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).

Q: Acrodermatitis enteropathica is a classical presentation due to deficiency of?

Zinc. **Explanation:** **Acrodermatitis Enteropathica (AE)** is an autosomal recessive disorder caused by a mutation in the **SLC39A4 gene**, which encodes the **ZIP4 transporter**. This defect leads to impaired intestinal absorption of **Zinc**. 1. **Why Zinc is Correct:** Zinc is a vital trace element for cell division and protein synthesis. Its deficiency manifests as the classic triad of **periorificial and acral dermatitis** (vesiculobullous or eczematous lesions around the mouth, anus, and limbs), **alopecia**, and **diarrhea**. It typically presents in infants when transitioning from breast milk to formula or solid foods, as breast milk contains a zinc-binding ligand that facilitates absorption. 2. **Why Other Options are Incorrect:** * **Vitamin K:** Deficiency leads to bleeding diathesis (Hemorrhagic Disease of the Newborn) due to decreased synthesis of clotting factors II, VII, IX, and X. * **Copper:** Deficiency (Menkes Kinky Hair Syndrome) presents with "steely" or "kinky" hair, growth failure, and neurological regression, but not periorificial dermatitis. * **Selenium:** Deficiency is associated with **Keshan disease** (cardiomyopathy) and Kashin-Beck disease (osteoarthropathy). **Clinical Pearls for NEET-PG:** * **Classic Triad:** Dermatitis (Acral/Periorificial), Alopecia, and Diarrhea. * **Diagnosis:** Low serum alkaline phosphatase (as it is a zinc-dependent enzyme) and low serum zinc levels. * **Treatment:** Lifelong oral zinc supplementation (elemental zinc 1–3 mg/kg/day). * **Acquired Zinc Deficiency:** Can occur in patients on prolonged Total Parenteral Nutrition (TPN) without trace element supplementation or in malabsorption syndromes.

Q: A 5-year-old male child presents with multiple hyperpigmented macules over the trunk. Upon rubbing the lesions with the rounded end of a pen, urticarial wheals develop, confined to the border of the lesion. What is the most likely diagnosis?

Urticaria pigmentosa. **Explanation:** The clinical presentation describes a classic case of **Urticaria Pigmentosa (UP)**, the most common form of cutaneous mastocytosis in children. **1. Why Urticaria Pigmentosa is correct:** The key to this diagnosis is the positive **Darier’s sign**. When the hyperpigmented macules (caused by an accumulation of mast cells in the dermis) are stroked or rubbed, it triggers mast cell degranulation. This releases inflammatory mediators like histamine, leading to localized edema and erythema (wheal formation) confined strictly to the lesion. In children, these lesions typically appear as reddish-brown macules or papules on the trunk. **2. Why other options are incorrect:** * **Fixed Drug Eruption (FDE):** Presents as a solitary (usually), dusky red/violaceous plaque that recurs at the same site upon drug re-exposure. It does not exhibit Darier’s sign. * **Lichen Planus:** Characterized by the "6 Ps" (Planar, Purple, Polygonal, Pruritic, Papules, and Plaques) and Wickham striae. It shows the **Koebner phenomenon** (lesions at sites of trauma), not Darier’s sign. * **Urticarial Vasculitis:** Presents as wheals that persist for >24 hours and often leave behind post-inflammatory hyperpigmentation. However, these wheals are not triggered by rubbing a pre-existing macule. **Clinical Pearls for NEET-PG:** * **Darier’s Sign:** Pathognomonic for Mastocytosis. * **Pseudo-Darier Sign:** Seen in **Smooth Muscle Hamartoma** (temporary induration/piloerection on rubbing). * **Systemic Mastocytosis:** Suspect if there is hepatosplenomegaly, lymphadenopathy, or systemic symptoms (flushing, diarrhea). * **Treatment:** Primarily symptomatic (H1/H2 blockers); avoid mast cell triggers (NSAIDs, morphine, heat).

Q: All of the following neurocutaneous signs are seen in Neurofibromatosis Type 2, EXCEPT:

Shagreen patch. This question tests the ability to differentiate between the two major neurocutaneous syndromes: **Neurofibromatosis (NF)** and **Tuberous Sclerosis Complex (TSC)**. ### **Explanation of the Correct Answer** **D. Shagreen patch** is the correct answer because it is a pathognomonic feature of **Tuberous Sclerosis**, not Neurofibromatosis. It is a connective tissue nevus, typically appearing as a "leathery" or "orange-peel" textured plaque on the lower back. ### **Analysis of Other Options** * **A. Meningioma:** This is a classic feature of **NF-2**. While NF-1 is characterized by peripheral nerve tumors, NF-2 is characterized by central nervous system tumors, remembered by the mnemonic **MISME** (Multiple Inherited Schwannomas, Meningiomas, and Ependymomas). * **B. Lisch nodule:** These are iris hamartomas. While they are a hallmark diagnostic criterion for **NF-1**, they can occasionally be seen in NF-2 (though much less frequently). In the context of this "Except" question, the Shagreen patch is the most definitive outlier as it belongs to a completely different disease spectrum (TSC). * **C. Axillary freckling (Crowe’s sign):** Similar to Lisch nodules, this is a classic feature of **NF-1**. However, in NEET-PG questions, features of NF-1 and NF-2 are often grouped under the broad umbrella of "Neurofibromatosis" to contrast them against Tuberous Sclerosis. ### **High-Yield Clinical Pearls for NEET-PG** * **NF-2 (Chromosome 22):** Key feature is **Bilateral Acoustic Neuromas** (Vestibular Schwannomas). * **NF-1 (Chromosome 17):** Characterized by Café-au-lait spots, Neurofibromas, and Lisch nodules. * **Tuberous Sclerosis (TSC1/TSC2):** Look for the triad of **Vogt’s (Epiloia)**: Adenoma sebaceum (Angiofibromas), Mental retardation, and Epilepsy. Other signs include Ash-leaf spots and Koenen’s tumors (periungual fibromas).

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

Question 6

Acrodermatitis enteropathica is a classical presentation due to deficiency of?

Accepted Answer

Zinc

Answer

Vitamin K

Answer

Copper

Answer

Selenium

Question 7

A 5-year-old male child presents with multiple hyperpigmented macules over the trunk. Upon rubbing the lesions with the rounded end of a pen, urticarial wheals develop, confined to the border of the lesion. What is the most likely diagnosis?

Accepted Answer

Urticaria pigmentosa

Answer

Fixed drug eruption

Answer

Lichen planus

Answer

Urticarial vasculitis

Question 8

A 20-year-old male with Acute Myeloid Leukemia (AML) is undergoing chemotherapy and has a neutrophil count of 400/mm
3, for which he was started on prophylactic antibiotics. The patient developed a sudden spike of fever and is complaining of severe myalgias, joint pains, and painful, widespread skin lesions. Biopsy of a skin lesion will most likely show what?

Accepted Answer

Disseminated fungal hyphae and yeast

Answer

Intravascular thrombi with coagulative necrosis

Answer

Intracytoplasmic viral inclusions

Answer

Eosinophilic microabscesses

Question 9

Which of the following conditions disappear spontaneously in the first year of life?

Accepted Answer

Salmon patch

Answer

Port wine stain

Answer

Nevus flammeus

Answer

Strawberry hemangioma

Question 10

All of the following neurocutaneous signs are seen in Neurofibromatosis Type 2, EXCEPT:

Accepted Answer

Shagreen patch

Answer

Meningioma

Answer

Lisch nodule

Answer

Axillary freckling

Pediatric Dermatology — MCQs

Pediatric Dermatology — MCQs

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