Genetic Skin Disorders in Children — MCQs
A 40 year old male reported with recurrent episodes of oral ulcers, large areas of denuded skin and flaccid vesiculo-bullous eruptions. Which is the most important bedside investigation helpful in establishing the diagnosis -
All of the following diseases cause intraepidermal bullae except:
A patient has multiple meningiomas, acoustic neuroma and hyperpigmented skin lesions; most likely diagnosis is –
Baby born with membrane around him at the time of birth. Which of the following conditions is depicted?
What condition is suggested by eyelid papules and a hoarse cry in a child?
A 5-month-old child presented to the dermatology OPD with dryness along with white, fine scales on most parts of the body with sparing of face. The child was born at 39 weeks gestation by spontaneous vaginal delivery outside the hospital. On examination, fine, white scales were observed predominantly on the extensor surfaces of the limbs along with characteristic hyperlinearity of palms and accentuation of skin markings. Which of the following genes is most likely defective in the above condition:
Which of the following is a sign of severe dehydration in a child?
Molluscum contagiosum is caused by a:
In a family with autosomal dominant inheritance, the female parent is affected and the male parent is not affected. What is the chance that their children will be affected?
An 8-year-old girl has extreme photosensitivity since birth. She has recently been diagnosed with skin cancer. What is the diagnosis?
Genetic Skin Disorders in Children Indian Medical PG Practice Questions and MCQs
Question 1: A 40 year old male reported with recurrent episodes of oral ulcers, large areas of denuded skin and flaccid vesiculo-bullous eruptions. Which is the most important bedside investigation helpful in establishing the diagnosis -
- A. Tzanck smear from the floor of bulla (Correct Answer)
- B. Gram staining of blister fluid
- C. Culture and sensitivity of blister fluid
- D. Skin biopsy with immunofluorescence
Explanation: ***Tzanck smear from the floor of bulla*** - A Tzanck smear from the floor of a bulla will reveal **acantholytic cells** (rounded keratinocytes that have lost their intercellular connections), which are characteristic of pemphigus, consistent with recurrent oral ulcers, denuded skin, and flaccid vesiculobullous eruptions. - This **bedside test** provides a rapid diagnosis by demonstrating the cytological features of acantholysis, differentiating it from other blistering disorders. *Gram staining of blister fluid* - This test is primarily used to identify **bacterial infections** and would show the morphology and Gram-staining characteristics of any bacteria present. - It would not provide information about the **acantholysis** or autoimmune nature of the blistering condition described. *Culture and sensitivity of blister fluid* - This investigation identifies **specific bacterial pathogens** and their antibiotic susceptibilities, which is useful for treating bacterial infections. - It would not help in diagnosing **autoimmune blistering diseases** like pemphigus, where bacteria are not the primary cause of the lesions. *Skin biopsy with immunofluorescence* - While a **skin biopsy with direct immunofluorescence** is the gold standard for confirming pemphigus by detecting autoantibodies, it is an **invasive procedure** requiring laboratory processing and is not considered a rapid bedside investigation. - The question specifically asks for the "most important **bed-side investigation**" helpful in establishing the diagnosis rapidly.
Question 2: All of the following diseases cause intraepidermal bullae except:
- A. Miliaria rubra
- B. Herpes gestationalis (Correct Answer)
- C. Herpes zoster
- D. Pemphigus
Explanation: ***Herpes gestationalis.*** - Herpes gestationalis is characterized by **urticarial papules** and vesicles, typically occurs in pregnancy, and does not form **intraepidermal bullae**. - This condition is linked more with **dermatitis herpetiformis** rather than with the intraepidermal blistering seen in the other options [2]. *Herpes zoster* - Herpes zoster causes **vesicular lesions** that are often grouped, presenting as painful **erythematous vesicles** along a dermatome. - The lesions can form intraepidermal bullae due to the **varicella-zoster virus** affecting the skin [1]. *Miliaria rubra* - Miliaria rubra, or **heat rash**, results from occluded sweat glands leading to **superficial vesicles or papules** in the epidermis. - The lesions may resemble blisters but are not true intraepidermal bullae and are prominent in hot, humid conditions. *Pemphigus* - Pemphigus is an autoimmune disorder causing **flaccid bullae** due to **acantholysis** in the epidermis, leading to intraepidermal bulla formation [3]. - It is characterized by **painful, fragile blisters** that rupture easily, differentiating it from other conditions listed [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, p. 366. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1172-1174. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1170-1172.
Question 3: A patient has multiple meningiomas, acoustic neuroma and hyperpigmented skin lesions; most likely diagnosis is –
- A. Neurofibromatosis (Correct Answer)
- B. Von Hippel lindau disease
- C. Sturge weber syndrome
- D. Tuberous sclerosis
Explanation: ***Neurofibromatosis*** - The combination of **multiple meningiomas**, **acoustic neuroma** (specifically bilateral in NF2) [1], and **hyperpigmented skin lesions** (cafe-au-lait spots in NF1, or multiple cutaneous neurofibromas) is highly characteristic of neurofibromatosis. - This presentation suggests either **Neurofibromatosis type 1 (NF1)** with meningiomas (less common but possible) or, more strongly, **Neurofibromatosis type 2 (NF2)** due to the bilateral acoustic neuromas and the presence of meningiomas, with hyperpigmentation being a variable feature [1]. *Von Hippel-Lindau disease* - This disorder is characterized by **hemangioblastomas** of the retina and central nervous system, **renal cell carcinoma**, and **pheochromocytomas**. - It does not typically involve meningiomas, acoustic neuromas, or hyperpigmented skin lesions. *Sturge-Weber syndrome* - This is a neurocutaneous disorder featuring a **port-wine stain (facial nevus flammeus)**, leptomeningeal angioma, and **glaucoma**. - The clinical picture of meningiomas, acoustic neuroma, and hyperpigmented skin lesions does not align with Sturge-Weber syndrome. *Tuberous sclerosis* - This condition is characterized by the growth of numerous **benign tumors in many different organs**, including the brain (tubers, subependymal giant cell astrocytomas), skin (facial angiofibromas, shagreen patches, ash-leaf spots), kidneys (angiomyolipomas), and heart (rhabdomyomas). - While it has **skin lesions** and **brain tumors**, these are distinct from meningiomas and acoustic neuromas, which are not typical features.
Question 4: Baby born with membrane around him at the time of birth. Which of the following conditions is depicted?
- A. X-linked ichthyosis (steroid sulfatase deficiency)
- B. Generalized hyperkeratosis (thickened skin)
- C. Ichthyosis vulgaris (dry, scaly skin)
- D. Lamellar ichthyosis (collodion membrane at birth) (Correct Answer)
Explanation: ***Lamellar ichthyosis (collodion membrane at birth)*** - This condition is characterized by a "collodion membrane" at birth, which is a **tight, shiny, parchment-like membrane** that covers the entire body. - The membrane typically **sheds within weeks**, revealing underlying scaling and erythema characteristic of lamellar ichthyosis. *X-linked ichthyosis (steroid sulfatase deficiency)* - Marked by **dark brown, adherent scales**, primarily affecting the neck, trunk, and extensor surfaces. - It usually becomes apparent **several weeks or months after birth** and is not typically associated with a collodion membrane. *Generalized hyperkeratosis (thickened skin)* - This is a general term for **thickening of the outermost layer of the epidermis** and is a feature of many ichthyoses, not a specific condition with a "membrane at birth." - It describes a **symptom** rather than a primary diagnosis presenting with a specific birth membrane. *Ichthyosis vulgaris (dry, scaly skin)* - Presents with **fine, white scaling**, most prominent on the extensor surfaces of the limbs, but it **rarely appears at birth**. - It is typically **mild** and often worsens in dry, cold weather, lacking the characteristic "membrane around him" at birth.
Question 5: What condition is suggested by eyelid papules and a hoarse cry in a child?
- A. Croup
- B. Lipoid proteinosis (Correct Answer)
- C. Acrodermatitis enteropathica
- D. Congenital syphilis
Explanation: ***Lipoid proteinosis*** - This condition is characterized by **hoarseness from infancy** due to deposition in the vocal cords and characteristic **beaded papules on the eyelids** (moniliform blepharosis). - Also known as **Urbach-Wiethe disease**, it is a rare autosomal recessive disorder resulting from mutations in the **ECM1 gene**, leading to abnormal deposition of hyaline material in various tissues. *Croup* - Croup typically presents with a **barking cough** and **stridor**, often following a viral upper respiratory infection. - It does not cause eyelid papules or chronic hoarseness from infancy, but rather acute respiratory distress. *Acrodermatitis enteropathica* - This is a rare autosomal recessive disorder of **zinc malabsorption**, leading to a classic triad of **dermatitis**, **diarrhea**, and **alopecia**. - It does not involve eyelid papules or hoarseness as primary features. *Congenital syphilis* - Congenital syphilis can cause a wide range of manifestations, including skin rashes, bone abnormalities, and rhinitis ("snuffles"), but eyelid papules and chronic hoarseness are not typical presenting features. - Diagnosis is usually confirmed by serological tests for syphilis.
Question 6: A 5-month-old child presented to the dermatology OPD with dryness along with white, fine scales on most parts of the body with sparing of face. The child was born at 39 weeks gestation by spontaneous vaginal delivery outside the hospital. On examination, fine, white scales were observed predominantly on the extensor surfaces of the limbs along with characteristic hyperlinearity of palms and accentuation of skin markings. Which of the following genes is most likely defective in the above condition:
- A. Filaggrin (Correct Answer)
- B. Desmoglein
- C. Plakophilin
- D. Plakoglobin
Explanation: ***Filaggrin*** - The clinical description of **fine, white scales**, **facial sparing**, **extensor surface involvement**, and **palmar hyperlinearity** is classic for **ichthyosis vulgaris**, the most common inherited disorder of keratinization. - **Filaggrin (FLG)** gene mutations are the most common cause of ichthyosis vulgaris, leading to impaired formation of the skin barrier and loss of natural moisturizing factor. - Typically presents between 3-12 months of age with xerosis and fine scaling. - Key features include **facial sparing**, **flexural sparing**, and **prominent palmar/plantar markings**. *Desmoglein* - **Desmoglein 1** and **Desmoglein 3** are desmosomal cadherins associated with **pemphigus** (autoimmune blistering disorder). - Desmoglein mutations do not cause ichthyotic scaling disorders. - The clinical presentation of fine scaling with facial sparing is not consistent with pemphigus or other desmoglein-related conditions. *Plakophilin* - **Plakophilin-1** mutations cause **ectodermal dysplasia-skin fragility syndrome**, characterized by skin erosions, blistering, alopecia, and nail dystrophy. - Does not present with generalized dry scaling or the pattern described in this case. - Skin fragility and erosions are the hallmark, not ichthyosis. *Plakoglobin* - **Plakoglobin (JUP gene)** mutations cause **Naxos disease**, featuring the triad of arrhythmogenic right ventricular cardiomyopathy, woolly hair, and palmoplantar keratoderma. - While palmoplantar involvement occurs, it is a focal keratoderma, not generalized fine scaling with facial sparing. - Cardiac manifestations are the most serious feature of this condition.
Question 7: Which of the following is a sign of severe dehydration in a child?
- A. Sunken eyes (Correct Answer)
- B. Normal skin turgor
- C. Increased urine output
- D. Moist mucous membranes
Explanation: ***Sunken eyes*** - **Sunken eyes** are a classic sign of significant fluid loss, indicating a depletion of interstitial fluid around the eyes. - This finding is a strong indicator of **moderate to severe dehydration** in children, along with other signs like absent tears and dry mucous membranes. *Normal skin turgor* - **Normal skin turgor** means the skin returns quickly to its original position after being pinched, which is characteristic of adequate hydration. - In dehydration, skin turgor is usually **decreased**, meaning the skin will tent or recoil slowly. *Increased urine output* - **Increased urine output** is a sign of adequate hydration and proper kidney function, as the kidneys are able to excrete excess fluid. - In severe dehydration, the body conserves fluid, leading to significantly **decreased urine output** (oliguria) or no urine output (anuria). *Moist mucous membranes* - **Moist mucous membranes** (e.g., in the mouth or nose) indicate sufficient hydration, as the body can maintain secretions. - In dehydration, especially severe cases, mucous membranes become **dry and sticky** due to reduced fluid volume.
Question 8: Molluscum contagiosum is caused by a:
- A. Flavi virus
- B. Adenovirus
- C. Rubivirus
- D. Pox virus (Correct Answer)
Explanation: ***Pox virus*** - **Molluscum contagiosum** is a common **cutaneous viral infection** caused by the **Molluscum Contagiosum Virus (MCV)**. - MCV belongs to the **Poxviridae family**, which are known for causing characteristic skin lesions. *Flavi virus* - **Flaviviruses** are a genus of RNA viruses, which cause diseases like **Dengue fever**, **Yellow fever**, and **Zika virus infection**. - They typically cause **systemic illnesses** with fever and rash, rather than localized skin lesions like molluscum contagiosum. *Adenovirus* - **Adenoviruses** are DNA viruses primarily associated with **respiratory infections** (e.g., common cold, bronchitis) and **conjunctivitis**. - They are not known to cause the characteristic **umbilicated papules** seen in molluscum contagiosum. *Rubivirus* - **Rubivirus** is a genus that includes the **Rubella virus**, which causes **German measles** (Rubella). - Rubella is characterized by a **maculopapular rash** and **lymphadenopathy**, which is distinct from the **umbilicated papules** seen in molluscum contagiosum.
Question 9: In a family with autosomal dominant inheritance, the female parent is affected and the male parent is not affected. What is the chance that their children will be affected?
- A. All affected
- B. 50% affected (Correct Answer)
- C. 75% affected
- D. 25% affected
Explanation: ***50% affected*** - In **autosomal dominant** inheritance, only one copy of the altered gene is needed to cause the disorder. If an affected parent (carrying one normal and one altered gene, Aa) mates with an unaffected parent (carrying two normal genes, aa), there is a 50% chance for each child to inherit the altered gene (Aa) and thus be affected. - This outcome results from a **Punnett square** analysis: Parent 1 (Aa) and Parent 2 (aa) yield offspring genotypes of Aa, Aa, aa, and aa. *All affected* - This scenario would only occur if both parents were homozygous dominant (AA x aa) or if one parent were homozygous dominant and the other heterozygous (AA x Aa), which is not the case described. - If a condition is 100% penetrant and both parents are affected, or at least one is homozygous dominant, then all children could potentially be affected. *75% affected* - This probability typically occurs when both parents are **heterozygous** for an autosomal dominant trait (Aa x Aa), resulting in a 75% chance of affected offspring (AA, Aa, Aa, aa). - The given condition is that only one parent is affected, ruling out this probability. *25% affected* - This percentage is characteristic of **autosomal recessive** inheritance when two heterozygous carriers (Aa x Aa) mate, resulting in a 25% chance of affected offspring (aa). - Since the inheritance pattern is autosomal dominant, this probability is not applicable.
Question 10: An 8-year-old girl has extreme photosensitivity since birth. She has recently been diagnosed with skin cancer. What is the diagnosis?
- A. Xeroderma Pigmentosum (Correct Answer)
- B. Bloom syndrome
- C. Griscelli syndrome
- D. Chediak Higashi syndrome
Explanation: ***Xeroderma Pigmentosum*** - This condition is characterized by an extreme sensitivity to **ultraviolet (UV) light** from birth due to defects in **DNA repair mechanisms**, leading to severe sunburns, pigmentary changes (freckles, hypopigmented macules), and a high risk of developing **skin cancers** at a young age. - The history of extreme photosensitivity since birth and the diagnosis of skin cancer in an 8-year-old girl is highly indicative of Xeroderma Pigmentosum. *Bloom syndrome* - Bloom syndrome is an inherited disorder characterized by **stunted growth**, a **photosensitive facial rash (telangiectatic erythema)**, and a predisposition to **various cancers**, including leukemia and lymphomas. - While photosensitivity and cancer risk are present, the extreme skin damage and early onset of specific skin cancers (as opposed to leukemias/lymphomas often seen in Bloom) make Xeroderma Pigmentosum a more fitting diagnosis. *Griscelli syndrome* - Griscelli syndrome is a rare autosomal recessive disorder characterized by **partial albinism**, immunodeficiency, and neurological impairment. - While it involves pigmentary abnormalities, it does not typically present with the extreme photosensitivity or the very early skin cancer development described in the patient. *Chediak Higashi syndrome* - Chediak-Higashi syndrome is an autosomal recessive disorder characterized by **partial albinism**, recurrent pyogenic infections, and neurological abnormalities, due to defective lysosomal trafficking. - This syndrome is not primarily associated with extreme photosensitivity leading to early skin cancers but rather with immunodeficiency and neurological issues.
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