Pediatric Dermatology — MCQs

Q: A child presents with a history of hypopigmented macules on the back, infantile spasms, and delayed milestones. What is the most likely diagnosis?

Tuberous sclerosis. ### Explanation **Correct Answer: C. Tuberous Sclerosis (TSC)** The clinical triad of **hypopigmented macules (Ash-leaf spots)**, **infantile spasms** (West Syndrome), and **delayed milestones** is classic for Tuberous Sclerosis Complex. * **Pathophysiology:** TSC is an autosomal dominant neurocutaneous syndrome caused by mutations in the *TSC1* (Hamartin) or *TSC2* (Tuberin) genes, leading to the overactivation of the mTOR pathway and the formation of hamartomas in multiple organs. * **Dermatological markers:** Ash-leaf spots are often the earliest sign. Other features include Adenoma sebaceum (angiofibromas), Shagreen patches (connective tissue nevi), and periungual fibromas (Koenen tumors). * **Neurological markers:** Cortical tubers and subependymal nodules lead to seizures (infantile spasms) and intellectual disability. **Why Incorrect Options are Wrong:** * **A. Neurofibromatosis:** Characterized by *hyperpigmented* Café-au-lait macules, Lisch nodules, and neurofibromas, rather than hypopigmentation and infantile spasms. * **B. Sturge-Weber Syndrome:** Presents with a Port-wine stain (Nevus Flammeus) in the V1/V2 distribution of the trigeminal nerve, glaucoma, and leptomeningeal angiomas. * **C. Nevus Anemicus:** A localized vascular anomaly presenting as a pale patch due to catecholamine sensitivity. It does not cause systemic neurological symptoms or developmental delay. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest sign:** Ash-leaf spots (best seen under **Wood’s lamp**). * **Most common heart lesion:** Rhabdomyoma (often regresses spontaneously). * **Most common kidney lesion:** Angiomyolipoma. * **Drug of choice for Infantile Spasms in TSC:** Vigabatrin. * **Pathognomonic sign:** Koenen tumors (Periungual fibromas).

Q: A 14-year-old boy presents with seizures and skin macules. What is the probable diagnosis?

Tuberous sclerosis. ### Explanation **Correct Answer: C. Tuberous Sclerosis (TSC)** The combination of **seizures** and **skin macules** (specifically hypopigmented "Ash-leaf" spots) is a classic presentation of Tuberous Sclerosis Complex, a neurocutaneous syndrome inherited in an autosomal dominant fashion (TSC1/TSC2 gene mutations). * **Why it is correct:** In pediatric dermatology, the earliest sign of TSC is often the **Ash-leaf macule** (hypopigmented macules visible under Wood’s lamp). The involvement of the Central Nervous System leads to cortical tubers and subependymal nodules, which manifest clinically as **seizures** and intellectual disability (the "Vogt’s Triad": Seizures, Mental Retardation, and Adenoma Sebaceum). **Analysis of Incorrect Options:** * **A. Sturge-Weber Syndrome:** Characterized by a **Port-wine stain** (Nevus Flammeus) usually in the V1/V2 distribution of the trigeminal nerve. While it causes seizures, the skin lesion is a vascular malformation, not a macule. * **B. Turcot Syndrome:** A variant of Familial Adenomatous Polyposis (FAP) associated with CNS tumors (medulloblastoma/glioma) and colonic polyps. It does not typically present with characteristic skin macules. * **C. Von Hippel-Lindau (VHL) Disease:** Characterized by hemangioblastomas (retina/cerebellum) and renal cell carcinoma. It lacks the specific cutaneous macules associated with seizures in childhood. **High-Yield Clinical Pearls for NEET-PG:** 1. **Skin Findings in TSC:** Ash-leaf spots (earliest), Adenoma Sebaceum (angiofibromas), Shagreen patches (connective tissue nevi), and Periungual fibromas (Koenen tumors). 2. **Diagnostic Triad (Vogt’s):** Epilepsy, Low IQ, and Adenoma Sebaceum (only present in ~30% of cases). 3. **Other Associations:** Cardiac rhabdomyomas (often regress), Renal Angiomyolipomas (AML), and Lymphangioleiomyomatosis (LAM) in the lungs. 4. **Wood’s Lamp:** Essential for identifying Ash-leaf spots in fair-skinned children.

Q: In infancy, atopic dermatitis typically spares which of the following areas?

Diaper area. **Explanation:** Atopic Dermatitis (AD) is a chronic, pruritic inflammatory skin disease that follows a characteristic age-dependent distribution. In **infancy** (birth to 2 years), the correct answer is the **Diaper area (Option D)**. **Why the Diaper Area is Spared:** The diaper area is typically spared in infantile AD because the high humidity and moisture trapped by the diaper prevent skin dehydration (transepidermal water loss). Since xerosis (dryness) is a primary trigger for AD, the "occlusive" effect of the diaper protects this specific region. If a rash is present in the diaper area, clinicians should consider Seborrheic Dermatitis or Irritant Diaper Dermatitis instead. **Analysis of Incorrect Options:** * **A. Extensor surfaces:** These are the classic sites for AD in infants. As babies begin to crawl, the friction on the knees and elbows triggers the "itch-scratch cycle." * **B. Forehead & C. Scalp:** The face (especially the cheeks and forehead) and the scalp are often the first sites involved in infancy. The lesions are typically acute, presenting as erythematous, edematous, and sometimes weeping plaques. **High-Yield Clinical Pearls for NEET-PG:** * **Evolution of Sites:** * **Infancy:** Face, scalp, and extensors (spares diaper area). * **Childhood/Adulthood:** Flexural surfaces (antecubital and popliteal fossae), neck, and wrists. * **Hertoghe’s Sign:** Thinning of the lateral third of the eyebrows (due to chronic rubbing). * **Dennie-Morgan Fold:** An extra fold of skin under the lower eyelid. * **Filaggrin (FLG) Mutation:** The most common genetic defect associated with skin barrier dysfunction in AD.

Q: Ectodermal dysplasia is characterized by which of the following manifestations?

All of the above. **Explanation:** **Ectodermal Dysplasia (ED)** refers to a large, heterogeneous group of genetic disorders characterized by the abnormal development of two or more structures derived from the **embryonic ectoderm**. The most common form is **Hypohidrotic Ectodermal Dysplasia (Christ-Siemens-Touraine syndrome)**, typically inherited in an X-linked recessive pattern. The "Classic Triad" of Ectodermal Dysplasia includes: 1. **Hypohidrosis (Option A):** Reduced or absent sweat glands (aplasia/hypoplasia), leading to heat intolerance and life-threatening pyrexia in infancy. 2. **Hypotrichosis (Option B):** Sparse, fine, light-colored scalp and body hair. Eyebrows and eyelashes are often absent or thinned. 3. **Hypodontia/Anodontia (Option C):** Missing teeth or malformed teeth (classically described as **peg-shaped** or conical incisors). Since all three clinical features are hallmark manifestations of the condition, **Option D (All of the above)** is the correct answer. **Clinical Pearls for NEET-PG:** * **Facial Profile:** Patients often exhibit "leonine facies" with frontal bossing, a depressed nasal bridge (saddle nose), and thick, everted lips. * **Skin:** The skin is typically thin, dry (xerosis), and hypopigmented. * **Genetics:** Most cases are due to mutations in the **EDA gene** (encoding Ectodysplasin-A). * **Differential Diagnosis:** Must be distinguished from *Incontinentia Pigmenti*, which also features dental anomalies but presents with distinct linear skin blistering and hyperpigmentation.

Q: A young boy presents with dark patches with itching. On rubbing, a wheal appears. What is the most likely diagnosis?

Urticaria pigmentosa. **Explanation:** The clinical presentation described is a classic manifestation of **Urticaria pigmentosa**, the most common form of cutaneous mastocytosis in children. **1. Why Urticaria Pigmentosa is correct:** The hallmark of this condition is the accumulation of mast cells in the dermis, presenting as reddish-brown macules or papules. The key diagnostic feature mentioned is the appearance of a wheal upon rubbing the lesion, known as the **Darier sign**. This occurs because physical stimulation causes mast cell degranulation, releasing histamine and other inflammatory mediators, leading to localized edema (wheal) and erythema (flare). **2. Why other options are incorrect:** * **Addison’s Disease:** Presents with generalized hyperpigmentation (especially in palmar creases and oral mucosa) due to ACTH excess, but it does not feature whealing or the Darier sign. * **Chronic Idiopathic Urticaria:** Characterized by transient wheals that resolve within 24 hours without leaving permanent dark patches. * **Erythema Multiforme:** Presents with characteristic "target" or "iris" lesions (dusky center, pale ring, erythematous border), usually triggered by infections like HSV. It does not present with persistent dark patches that wheal on rubbing. **High-Yield Clinical Pearls for NEET-PG:** * **Darier Sign:** Pathognomonic for mastocytosis (Urticaria pigmentosa). * **Mast Cell Triggers:** Patients should avoid triggers like NSAIDs, morphine, alcohol, and hot baths, which can cause systemic mast cell degranulation. * **Histology:** Shows an increased number of mast cells in the dermis, best visualized with special stains like **Toluidine blue** (shows metachromatic granules) or **Giemsa stain**. * **Prognosis:** Pediatric-onset urticaria pigmentosa often improves or resolves spontaneously by puberty.

Q: Which is not a feature of Netheon Syndrome?

Autosomal dominant. **Explanation:** **Netherton Syndrome** is a rare, severe multisystem disorder characterized by a classic clinical triad: **Ichthyosis linearis circumflexa**, **Hair shaft abnormalities**, and **Atopic features** [1], [2]. 1. **Why "Autosomal dominant" is the correct answer:** Netherton Syndrome is an **Autosomal Recessive** disorder [1]. It is caused by a mutation in the **SPINK5 gene** [2] on chromosome 5q32, which encodes the protein **LEKTI** (a serine protease inhibitor). The absence of LEKTI leads to uncontrolled protease activity in the epidermis, resulting in premature desquamation and a defective skin barrier. 2. **Why the other options are incorrect (Features of the syndrome):** * **Ichthyosis:** Specifically, patients develop **Ichthyosis linearis circumflexa**, characterized by migratory, erythematous, polycyclic plaques with a unique "double-edged" scale [2]. * **Very short hair:** This refers to **Trichorrhexis invaginata** (Bamboo hair), where the distal hair shaft intussuscepts into the proximal portion [1], [2]. This makes the hair extremely brittle, fragile, and short. * **Erythroderma:** Most affected infants present at birth with generalized **congenital ichthyosiform erythroderma**, which can lead to life-threatening complications like hypernatremic dehydration and sepsis. **NEET-PG High-Yield Pearls:** * **The Triad:** Ichthyosis + Trichorrhexis Invaginata + Atopy (elevated IgE/asthma) [1]. * **Pathognomonic Hair Sign:** Trichorrhexis invaginata (Bamboo hair) is considered pathognomonic for Netherton Syndrome [2]. * **Diagnosis:** Confirmed by skin biopsy (showing lack of LEKTI expression) or genetic testing for *SPINK5* [2]. * **Differential Diagnosis:** Often confused with Atopic Dermatitis or Omenn Syndrome in infancy due to the erythroderma and high IgE levels.

Q: A 2-month-old girl presents with a verrucous plaque on her trunk. What is your most probable diagnosis?

Incontinentia pigmentosa. ### Explanation **Incontinentia Pigmentosa (IP)**, also known as Bloch-Sulzberger syndrome, is an X-linked dominant neurocutaneous disorder that primarily affects females (lethal in males). The diagnosis is based on its classic **four-stage progression** of skin lesions: 1. **Stage 1 (Vesicular):** Linear blisters appearing at birth or shortly after. 2. **Stage 2 (Verrucous):** Hyperkeratotic, wart-like plaques, typically appearing between **2 to 8 weeks of age**. 3. **Stage 3 (Hyperpigmented):** "Swirl-like" or "Marble cake" pigmentation along Blaschko’s lines. 4. **Stage 4 (Atrophic):** Hypopigmented, hairless cicatricial streaks. The presentation of a **verrucous plaque in a 2-month-old** fits perfectly with the second stage of IP. **Analysis of Incorrect Options:** * **B. Darier’s disease:** (Likely intended by "Dearth's") This is an autosomal dominant disorder presenting with greasy, malodorous papules in seborrheic areas, usually appearing in adolescence, not infancy. * **C. Congenital nevus:** These are typically pigmented (brown/black) macules or plaques present at birth. While they can be thick, they do not follow the classic verrucous evolutionary stages seen in IP. * **D. Ichthyosis:** This refers to generalized scaling of the skin (e.g., Ichthyosis vulgaris or Lamellar ichthyosis). It does not present as localized verrucous plaques in a linear distribution. **NEET-PG High-Yield Pearls:** * **Genetics:** Mutation in the **IKBKG (NEMO) gene**. * **Distribution:** Lesions follow **Blaschko’s lines**. * **Associated Findings:** Peg-shaped teeth (hypodontia), cicatricial alopecia, and retinal vascular abnormalities. * **Histology (Stage 1):** Characterized by **eosinophilic spongiosis**.

Q: A 7-year-old child presents with a hypo-pigmented anesthetic patch on the face. What is the most probable diagnosis?

Intermediate leprosy. ### Explanation The diagnosis of **Indeterminate Leprosy** is based on the classic clinical triad of leprosy: a hypopigmented patch, loss of sensation, and (potentially) nerve involvement. **1. Why Indeterminate Leprosy is Correct:** In the context of pediatric dermatology and the NEET-PG exam, a **hypopigmented patch with anesthesia** (loss of sensation) is pathognomonic for leprosy. Indeterminate leprosy is the earliest clinical stage, often seen in children. It typically presents as a single, ill-defined, hypopigmented macule. While sensation may be only slightly diminished in early stages, the presence of anesthesia definitively points toward a mycobacterial infection affecting the dermal nerves. **2. Why Other Options are Incorrect:** * **Pityriasis alba:** Common in children; presents as multiple, ill-defined, scaly hypopigmented patches on the face. Crucially, **sensation is intact**, and it is often associated with atopy. * **Nevus anemicus:** A congenital vascular anomaly where the area appears pale due to localized hypersensitivity to catecholamines (vasoconstriction). Sensation is normal, and the patch **disappears on diascopy** (pressure with a glass slide) or rubbing. * **Nevus achromicus (Nevus Depigmentosus):** A stable, congenital hypopigmented birthmark. It has **normal sensation** and does not change in size or pigment over time. **Clinical Pearls for NEET-PG:** * **Earliest sign of Leprosy:** Usually a solitary hypopigmented macule (Indeterminate). * **First sensation lost:** Temperature (Cold/Hot), followed by Touch, Pain, and Deep Pressure. * **Face involvement:** In children, the face is a common site for leprosy due to increased exposure to the environment/vectors. * **Histopathology:** Indeterminate leprosy shows non-specific lymphocytic infiltration around dermal appendages and nerves; Acid-Fast Bacilli (AFB) are rarely found.

Q: Deficiency of which interleukin is associated with Ditra syndrome?

IL36. **Explanation:** **DITRA Syndrome** (Deficiency of IL-36 Receptor Antagonist) is a rare, life-threatening autoinflammatory disease characterized by recurrent episodes of generalized pustular psoriasis (GPP), high fever, and systemic inflammation. 1. **Why IL-36 is correct:** The syndrome is caused by a loss-of-function mutation in the **IL36RN gene**, which encodes the **IL-36 receptor antagonist (IL-36Ra)**. Normally, IL-36Ra acts as a "brake" by binding to the IL-36 receptor and blocking pro-inflammatory signaling. In DITRA, the absence of this antagonist leads to uncontrolled, overactive IL-36 signaling, resulting in massive recruitment of neutrophils and the formation of sterile pustules across the body. 2. **Why other options are incorrect:** * **IL-26:** A member of the IL-10 family involved in mucosal immunity and antimicrobial responses; it is not linked to DITRA. * **IL-46:** This is not a standard interleukin designation (Interleukins currently range from IL-1 to IL-40). * **IL-10:** An anti-inflammatory cytokine. While its deficiency can lead to early-onset inflammatory bowel disease (IBD), it is not the cause of DITRA. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Sudden onset of widespread sterile pustules on an erythematous base (von Zumbusch pattern), triggered by infections, stress, or pregnancy. * **Genetics:** Autosomal recessive inheritance. * **Treatment:** Targeted therapy with **Spesolimab** (an IL-36 receptor monoclonal antibody) is now the specific treatment of choice for GPP flares. * **Differential:** **DIRA** (Deficiency of IL-1 Receptor Antagonist) presents similarly but involves bone lesions (osteomyelitis) and is caused by mutations in the *IL1RN* gene.

Pediatric Dermatology Indian Medical PG Practice Questions and MCQs

Question 1: A child presents with a history of hypopigmented macules on the back, infantile spasms, and delayed milestones. What is the most likely diagnosis?

A. Neurofibromatosis
B. Sturge-Weber syndrome
C. Tuberous sclerosis (Correct Answer)
D. Nevus anemicus

Explanation: ### Explanation **Correct Answer: C. Tuberous Sclerosis (TSC)** The clinical triad of **hypopigmented macules (Ash-leaf spots)**, **infantile spasms** (West Syndrome), and **delayed milestones** is classic for Tuberous Sclerosis Complex. * **Pathophysiology:** TSC is an autosomal dominant neurocutaneous syndrome caused by mutations in the *TSC1* (Hamartin) or *TSC2* (Tuberin) genes, leading to the overactivation of the mTOR pathway and the formation of hamartomas in multiple organs. * **Dermatological markers:** Ash-leaf spots are often the earliest sign. Other features include Adenoma sebaceum (angiofibromas), Shagreen patches (connective tissue nevi), and periungual fibromas (Koenen tumors). * **Neurological markers:** Cortical tubers and subependymal nodules lead to seizures (infantile spasms) and intellectual disability. **Why Incorrect Options are Wrong:** * **A. Neurofibromatosis:** Characterized by *hyperpigmented* Café-au-lait macules, Lisch nodules, and neurofibromas, rather than hypopigmentation and infantile spasms. * **B. Sturge-Weber Syndrome:** Presents with a Port-wine stain (Nevus Flammeus) in the V1/V2 distribution of the trigeminal nerve, glaucoma, and leptomeningeal angiomas. * **C. Nevus Anemicus:** A localized vascular anomaly presenting as a pale patch due to catecholamine sensitivity. It does not cause systemic neurological symptoms or developmental delay. **High-Yield Clinical Pearls for NEET-PG:** * **Earliest sign:** Ash-leaf spots (best seen under **Wood’s lamp**). * **Most common heart lesion:** Rhabdomyoma (often regresses spontaneously). * **Most common kidney lesion:** Angiomyolipoma. * **Drug of choice for Infantile Spasms in TSC:** Vigabatrin. * **Pathognomonic sign:** Koenen tumors (Periungual fibromas).

Question 2: A 14-year-old boy presents with seizures and skin macules. What is the probable diagnosis?

A. Sturge-Weber syndrome
B. Turcot syndrome
C. Tuberous sclerosis (Correct Answer)
D. Von Hippel-Lindau disease

Explanation: ### Explanation **Correct Answer: C. Tuberous Sclerosis (TSC)** The combination of **seizures** and **skin macules** (specifically hypopigmented "Ash-leaf" spots) is a classic presentation of Tuberous Sclerosis Complex, a neurocutaneous syndrome inherited in an autosomal dominant fashion (TSC1/TSC2 gene mutations). * **Why it is correct:** In pediatric dermatology, the earliest sign of TSC is often the **Ash-leaf macule** (hypopigmented macules visible under Wood’s lamp). The involvement of the Central Nervous System leads to cortical tubers and subependymal nodules, which manifest clinically as **seizures** and intellectual disability (the "Vogt’s Triad": Seizures, Mental Retardation, and Adenoma Sebaceum). **Analysis of Incorrect Options:** * **A. Sturge-Weber Syndrome:** Characterized by a **Port-wine stain** (Nevus Flammeus) usually in the V1/V2 distribution of the trigeminal nerve. While it causes seizures, the skin lesion is a vascular malformation, not a macule. * **B. Turcot Syndrome:** A variant of Familial Adenomatous Polyposis (FAP) associated with CNS tumors (medulloblastoma/glioma) and colonic polyps. It does not typically present with characteristic skin macules. * **C. Von Hippel-Lindau (VHL) Disease:** Characterized by hemangioblastomas (retina/cerebellum) and renal cell carcinoma. It lacks the specific cutaneous macules associated with seizures in childhood. **High-Yield Clinical Pearls for NEET-PG:** 1. **Skin Findings in TSC:** Ash-leaf spots (earliest), Adenoma Sebaceum (angiofibromas), Shagreen patches (connective tissue nevi), and Periungual fibromas (Koenen tumors). 2. **Diagnostic Triad (Vogt’s):** Epilepsy, Low IQ, and Adenoma Sebaceum (only present in ~30% of cases). 3. **Other Associations:** Cardiac rhabdomyomas (often regress), Renal Angiomyolipomas (AML), and Lymphangioleiomyomatosis (LAM) in the lungs. 4. **Wood’s Lamp:** Essential for identifying Ash-leaf spots in fair-skinned children.

Question 3: In infancy, atopic dermatitis typically spares which of the following areas?

A. Extensor surfaces
B. Forehead
C. Scalp
D. Diaper area (Correct Answer)

Explanation: **Explanation:** Atopic Dermatitis (AD) is a chronic, pruritic inflammatory skin disease that follows a characteristic age-dependent distribution. In **infancy** (birth to 2 years), the correct answer is the **Diaper area (Option D)**. **Why the Diaper Area is Spared:** The diaper area is typically spared in infantile AD because the high humidity and moisture trapped by the diaper prevent skin dehydration (transepidermal water loss). Since xerosis (dryness) is a primary trigger for AD, the "occlusive" effect of the diaper protects this specific region. If a rash is present in the diaper area, clinicians should consider Seborrheic Dermatitis or Irritant Diaper Dermatitis instead. **Analysis of Incorrect Options:** * **A. Extensor surfaces:** These are the classic sites for AD in infants. As babies begin to crawl, the friction on the knees and elbows triggers the "itch-scratch cycle." * **B. Forehead & C. Scalp:** The face (especially the cheeks and forehead) and the scalp are often the first sites involved in infancy. The lesions are typically acute, presenting as erythematous, edematous, and sometimes weeping plaques. **High-Yield Clinical Pearls for NEET-PG:** * **Evolution of Sites:** * **Infancy:** Face, scalp, and extensors (spares diaper area). * **Childhood/Adulthood:** Flexural surfaces (antecubital and popliteal fossae), neck, and wrists. * **Hertoghe’s Sign:** Thinning of the lateral third of the eyebrows (due to chronic rubbing). * **Dennie-Morgan Fold:** An extra fold of skin under the lower eyelid. * **Filaggrin (FLG) Mutation:** The most common genetic defect associated with skin barrier dysfunction in AD.

Question 4: Ectodermal dysplasia is characterized by which of the following manifestations?

A. Hypohidrosis
B. Hypotrichosis
C. Hypodontia
D. All of the above (Correct Answer)

Explanation: **Explanation:** **Ectodermal Dysplasia (ED)** refers to a large, heterogeneous group of genetic disorders characterized by the abnormal development of two or more structures derived from the **embryonic ectoderm**. The most common form is **Hypohidrotic Ectodermal Dysplasia (Christ-Siemens-Touraine syndrome)**, typically inherited in an X-linked recessive pattern. The "Classic Triad" of Ectodermal Dysplasia includes: 1. **Hypohidrosis (Option A):** Reduced or absent sweat glands (aplasia/hypoplasia), leading to heat intolerance and life-threatening pyrexia in infancy. 2. **Hypotrichosis (Option B):** Sparse, fine, light-colored scalp and body hair. Eyebrows and eyelashes are often absent or thinned. 3. **Hypodontia/Anodontia (Option C):** Missing teeth or malformed teeth (classically described as **peg-shaped** or conical incisors). Since all three clinical features are hallmark manifestations of the condition, **Option D (All of the above)** is the correct answer. **Clinical Pearls for NEET-PG:** * **Facial Profile:** Patients often exhibit "leonine facies" with frontal bossing, a depressed nasal bridge (saddle nose), and thick, everted lips. * **Skin:** The skin is typically thin, dry (xerosis), and hypopigmented. * **Genetics:** Most cases are due to mutations in the **EDA gene** (encoding Ectodysplasin-A). * **Differential Diagnosis:** Must be distinguished from *Incontinentia Pigmenti*, which also features dental anomalies but presents with distinct linear skin blistering and hyperpigmentation.

Question 5: A young boy presents with dark patches with itching. On rubbing, a wheal appears. What is the most likely diagnosis?

A. Addison's disease
B. Urticaria pigmentosa (Correct Answer)
C. Chronic idiopathic urticaria
D. Erythema multiforme

Explanation: **Explanation:** The clinical presentation described is a classic manifestation of **Urticaria pigmentosa**, the most common form of cutaneous mastocytosis in children. **1. Why Urticaria Pigmentosa is correct:** The hallmark of this condition is the accumulation of mast cells in the dermis, presenting as reddish-brown macules or papules. The key diagnostic feature mentioned is the appearance of a wheal upon rubbing the lesion, known as the **Darier sign**. This occurs because physical stimulation causes mast cell degranulation, releasing histamine and other inflammatory mediators, leading to localized edema (wheal) and erythema (flare). **2. Why other options are incorrect:** * **Addison’s Disease:** Presents with generalized hyperpigmentation (especially in palmar creases and oral mucosa) due to ACTH excess, but it does not feature whealing or the Darier sign. * **Chronic Idiopathic Urticaria:** Characterized by transient wheals that resolve within 24 hours without leaving permanent dark patches. * **Erythema Multiforme:** Presents with characteristic "target" or "iris" lesions (dusky center, pale ring, erythematous border), usually triggered by infections like HSV. It does not present with persistent dark patches that wheal on rubbing. **High-Yield Clinical Pearls for NEET-PG:** * **Darier Sign:** Pathognomonic for mastocytosis (Urticaria pigmentosa). * **Mast Cell Triggers:** Patients should avoid triggers like NSAIDs, morphine, alcohol, and hot baths, which can cause systemic mast cell degranulation. * **Histology:** Shows an increased number of mast cells in the dermis, best visualized with special stains like **Toluidine blue** (shows metachromatic granules) or **Giemsa stain**. * **Prognosis:** Pediatric-onset urticaria pigmentosa often improves or resolves spontaneously by puberty.

Question 6: Which is not a feature of Netheon Syndrome?

A. Autosomal dominant (Correct Answer)
B. Ichthyosis
C. Very short hair
D. Erythroderma

Explanation: **Explanation:** **Netherton Syndrome** is a rare, severe multisystem disorder characterized by a classic clinical triad: **Ichthyosis linearis circumflexa**, **Hair shaft abnormalities**, and **Atopic features** [1], [2]. 1. **Why "Autosomal dominant" is the correct answer:** Netherton Syndrome is an **Autosomal Recessive** disorder [1]. It is caused by a mutation in the **SPINK5 gene** [2] on chromosome 5q32, which encodes the protein **LEKTI** (a serine protease inhibitor). The absence of LEKTI leads to uncontrolled protease activity in the epidermis, resulting in premature desquamation and a defective skin barrier. 2. **Why the other options are incorrect (Features of the syndrome):** * **Ichthyosis:** Specifically, patients develop **Ichthyosis linearis circumflexa**, characterized by migratory, erythematous, polycyclic plaques with a unique "double-edged" scale [2]. * **Very short hair:** This refers to **Trichorrhexis invaginata** (Bamboo hair), where the distal hair shaft intussuscepts into the proximal portion [1], [2]. This makes the hair extremely brittle, fragile, and short. * **Erythroderma:** Most affected infants present at birth with generalized **congenital ichthyosiform erythroderma**, which can lead to life-threatening complications like hypernatremic dehydration and sepsis. **NEET-PG High-Yield Pearls:** * **The Triad:** Ichthyosis + Trichorrhexis Invaginata + Atopy (elevated IgE/asthma) [1]. * **Pathognomonic Hair Sign:** Trichorrhexis invaginata (Bamboo hair) is considered pathognomonic for Netherton Syndrome [2]. * **Diagnosis:** Confirmed by skin biopsy (showing lack of LEKTI expression) or genetic testing for *SPINK5* [2]. * **Differential Diagnosis:** Often confused with Atopic Dermatitis or Omenn Syndrome in infancy due to the erythroderma and high IgE levels.

Question 7: A 28-year-old G1P0 at 32 weeks gestation presents with itchy, erythematous papules on the extensor surfaces and trunk. There is no history of fever or use of new creams or lotions. What is the first-line treatment for this condition?

A. Antibiotic therapy
B. Antivirals and termination of pregnancy
C. Topical steroids and oral antihistamines (Correct Answer)
D. Oral steroids

Explanation: ### Explanation The clinical presentation of itchy, erythematous papules on the extensor surfaces and trunk during the third trimester is most consistent with **Atopic Eruption of Pregnancy (AEP)**. AEP is the most common dermatosis of pregnancy, encompassing conditions previously known as prurigo of pregnancy and pruritic folliculitis of pregnancy. **Why Option C is Correct:** The primary goal of managing AEP is symptomatic relief. **Topical corticosteroids** (low to medium potency) are the first-line treatment to reduce inflammation, while **oral antihistamines** (e.g., Cetirizine or Loratadine) are used to manage the intense pruritus. This condition is benign and does not pose a risk to the fetus, making conservative topical therapy the standard of care. **Why Other Options are Incorrect:** * **Option A:** Antibiotics are used for infections. AEP is an inflammatory/atopic condition, not an infectious one. * **Option B:** Antivirals and termination are irrelevant here. This might be confused with severe TORCH infections or life-threatening conditions, but AEP is a self-limiting skin condition. * **Option C:** Oral steroids are reserved for severe, refractory cases or conditions like Pemphigoid Gestationis. They are not first-line for AEP. **High-Yield Clinical Pearls for NEET-PG:** * **Atopic Eruption of Pregnancy (AEP):** Usually occurs in the **1st or 2nd trimester** (though can occur in the 3rd). It is the only pregnancy dermatosis that can occur early in pregnancy. * **PUPPP (Pruritic Urticarial Papules and Plaques of Pregnancy):** Characterized by lesions starting in **striae distensae** with **umbilical sparing**. Usually occurs in the 3rd trimester. * **Pemphigoid Gestationis:** An autoimmune bullous disorder; unlike PUPPP, it **involves the umbilicus** and requires direct immunofluorescence (DIF) for diagnosis. * **Intrahepatic Cholestasis of Pregnancy (ICP):** Presents with pruritus (especially palms and soles) **without a primary rash**. Associated with elevated bile acids and fetal risk.

Question 8: A 2-month-old girl presents with a verrucous plaque on her trunk. What is your most probable diagnosis?

A. Incontinentia pigmentosa (Correct Answer)
B. Dearth's disease
C. Congenital nevus
D. Ichthyosis

Explanation: ### Explanation **Incontinentia Pigmentosa (IP)**, also known as Bloch-Sulzberger syndrome, is an X-linked dominant neurocutaneous disorder that primarily affects females (lethal in males). The diagnosis is based on its classic **four-stage progression** of skin lesions: 1. **Stage 1 (Vesicular):** Linear blisters appearing at birth or shortly after. 2. **Stage 2 (Verrucous):** Hyperkeratotic, wart-like plaques, typically appearing between **2 to 8 weeks of age**. 3. **Stage 3 (Hyperpigmented):** "Swirl-like" or "Marble cake" pigmentation along Blaschko’s lines. 4. **Stage 4 (Atrophic):** Hypopigmented, hairless cicatricial streaks. The presentation of a **verrucous plaque in a 2-month-old** fits perfectly with the second stage of IP. **Analysis of Incorrect Options:** * **B. Darier’s disease:** (Likely intended by "Dearth's") This is an autosomal dominant disorder presenting with greasy, malodorous papules in seborrheic areas, usually appearing in adolescence, not infancy. * **C. Congenital nevus:** These are typically pigmented (brown/black) macules or plaques present at birth. While they can be thick, they do not follow the classic verrucous evolutionary stages seen in IP. * **D. Ichthyosis:** This refers to generalized scaling of the skin (e.g., Ichthyosis vulgaris or Lamellar ichthyosis). It does not present as localized verrucous plaques in a linear distribution. **NEET-PG High-Yield Pearls:** * **Genetics:** Mutation in the **IKBKG (NEMO) gene**. * **Distribution:** Lesions follow **Blaschko’s lines**. * **Associated Findings:** Peg-shaped teeth (hypodontia), cicatricial alopecia, and retinal vascular abnormalities. * **Histology (Stage 1):** Characterized by **eosinophilic spongiosis**.

Question 9: A 7-year-old child presents with a hypo-pigmented anesthetic patch on the face. What is the most probable diagnosis?

A. Intermediate leprosy (Correct Answer)
B. Pityriasis alba
C. Nevus anemicus
D. Nevus achromicus

Explanation: ### Explanation The diagnosis of **Indeterminate Leprosy** is based on the classic clinical triad of leprosy: a hypopigmented patch, loss of sensation, and (potentially) nerve involvement. **1. Why Indeterminate Leprosy is Correct:** In the context of pediatric dermatology and the NEET-PG exam, a **hypopigmented patch with anesthesia** (loss of sensation) is pathognomonic for leprosy. Indeterminate leprosy is the earliest clinical stage, often seen in children. It typically presents as a single, ill-defined, hypopigmented macule. While sensation may be only slightly diminished in early stages, the presence of anesthesia definitively points toward a mycobacterial infection affecting the dermal nerves. **2. Why Other Options are Incorrect:** * **Pityriasis alba:** Common in children; presents as multiple, ill-defined, scaly hypopigmented patches on the face. Crucially, **sensation is intact**, and it is often associated with atopy. * **Nevus anemicus:** A congenital vascular anomaly where the area appears pale due to localized hypersensitivity to catecholamines (vasoconstriction). Sensation is normal, and the patch **disappears on diascopy** (pressure with a glass slide) or rubbing. * **Nevus achromicus (Nevus Depigmentosus):** A stable, congenital hypopigmented birthmark. It has **normal sensation** and does not change in size or pigment over time. **Clinical Pearls for NEET-PG:** * **Earliest sign of Leprosy:** Usually a solitary hypopigmented macule (Indeterminate). * **First sensation lost:** Temperature (Cold/Hot), followed by Touch, Pain, and Deep Pressure. * **Face involvement:** In children, the face is a common site for leprosy due to increased exposure to the environment/vectors. * **Histopathology:** Indeterminate leprosy shows non-specific lymphocytic infiltration around dermal appendages and nerves; Acid-Fast Bacilli (AFB) are rarely found.

Question 10: Deficiency of which interleukin is associated with Ditra syndrome?

A. IL 26
B. IL 46
C. IL 10
D. IL36 (Correct Answer)

Explanation: **Explanation:** **DITRA Syndrome** (Deficiency of IL-36 Receptor Antagonist) is a rare, life-threatening autoinflammatory disease characterized by recurrent episodes of generalized pustular psoriasis (GPP), high fever, and systemic inflammation. 1. **Why IL-36 is correct:** The syndrome is caused by a loss-of-function mutation in the **IL36RN gene**, which encodes the **IL-36 receptor antagonist (IL-36Ra)**. Normally, IL-36Ra acts as a "brake" by binding to the IL-36 receptor and blocking pro-inflammatory signaling. In DITRA, the absence of this antagonist leads to uncontrolled, overactive IL-36 signaling, resulting in massive recruitment of neutrophils and the formation of sterile pustules across the body. 2. **Why other options are incorrect:** * **IL-26:** A member of the IL-10 family involved in mucosal immunity and antimicrobial responses; it is not linked to DITRA. * **IL-46:** This is not a standard interleukin designation (Interleukins currently range from IL-1 to IL-40). * **IL-10:** An anti-inflammatory cytokine. While its deficiency can lead to early-onset inflammatory bowel disease (IBD), it is not the cause of DITRA. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Sudden onset of widespread sterile pustules on an erythematous base (von Zumbusch pattern), triggered by infections, stress, or pregnancy. * **Genetics:** Autosomal recessive inheritance. * **Treatment:** Targeted therapy with **Spesolimab** (an IL-36 receptor monoclonal antibody) is now the specific treatment of choice for GPP flares. * **Differential:** **DIRA** (Deficiency of IL-1 Receptor Antagonist) presents similarly but involves bone lesions (osteomyelitis) and is caused by mutations in the *IL1RN* gene.

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