Chromosomal Deletions

  • Cri-du-chat syndrome
    • Congenital deletion on short arm of chromosome 5 (46,XX or XY, 5p−). Findings: microcephaly, moderate to severe intellectual disability, high-pitched crying/meowing, epicanthal folds, cardiac abnormalities (VSD).
    • Cri du chat = cry of the cat.
  • Williams syndrome
    • Congenital microdeletion of long arm of chromosome 7 (deleted region includes elastin gene).
    • Findings: distinctive “elfin” facies, intellectual disability, hypercalcemia (↑ sensitivity to vitamin D), well-developed verbal skills, extreme friendliness with strangers, cardiovascular problems (eg, supravalvular aortic stenosis, renal artery stenosis). Think Will Ferrell in Elf.
  • 22q11 deletion syndromes
    • Microdeletion at chromosome 22q11 → variable presentations including Cleft palate, Abnormal facies, Thymic aplasia → T-cell deficiency, Cardiac defects (Tetralogy of Fallot, truncus arteriosus, transposition of the great arteries), and Hypocalcemia 2° to parathyroid aplasia. CATCH-22.
    • DiGeorge syndrome—thymic, parathyroid, and cardiac defects.
    • Velocardiofacial syndrome—palate, facial, and cardiac defects.
    • Test: Fluorescence in situ hybridization
    • Due to aberrant neural crest migration of 3rd and 4th branchial (pharyngeal) pouches.

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