary Freckling (Crowe Sign):** These are small, 1–3 mm hyperpigmented macules found in intertriginous areas (axilla or groin). Unlike solar lentigines, they appear in areas not exposed to the sun. Their presence is a hallmark diagnostic criterion for NF1. 2. **Cafe-au-lait macules (CALMs):** While these are often the first sign of NF1, they are **not pathognomonic**. CALMs can be seen in healthy individuals, McCune-Albright syndrome, Fanconi anemia, and Legius syndrome. In NF1, the presence of 6 or more macules (>5mm in prepubertal; >15mm in postpubertal) is required for diagnosis. 3. **Shagreen patch:** This is a connective tissue nevus (leathery plaque) typically found on the lower back. It is a characteristic feature of **Tuberous Sclerosis**, not Neurofibromatosis. **High-Yield Clinical Pearls for NEET-PG:** * **Lisch Nodules:** Iris hamartomas (seen on slit-lamp exam) are the most common ocular finding in NF1. * **Optic Glioma:** The most common CNS tumor associated with NF1. * **Sphenoid Wing Dysplasia:** A classic skeletal deformity in NF1. * **Genetics:** NF1 is caused by a mutation in the *NF1* gene on **Chromosome 17** (encodes Neurofibromin), while NF2 is linked to **Chromosome 22** (encodes Merlin).

Q: What is the primary lesion in lichen planus?

Papule. **Explanation:** The primary lesion in **Lichen Planus (LP)** is classically described by the **"6 Ps"**: **P**lanar (flat-topped), **P**urple (violaceous), **P**olygonal, **P**ruritic, **P**apules, and **P**laques. 1. **Why Papule is Correct:** A papule is a solid, raised lesion less than 1 cm in diameter. In LP, the characteristic lesion is a violaceous, flat-topped papule. These papules often coalesce to form larger **plaques**. The surface of these papules typically shows fine, white, lace-like patterns known as **Wickham striae**, which are a hallmark diagnostic feature. 2. **Why Other Options are Incorrect:** * **Macule:** This is a flat, non-palpable change in skin color. While post-inflammatory hyperpigmentation (macules) is common after LP heals, the active primary lesion is always raised. * **Vesicle/Bullae:** These are fluid-filled blisters (vesicles 0.5 cm). While a rare variant called "Bullous Lichen Planus" exists, these are not the *primary* or most common presentation of the disease. **High-Yield Clinical Pearls for NEET-PG:** * **Histopathology:** Look for the "saw-tooth" appearance of rete pegs, basal cell degeneration (liquefaction necrosis), and a band-like lymphocytic infiltrate at the dermo-epidermal junction. * **Koebner Phenomenon:** LP shows a positive Koebner phenomenon (lesions appearing at sites of trauma). * **Associations:** Often associated with **Hepatitis C** infection. * **Civatte Bodies:** These are apoptotic keratinocytes found in the lower epidermis/upper dermis, also known as colloid or cytoid bodies.

Q: Which of the following is not a type of leukoplakia?

Bullous. **Explanation:** **Leukoplakia** is clinically defined as a "predominantly white patch or plaque of the oral mucosa that cannot be characterized clinically or pathologically as any other disease." It is a premalignant condition. **Why Bullous is the correct answer:** Leukoplakia is classified based on its clinical morphology into **Homogenous** and **Non-homogenous** types. **Bullous** is not a recognized clinical variant of leukoplakia. Bullous lesions (blisters) are characteristic of immunobullous disorders (like Pemphigus) or infections, but they do not form the clinical spectrum of leukoplakia, which is primarily a keratotic or dysplastic process. **Analysis of Incorrect Options:** * **Homogenous (Option D):** This is the most common type. It presents as a uniform, flat, thin, white plaque with a smooth, wrinkled, or corrugated surface. It carries a lower risk of malignancy. * **Non-Homogenous types:** These carry a higher risk of malignant transformation and include: * **Speckled (Option C):** Also known as Erythroleukoplakia. It consists of white flecks or nodules on an erythematous (red) base. * **Ulcerative (Option A):** Characterized by an ulcerated area within the white patch; this is often a red flag for invasive squamous cell carcinoma. * **Verrucous:** A subtype with a thick, wart-like, irregular surface. **Clinical Pearls for NEET-PG:** * **Most common site:** Buccal mucosa. * **Highest risk of malignancy:** Speckled (Erythroleukoplakia) and Proliferative Verrucous Leukoplakia (PVL). * **Biopsy:** Mandatory to rule out dysplasia or Squamous Cell Carcinoma (SCC). * **Hairy Leukoplakia:** Unlike oral leukoplakia, this is caused by **EBV** in HIV patients and is *not* premalignant.

Q: Facial edema, cheilitis granulomatosa, and a fissured tongue characterize which of the following syndromes?

Melkerson-Rosenthal syndrome. **Explanation:** **Melkersson-Rosenthal Syndrome (MRS)** is a rare neurocutaneous disorder characterized by a classic diagnostic triad. The correct answer is B because the question describes this specific triad: 1. **Recurrent facial edema:** Usually non-pitting and painless, most commonly involving the lips. 2. **Cheilitis granulomatosa:** Chronic swelling of the lip due to granulomatous inflammation (Miescher’s cheilitis is considered a monosymptomatic form of MRS). 3. **Fissured tongue (Lingua plicata):** Present in approximately 30–50% of cases. **Analysis of Incorrect Options:** * **A. Frey's Syndrome (Auriculotemporal Syndrome):** Characterized by localized sweating and flushing in the parotid area while eating (gustatory sweating), usually following parotid surgery or trauma. It does not involve tongue fissuring or granulomatous cheilitis. * **C. Treacher Collins Syndrome:** A genetic disorder of craniofacial development (mandibulofacial dysostosis) presenting with downward-slanting eyes, micrognathia, and malformed ears. It is a structural developmental defect, not an inflammatory/edematous condition. **NEET-PG High-Yield Pearls:** * **The Triad:** Only about 20–25% of patients present with the complete triad simultaneously. * **Facial Nerve Palsy:** Recurrent, lower motor neuron type facial palsy is the third component of the triad (often replacing or accompanying the edema). * **Histopathology:** Skin biopsy of the lip shows **non-caseating granulomas**, similar to sarcoidosis or Crohn’s disease. * **Mnemonic:** Remember **"M-R-S"** — **M**outh (Cheilitis), **R**elapsing paralysis (Facial palsy), **S**plit tongue (Fissured).

Q: Xanthoma disseminatum is associated with which of the following conditions?

Diabetes Insipidus. **Explanation:** **Xanthoma disseminatum (XD)** is a rare, benign, non-Langerhans cell histiocytosis (non-LCH). It is characterized by the triad of **cutaneous xanthomas**, **mucosal involvement**, and **diabetes insipidus**. 1. **Why Diabetes Insipidus is correct:** The underlying pathophysiology involves the proliferation of histiocytes in various tissues. In approximately **40% of cases**, these histiocytic infiltrates involve the pituitary stalk or the hypothalamus. This leads to a deficiency in Vasopressin (ADH), resulting in **central Diabetes Insipidus**. The cutaneous lesions typically appear as small, reddish-brown to yellow papules and nodules symmetrically distributed over the face and flexural areas (axilla, groin). 2. **Why the other options are incorrect:** * **A. Down’s Syndrome:** While associated with certain dermatological conditions like syringomas and alopecia areata, it has no known association with XD. * **C. Lymphoma:** XD is a benign histiocytic proliferation. While some other xanthomatous conditions (like Necrobiotic Xanthogranuloma) are associated with paraproteinemias or malignancies, XD is not typically linked to lymphoma. * **D. Carcinoma of Pancreas:** There is no established clinical link between XD and pancreatic malignancy. **High-Yield Clinical Pearls for NEET-PG:** * **Normolipemic State:** Unlike most other xanthomas, Xanthoma Disseminatum occurs in patients with **normal lipid profiles**. * **The Triad:** Cutaneous lesions + Mucosal lesions (upper airway/oral) + Diabetes Insipidus. * **Montgomery’s Syndrome:** Another name for Xanthoma Disseminatum. * **Histology:** Features "Touton giant cells" and foamy macrophages (histiocytes) that are **S100 negative** and **CD68 positive** (confirming non-LCH origin).

Question 1

Which sign is pathognomonic for neurofibromatosis?

Accepted Answer

Axillary freckling

Answer

Cafe-au-lait macules

Answer

Shagreen patch

Answer

None of the above

Question 2

What is the primary lesion in lichen planus?

Accepted Answer

Papule

Answer

Macule

Answer

Vesicle

Answer

Bullae

Question 3

Which of the following is not a type of leukoplakia?

Accepted Answer

Bullous

Answer

Ulcerative

Answer

Speckled

Answer

Homogenous

Question 4

Facial edema, cheilitis granulomatosa, and a fissured tongue characterize which of the following syndromes?

Accepted Answer

Melkerson-Rosenthal syndrome

Answer

Frey's syndrome

Answer

Treacher Collins syndrome

Answer

None of the above

Question 5

Xanthoma disseminatum is associated with which of the following conditions?

Accepted Answer

Diabetes Insipidus

Answer

Down's Syndrome

Answer

Lymphoma

Answer

Carcinoma of Pancreas

Basic Dermatology — MCQs

Basic Dermatology — MCQs

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