Pediatric 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: 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: Which of the following is NOT a feature of Netherton Syndrome?

Autosomal dominant inheritance. **Explanation:** Netherton Syndrome is a rare, severe multisystem disorder characterized by a classic triad of **ichthyosis linearis circumflexa**, **hair shaft abnormalities**, and **atopic features**. **1. Why Option A is the correct answer:** Netherton Syndrome is inherited in an **Autosomal Recessive** pattern, not autosomal dominant. It is caused by a mutation in the **SPINK5 gene** on chromosome 5q32, which encodes the serine protease inhibitor **LEKTI**. The deficiency of LEKTI leads to overactive epidermal proteases, resulting in premature desquamation and a severely compromised skin barrier. **2. Why the other options are incorrect:** * **B. Ichthyosis:** Patients typically present with **Ichthyosis Linearis Circumflexa (ILC)**, characterized by migratory, erythematous, polycyclic plaques with a unique "double-edged" scale. * **C. Very short hair:** This refers to **Trichorrhexis invaginata** (Bamboo hair), the pathognomonic hair defect. The hair is brittle and breaks easily, leading to short, sparse hair and eyebrows. * **D. Erythroderma:** Most neonates with Netherton Syndrome present at birth with generalized **congenital ichthyosiform erythroderma**, which can lead to life-threatening complications like dehydration and hypernatremia. **High-Yield Clinical Pearls for NEET-PG:** * **Pathognomonic Hair Sign:** "Bamboo hair" (intussusception of the distal hair shaft into the proximal portion). * **The Triad:** Ichthyosis + Trichorrhexis invaginata + Atopy (high IgE levels/asthma). * **Differential Diagnosis:** Often misdiagnosed as Atopic Dermatitis or Omenn Syndrome in infancy. * **Key Gene:** SPINK5 (LEKTI protein).

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: All of the following are seen in Neurofibromatosis, except?

Shagreen patch. **Explanation:** The correct answer is **C. Shagreen patch**. This is because Shagreen patches are a pathognomonic feature of **Tuberous Sclerosis (Epiloia)**, not Neurofibromatosis. A Shagreen patch is a connective tissue nevus, typically appearing as a leathery, "orange-peel" textured plaque on the lower back. **Analysis of Options:** * **A. Lisch nodules:** These are melanocytic hamartomas of the iris. They are the most common ocular finding in **Neurofibromatosis Type 1 (NF1)** and are present in over 90% of adult patients. * **B. Axillary freckling (Crowe’s sign):** This refers to multiple small hyperpigmented macules in the axillary or inguinal folds. It is a highly specific diagnostic criterion for NF1. * **D. Cafe-au-lait spots:** These are "coffee-with-milk" colored macules. For a diagnosis of NF1, there must be $\geq$ 6 spots measuring $>5$ mm (pre-pubertal) or $>15$ mm (post-pubertal). **High-Yield Clinical Pearls for NEET-PG:** * **NF1 (von Recklinghausen disease)** is caused by a mutation in the *NF1* gene on **Chromosome 17** (encodes Neurofibromin). * **Tuberous Sclerosis Complex (TSC)** is associated with the "Vogt’s Triad": Adenoma sebaceum (angiofibromas), Mental retardation, and Epilepsy. * **Differentiating Skin Signs:** * **NF1:** Cafe-au-lait spots, Lisch nodules, Neurofibromas, Optic gliomas. * **TSC:** Ash-leaf spots (earliest sign), Shagreen patch, Adenoma sebaceum, Periungual fibromas (Koenen tumors).

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

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

Accepted Answer

Tuberous sclerosis

Answer

Sturge-Weber syndrome

Answer

Turcot syndrome

Answer

Von Hippel-Lindau disease

Question 3

Which of the following is NOT a feature of Netherton Syndrome?

Accepted Answer

Autosomal dominant inheritance

Answer

Ichthyosis

Answer

Very short hair

Answer

Erythroderma

Question 4

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

Accepted Answer

Incontinentia pigmentosa

Answer

Dearth's disease

Answer

Congenital nevus

Answer

Ichthyosis

Question 5

All of the following are seen in Neurofibromatosis, except?

Accepted Answer

Shagreen patch

Answer

Lisch nodules

Answer

Axillary freckling

Answer

Cafe-au-lait spots

Pediatric Dermatology — MCQs

Pediatric Dermatology — MCQs

On this page

Practice by Chapter

Want unlimited practice?