Practice question

Cri-du-chat syndrome, or 5p- syndrome, results from terminal deletion of the short arm of chromosome 5. The critical interval at 5p15.2 contains dosage-sensitive genes like CTNND2 involved in neuronal migration. Haploinsufficiency causes cat-like cry in infants due to laryngeal hypoplasia, microcephaly, severe intellectual disability, and distinctive facial dysmorphism. Deletion size correlates with severity but minimal critical region defines syndrome. Most cases are de novo deletions; 10-15% arise from parental balanced translocation. Diagnosis relies on karyotype and FISH or microarray demonstration of 5p loss.