Ring Chromosome 14 Syndrome MCQ — NEET PG Practice Question | NEETPGAI
Ring Chromosome 14 Syndrome
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smile Pediatrics
A 4-year-old girl presents with intractable seizures since 6 months of age, profound intellectual disability, and microcephaly (OFC <3rd centile). Examination reveals characteristic dysmorphism with high forehead, broad nasal bridge, and long philtrum. Ophthalmologic evaluation shows retinal pigmentary abnormalities. EEG demonstrates multifocal epileptiform discharges with diffuse background slowing. Karyotype analysis reveals the chromosomal abnormality marked as **A** in the diagram. Which of the following best explains the pathophysiology of this condition?
A. Loss of telomeric ends with fusion of broken chromosome ends creating a ring structure that undergoes sister-chromatid exchange and breakage during mitosis, producing chromosomal mosaicism
B. Microdeletion of chromosome 22q11.2 region causing DiGeorge syndrome with cardiac and immunologic manifestations
C. Deletion of the long arm of chromosome 20 with characteristic EEG pattern of long-runs of slow waves and later-onset seizures
D. Interstitial deletion of chromosome 15q11–13 region resulting in loss of paternal gene expression and characteristic behavioral phenotype
Explanation
Why Loss of telomeric ends with fusion of broken chromosome ends creating a ring structure that undergoes sister-chromatid exchange and breakage during mitosis, producing chromosomal mosaicism is right
The karyotype marked A is 46,XX,r(14)(p11.2q32.3), representing Ring Chromosome 14 Syndrome. Ring chromosomes form when both telomeric ends of a chromosome are lost and the broken ends fuse to create a circular structure. The ring is structurally unstable during mitosis—sister-chromatid exchange and breakage events create secondary aneuploidies and chromosomal mosaicism, which accounts for the variable phenotypic severity and the characteristic triad of early-onset intractable epilepsy, intellectual disability, and microcephaly with retinal pigmentary abnormalities (Orphanet — Ring 14 syndrome). Loss of distal 14q telomeric region containing IGF1R and developmental genes drives the clinical phenotype.
Why each distractor is wrong
Deletion of the long arm of chromosome 20 with characteristic EEG pattern of long-runs of slow waves and later-onset seizures: This describes Ring Chromosome 20 Syndrome (marked B in the diagram), which presents with later-onset seizures and a distinctive EEG pattern of long-runs of slow waves—not the early-onset intractable epilepsy seen in this patient.
Interstitial deletion of chromosome 15q11–13 region resulting in loss of paternal gene expression and characteristic behavioral phenotype: This describes Angelman Syndrome (marked C in the diagram), which presents with a characteristic behavioral phenotype including inappropriate laughter, ataxia, and seizures—not the dysmorphic features and retinal pigmentary abnormalities of Ring 14.
Microdeletion of chromosome 22q11.2 region causing DiGeorge syndrome with cardiac and immunologic manifestations: This describes the 22q11.2 deletion (marked D in the diagram), which presents with cardiac defects, immunodeficiency, and cleft palate—not the characteristic retinal findings and specific dysmorphic features of Ring 14.
High-YieldNEET PG
Ring Chromosome 14 = early-onset intractable epilepsy + intellectual disability + microcephaly + retinal pigmentary abnormalities; ring instability during mitosis creates mosaicism and variable severity.
Orphanet — Ring 14 syndrome
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