Genodermatoses and Rare Disorders MCQs

Dermatology · 30 free questions with answers & explanations.

1. A newborn presents with a collodion-like membrane at birth that cracks and peels over weeks. The child subsequently develops thick, generalized, dark-brown, plate-like scales with no blistering. The condition is non-inflammatory and inherited. What is the diagnosis?
2. A child presents with generalized ichthyosis, recurrent skin infections, photophobia, and oculocutaneous albinism. Peripheral blood smear shows giant granules in neutrophils. What is the gene mutated in this disorder?
3. A newborn is delivered encased in a tight, shiny 'collodion membrane' that cracks and peels within weeks. The most likely underlying diagnosis is:
4. Darier's disease (keratosis follicularis) is caused by mutation in ATP2A2 gene encoding SERCA2 (sarco/endoplasmic reticulum Ca2+-ATPase). The hallmark histological feature is:
5. Xeroderma pigmentosum results from defective nucleotide excision repair (NER). Which of the following clinical associations and complementation groups is correctly paired?
6. A 2-year-old child presents with hyperkeratotic plaques over joints, palmoplantar keratoderma, and ichthyosis. Electron microscopy of the skin shows abnormal tonofilament aggregates within keratinocytes. The most likely diagnosis is:
7. In Darier's disease (keratosis follicularis), the histopathological finding of 'corps ronds' and 'grains' are pathognomonic. Corps ronds are found in:
8. A 10-year-old child has multiple café-au-lait spots (>6, >5 mm diameter), axillary freckling, and bilateral optic nerve gliomas. This is neurofibromatosis type 1 (NF1). The NF1 gene product neurofibromin functions as:
9. Hailey-Hailey disease (familial benign chronic pemphigus) is caused by mutation in which gene, and what is the main histopathological difference from pemphigus vulgaris?
10. A newborn presents with severe generalized skin fragility and blistering immediately after birth. Electron microscopy shows absent anchoring fibrils at the dermoepidermal junction. Immunofluorescence mapping shows absent type VII collagen. The most likely diagnosis and its inheritance pattern are:
11. Xeroderma pigmentosum (XP) is caused by defective nucleotide excision repair (NER). Which XP complementation group has the highest cancer risk and is also associated with neurological manifestations?
12. A neonate is born encased in a tight, parchment-like collodion membrane. After shedding, she develops widespread non-inflammatory scaling. Genetic testing reveals a mutation in TGM1 gene. The most likely diagnosis is:
13. A 3-year-old boy presents with diffuse scaling, sparse hair, photophobia, and intellectual disability. His urine shows elevated 7-dehydrocholesterol. He has mutations in the CHILD syndrome-related pathway. The condition affecting cornified envelope cross-linking along with sterol metabolism is:
14. A boy has recurrent skin fragility, oral erosions, and milia since birth. Electron microscopy of the skin shows cleavage within the basal keratinocytes (cytolysis of basal cells). The defective protein and inheritance are:
15. Darier disease (keratosis follicularis) shows characteristic histopathological features. Which of the following is the MOST pathognomonic finding on skin biopsy?
16. Incontinentia pigmenti (Bloch-Sulzberger syndrome) follows which inheritance pattern, and what is the molecular defect?
17. A 20-year-old patient has multiple café-au-lait macules, axillary freckling, Lisch nodules, and neurofibromata. He is at highest risk for which internal malignancy?
18. A child presents with recurrent blistering after minor trauma since birth. There is no family history. Electron microscopy shows blistering within the lamina lucida. The molecular defect is most likely in:
19. Xeroderma pigmentosum (XP) results from a defect in nucleotide excision repair. Which specific XP complementation group is associated with the most severe neurological involvement (De Sanctis-Cacchione syndrome)?
20. A newborn is encased in a tight, shiny, plate-like membrane that cracks at flexures. After shedding, the child develops widespread ichthyosis. Mutation in TGM1 gene (encoding transglutaminase 1) is identified. The diagnosis is:
21. A 20-year-old male presents with multiple flesh-coloured papules over the trunk and neck. His father has the same lesions. Ophthalmology shows angioid streaks. Cardiovascular examination reveals peripheral arterial calcification. The gene mutated is:
22. Incontinentia pigmenti (Bloch-Sulzberger syndrome) has all of the following features EXCEPT:
23. A 6-month-old infant presents with large areas of eroded skin from birth, with blistering on minimal friction. EM shows absent hemidesmosomes and no anchoring fibrils. The gene mutation is in:
24. A 4-year-old boy with xeroderma pigmentosum (XP) group A develops progressive neurological deterioration. The underlying molecular defect responsible for both the cutaneous and neurological features is:
25. A child born to consanguineous parents has large yellowish-brown scales over the entire body since birth. Biopsy shows hyperkeratosis with a normal granular layer. Enzyme assay shows deficiency of steroid sulfatase. The expected inheritance pattern and associated features are:
26. Incontinentia pigmenti (Bloch-Sulzberger syndrome) passes through 4 clinical stages. Which of the following correctly pairs the stage with its histopathological finding?
27. Darier disease (keratosis follicularis) is an autosomal dominant genodermatosis with characteristic greasy crusted papules in seborrhoeic distribution. Its molecular defect is in:
28. Pachyonychia congenita (PC) is a genodermatosis caused by mutations in keratin genes. PC type 1 (Jadassohn-Lewandowsky) involves which keratins and has which hallmark clinical feature?
29. A child presents with recurrent skin blistering at pressure points from birth, healed scars with milia formation, and nail dystrophy. Parents are consanguineous. Biopsy shows cleavage within the lamina lucida (sub-lamina lucida level). Electron microscopy shows hypoplastic hemidesmosomes with absent sub-basal dense plate. The gene mutation responsible for the most severe (lethal) form is:
30. Epidermolysis bullosa simplex (EBS) — the most common inherited EB subtype — is caused by mutations in which structural proteins?