Basic Dermatology — MCQs

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).

Q: Chronic urticaria is considered which type of hypersensitivity reaction?

Type 1 hypersensitivity reaction. **Explanation:** **Correct Option: A (Type 1 Hypersensitivity Reaction)** Urticaria (hives) is the classic clinical manifestation of a **Type 1 (Immediate) Hypersensitivity reaction**. The underlying mechanism involves the cross-linking of **IgE antibodies** bound to the surface of **mast cells** and basophils by a specific antigen. This triggers degranulation, leading to the release of potent inflammatory mediators, primarily **histamine**. Histamine increases vascular permeability and causes vasodilation, resulting in the characteristic "wheal and flare" appearance (dermal edema and erythema). While chronic urticaria (lasting >6 weeks) often has an autoimmune component (IgG against IgE or its receptor), it is functionally classified under Type 1 mechanisms due to the end-pathway of mast cell degranulation. **Why other options are incorrect:** * **Type 2 (Cytotoxic):** Involves IgG/IgM antibodies directed against cell surface antigens leading to cell lysis (e.g., Pemphigus vulgaris, Bullous pemphigoid). * **Type 3 (Immune-Complex):** Caused by the deposition of antigen-antibody complexes in tissues, leading to complement activation (e.g., SLE, Vasculitis). * **Type 4 (Delayed-type):** T-cell mediated reaction occurring 48–72 hours after exposure (e.g., Allergic Contact Dermatitis, Lepromin test). **High-Yield Clinical Pearls for NEET-PG:** * **Definition:** Chronic urticaria is defined by the presence of wheals for **>6 weeks**. * **Dermographism:** The most common form of physical urticaria (wheal formation upon stroking the skin). * **Angioedema:** When the swelling involves the deep dermis and subcutaneous tissue; it is often associated with urticaria. * **Treatment of Choice:** Second-generation **non-sedating H1 antihistamines** (e.g., Cetirizine, Loratadine). For refractory chronic cases, **Omalizumab** (anti-IgE antibody) is highly effective.

Q: "Herald patch" is a characteristic feature of which condition?

Pityriasis rosea. **Explanation:** **Pityriasis Rosea (PR)** is a common, self-limiting inflammatory skin disorder. The **Herald Patch** is its hallmark clinical feature, appearing in 50–90% of cases. It is a single, primary, oval erythematous lesion (2–10 cm) with a peripheral "collarette" of scaling, typically located on the trunk. Days to weeks later, a generalized eruption of smaller maculopapular lesions follows, aligned along skin tension lines (Langer’s lines), creating the classic **"Christmas Tree" distribution.** **Why other options are incorrect:** * **Pityriasis Rubra Pilaris (PRP):** Characterized by follicular papules on an erythematous base, "islands of sparing" (normal skin within affected areas), and orange-red keratoderma of palms and soles. * **Psoriasis:** Presents as well-demarcated, silvery-white micaceous scales on an erythematous base. Key signs include **Auspitz sign** and **Koebner phenomenon**, but no herald patch. * **Lichen Planus:** Defined by the "6 Ps" (Planar, Purple, Polygonal, Pruritic, Papules, and Plaques). It features **Wickham striae** (white reticular patterns) rather than a herald patch. **High-Yield Clinical Pearls for NEET-PG:** * **Etiology:** Associated with **HHV-6 and HHV-7** reactivation. * **Collarette Scale:** The scale is attached peripherally with a free central edge. * **Differential Diagnosis:** Secondary syphilis (always rule out if palms/soles are involved) and Tinea corporis (which has a central clearing but lacks the subsequent generalized eruption). * **Treatment:** Usually expectant (reassurance); antihistamines for pruritus.

Q: Which of the following is a feature of Neurofibromatosis type 1?

All of the above. **Explanation:** Neurofibromatosis Type 1 (NF1), also known as **von Recklinghausen disease**, is an autosomal dominant neurocutaneous syndrome caused by a mutation in the *NF1* gene on **chromosome 17**. The diagnosis is primarily clinical, based on the **NIH Diagnostic Criteria**, which requires at least two of the seven cardinal features. **Why "All of the above" is correct:** * **Axillary freckling (Crowe sign):** This is a highly specific diagnostic feature of NF1. It refers to small, 1–3 mm hyperpigmented macules in the axillary or inguinal folds. * **Optic glioma:** This is the most common CNS tumor associated with NF1, typically occurring in early childhood. It is one of the major NIH criteria. * **Positive family history:** Since NF1 is an autosomal dominant condition with high penetrance, a first-degree relative (parent, sibling, or child) with NF1 is a diagnostic criterion. **Clinical Pearls for NEET-PG:** To master NF1 questions, remember the **NIH Diagnostic Criteria (Rule of 2s)**: 1. **6 or more Café-au-lait macules** (>5mm in prepubertal, >15mm in postpubertal). 2. **2 or more Neurofibromas** (any type) or one plexiform neurofibroma. 3. **Axillary or inguinal freckling**. 4. **Optic glioma**. 5. **2 or more Lisch nodules** (iris hamartomas seen on slit-lamp exam). 6. **Distinctive bony lesions** (e.g., sphenoid dysplasia or thinning of long bone cortex). 7. **First-degree relative** with NF1. **High-Yield Note:** NF1 is associated with **Lisch nodules**, whereas NF2 is associated with **posterior subcapsular cataracts** and bilateral acoustic neuromas.

Q: A patient with a history of smoking, essential hypertension, hypercholesterolemia, and hyperuricemia presents for follow-up. Oral examination findings from three visits are available. What is the most likely diagnosis of the tongue involvement?

Geographic tongue. ***Geographic tongue*** - Characterized by **migratory erythematous patches** with **white or yellow borders** that change location and appearance across multiple visits, explaining the varying oral examination findings. - Also known as **benign migratory glossitis**, it presents as **depapillated areas** on the tongue dorsum that create a map-like appearance and is often asymptomatic. *Oral candidiasis* - Presents as **white plaques** that can be **wiped off** easily, leaving an erythematous base underneath. - Typically associated with **immunocompromised states**, antibiotic use, or diabetes, and would show consistent findings rather than changing patterns across visits. *Lichen planus* - Characterized by **white lacy streaks** (Wickham's striae) or **reticular patterns** that remain relatively stable over time. - Often involves **bilateral buccal mucosa** and may cause **erosive lesions** with burning sensation, unlike the migrating nature seen in this case. *Oral hairy leukoplakia* - Presents as **white, corrugated patches** on the **lateral borders** of the tongue that cannot be wiped off. - Strongly associated with **HIV infection** and **Epstein-Barr virus**, showing consistent appearance rather than the changing pattern described across multiple visits.

Basic Dermatology Indian Medical PG Practice Questions and MCQs

Question 1: Which sign is pathognomonic for neurofibromatosis?

A. Cafe-au-lait macules
B. Axillary freckling (Correct Answer)
C. Shagreen patch
D. None of the above

Explanation: **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).

Question 2: What is the primary lesion in lichen planus?

A. Macule
B. Papule (Correct Answer)
C. Vesicle
D. Bullae

Explanation: **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; bullae >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.

Question 3: Which of the following is not a type of leukoplakia?

A. Ulcerative
B. Bullous (Correct Answer)
C. Speckled
D. Homogenous

Explanation: **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.

Question 4: Facial edema, cheilitis granulomatosa, and a fissured tongue characterize which of the following syndromes?

A. Frey's syndrome
B. Melkerson-Rosenthal syndrome (Correct Answer)
C. Treacher Collins syndrome
D. None of the above

Explanation: **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).

Question 5: Xanthoma disseminatum is associated with which of the following conditions?

A. Down's Syndrome
B. Diabetes Insipidus (Correct Answer)
C. Lymphoma
D. Carcinoma of Pancreas

Explanation: **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 6: Chronic urticaria is considered which type of hypersensitivity reaction?

A. Type 1 hypersensitivity reaction (Correct Answer)
B. Type 2 hypersensitivity reaction
C. Type 3 hypersensitivity reaction
D. Type 4 hypersensitivity reaction

Explanation: **Explanation:** **Correct Option: A (Type 1 Hypersensitivity Reaction)** Urticaria (hives) is the classic clinical manifestation of a **Type 1 (Immediate) Hypersensitivity reaction**. The underlying mechanism involves the cross-linking of **IgE antibodies** bound to the surface of **mast cells** and basophils by a specific antigen. This triggers degranulation, leading to the release of potent inflammatory mediators, primarily **histamine**. Histamine increases vascular permeability and causes vasodilation, resulting in the characteristic "wheal and flare" appearance (dermal edema and erythema). While chronic urticaria (lasting >6 weeks) often has an autoimmune component (IgG against IgE or its receptor), it is functionally classified under Type 1 mechanisms due to the end-pathway of mast cell degranulation. **Why other options are incorrect:** * **Type 2 (Cytotoxic):** Involves IgG/IgM antibodies directed against cell surface antigens leading to cell lysis (e.g., Pemphigus vulgaris, Bullous pemphigoid). * **Type 3 (Immune-Complex):** Caused by the deposition of antigen-antibody complexes in tissues, leading to complement activation (e.g., SLE, Vasculitis). * **Type 4 (Delayed-type):** T-cell mediated reaction occurring 48–72 hours after exposure (e.g., Allergic Contact Dermatitis, Lepromin test). **High-Yield Clinical Pearls for NEET-PG:** * **Definition:** Chronic urticaria is defined by the presence of wheals for **>6 weeks**. * **Dermographism:** The most common form of physical urticaria (wheal formation upon stroking the skin). * **Angioedema:** When the swelling involves the deep dermis and subcutaneous tissue; it is often associated with urticaria. * **Treatment of Choice:** Second-generation **non-sedating H1 antihistamines** (e.g., Cetirizine, Loratadine). For refractory chronic cases, **Omalizumab** (anti-IgE antibody) is highly effective.

Question 7: "Herald patch" is a characteristic feature of which condition?

A. Pityriasis rubra pilaris
B. Psoriasis
C. Lichen planus
D. Pityriasis rosea (Correct Answer)

Explanation: **Explanation:** **Pityriasis Rosea (PR)** is a common, self-limiting inflammatory skin disorder. The **Herald Patch** is its hallmark clinical feature, appearing in 50–90% of cases. It is a single, primary, oval erythematous lesion (2–10 cm) with a peripheral "collarette" of scaling, typically located on the trunk. Days to weeks later, a generalized eruption of smaller maculopapular lesions follows, aligned along skin tension lines (Langer’s lines), creating the classic **"Christmas Tree" distribution.** **Why other options are incorrect:** * **Pityriasis Rubra Pilaris (PRP):** Characterized by follicular papules on an erythematous base, "islands of sparing" (normal skin within affected areas), and orange-red keratoderma of palms and soles. * **Psoriasis:** Presents as well-demarcated, silvery-white micaceous scales on an erythematous base. Key signs include **Auspitz sign** and **Koebner phenomenon**, but no herald patch. * **Lichen Planus:** Defined by the "6 Ps" (Planar, Purple, Polygonal, Pruritic, Papules, and Plaques). It features **Wickham striae** (white reticular patterns) rather than a herald patch. **High-Yield Clinical Pearls for NEET-PG:** * **Etiology:** Associated with **HHV-6 and HHV-7** reactivation. * **Collarette Scale:** The scale is attached peripherally with a free central edge. * **Differential Diagnosis:** Secondary syphilis (always rule out if palms/soles are involved) and Tinea corporis (which has a central clearing but lacks the subsequent generalized eruption). * **Treatment:** Usually expectant (reassurance); antihistamines for pruritus.

Question 8: Which of the following is a feature of Neurofibromatosis type 1?

A. Axillary freckling
B. Optic glioma
C. Positive family history
D. All of the above (Correct Answer)

Explanation: **Explanation:** Neurofibromatosis Type 1 (NF1), also known as **von Recklinghausen disease**, is an autosomal dominant neurocutaneous syndrome caused by a mutation in the *NF1* gene on **chromosome 17**. The diagnosis is primarily clinical, based on the **NIH Diagnostic Criteria**, which requires at least two of the seven cardinal features. **Why "All of the above" is correct:** * **Axillary freckling (Crowe sign):** This is a highly specific diagnostic feature of NF1. It refers to small, 1–3 mm hyperpigmented macules in the axillary or inguinal folds. * **Optic glioma:** This is the most common CNS tumor associated with NF1, typically occurring in early childhood. It is one of the major NIH criteria. * **Positive family history:** Since NF1 is an autosomal dominant condition with high penetrance, a first-degree relative (parent, sibling, or child) with NF1 is a diagnostic criterion. **Clinical Pearls for NEET-PG:** To master NF1 questions, remember the **NIH Diagnostic Criteria (Rule of 2s)**: 1. **6 or more Café-au-lait macules** (>5mm in prepubertal, >15mm in postpubertal). 2. **2 or more Neurofibromas** (any type) or one plexiform neurofibroma. 3. **Axillary or inguinal freckling**. 4. **Optic glioma**. 5. **2 or more Lisch nodules** (iris hamartomas seen on slit-lamp exam). 6. **Distinctive bony lesions** (e.g., sphenoid dysplasia or thinning of long bone cortex). 7. **First-degree relative** with NF1. **High-Yield Note:** NF1 is associated with **Lisch nodules**, whereas NF2 is associated with **posterior subcapsular cataracts** and bilateral acoustic neuromas.

Question 9: A patient with a history of smoking, essential hypertension, hypercholesterolemia, and hyperuricemia presents for follow-up. Oral examination findings from three visits are available. What is the most likely diagnosis of the tongue involvement?

A. Geographic tongue (Correct Answer)
B. Oral candidiasis
C. Lichen planus
D. Oral hairy leukoplakia

Explanation: ***Geographic tongue*** - Characterized by **migratory erythematous patches** with **white or yellow borders** that change location and appearance across multiple visits, explaining the varying oral examination findings. - Also known as **benign migratory glossitis**, it presents as **depapillated areas** on the tongue dorsum that create a map-like appearance and is often asymptomatic. *Oral candidiasis* - Presents as **white plaques** that can be **wiped off** easily, leaving an erythematous base underneath. - Typically associated with **immunocompromised states**, antibiotic use, or diabetes, and would show consistent findings rather than changing patterns across visits. *Lichen planus* - Characterized by **white lacy streaks** (Wickham's striae) or **reticular patterns** that remain relatively stable over time. - Often involves **bilateral buccal mucosa** and may cause **erosive lesions** with burning sensation, unlike the migrating nature seen in this case. *Oral hairy leukoplakia* - Presents as **white, corrugated patches** on the **lateral borders** of the tongue that cannot be wiped off. - Strongly associated with **HIV infection** and **Epstein-Barr virus**, showing consistent appearance rather than the changing pattern described across multiple visits.

Question 10: A 40-year-old diabetic patient presents with round lesions on the abdomen for 2 weeks. Histopathology shows a palisading granuloma. What is the diagnosis?

A. Granuloma annulare (Correct Answer)
B. Pemphigus erythematosus
C. Leprosy
D. Tinea

Explanation: **Explanation:** The clinical presentation and histopathology point towards **Granuloma Annulare (GA)**. **1. Why Granuloma Annulare is correct:** * **Clinical Presentation:** GA typically presents as asymptomatic, skin-colored to erythematous, annular (ring-shaped) plaques. While the localized form is most common on distal extremities, it can occur on the trunk. * **Association:** There is a well-documented (though sometimes debated) clinical association between **Diabetes Mellitus** and the generalized/disseminated form of GA. * **Histopathology:** This is the "gold standard" for diagnosis. GA is characterized by a **palisading granuloma** in the dermis, consisting of a central area of **necrobiosis** (altered collagen) surrounded by a "picket fence" of histiocytes, lymphocytes, and increased **mucin** deposition. **2. Why other options are incorrect:** * **Pemphigus erythematosus:** An autoimmune bullous disease (Senear-Usher syndrome) combining features of Pemphigus and SLE. Histology shows acantholysis and subepidermal clefting, not granulomas. * **Leprosy:** Tuberculoid leprosy (TT) shows granulomas, but they are typically **epithelioid granulomas** that follow neurovascular bundles (perineural distribution). It presents with anesthetic patches. * **Tinea:** A fungal infection presenting with annular lesions with active scaling borders. Histology shows fungal hyphae in the stratum corneum (PAS positive), not dermal granulomas. **NEET-PG High-Yield Pearls:** * **Palisading Granulomas Mnemonic (M-N-G):** **M**yxoid (Granuloma Annulare - has Mucin), **N**ecrobiotic (Necrobiosis Lipoidica - has "layered" or "tier-like" granulomas), **G**outy tophi. * **GA vs. NLD:** Both are associated with Diabetes. However, **Necrobiosis Lipoidica (NLD)** typically occurs on the shins (pretibial) and shows "naked" or "tiered" granulomas with plasma cells and prominent collagen sclerosis, unlike the mucin-rich palisading of GA. * **Treatment:** Often self-limiting; topical steroids or intralesional triamcinolone are first-line.

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