Snapshot A 6-year-old boy is brought to the pediatrician for a well child visit. The mother reports that the patient has been otherwise well; however, she has noticed that he has had multiple middle ear infections. He has been having some learning difficulty in school. On physical examination, the patient has widely spaced teeth, prominent ear lobes, and a short nose with full nasal tip. He is also overly friendly and has a systolic murmur in the aortic region. (Williams syndrome) Cri-Du-Chat Syndrome (5p Deletion Syndrome) Clinical definition a structural chromosomal defect secondary to a microdeletion of the short arm of chromosome 5p Pathogenesis most cases (~85%) are due to de novo partial deletions of chromosome 5p (the short arm) the rest is caused by parental translocation of 5p Clinical presentation mew-like cry early in life cri-du-chat means cry of the cat low birth weight intellectual disability hypotonia microcephaly hypertelorism cardiac abrnomalities (e.g., ventricular septal defect) Williams Syndrome Clinical definition a genetic disorder secondary to a deletion of a region on chromosome 7 Pathogenesis deletion of a chromosomal region that includes the elastin gene on chromosome 7 Clinical presentation appearance "elfin" facies cognitive involvement mental retardation (typically mild) personality overfriendly very empathetic anxiety problems with attention cardiac may find murmur secondary to aortic stenosis (supravalvular aortic stenosis) other findings idiopathic hypercalcemia 22q11 Microdeletions Clinical definition a genetic disorder secondary to a microdeletion at the 22q11 chromosome that can result in Cleft palate Abnormal facies Thymic aplasia which results in T-cell deficiency Cardiac defects Hypocalcemia secondary to parathyroid aplasia mnemonic = CATCH-22 Specific 22q11 microdeletion syndromes DiGeorge syndrome abnormalities in the development of the 3rd and 4th branchial pouches resulting in hypoplasia of the thymus hypoplasia of the parathyroid cardiac defects facial dysmorphism therefore patients can present with increase susceptibility to infection hypocalcemia congenital heart disease velocardiofacial syndrome has overlap with DiGeorge syndrome patients typically present with retrognathia long face with prominent nose velopharyngeal incompetence leading to hypernasal speech chronic otitis media transient neonatal hypocalcemia in certain cases congenital heart defects (ventricular septal defects is most common) learning disability