Answer:
Physical findings of the head: flat occiput, large fontanelles, persistent metopic suture, hypoplastic or absent frontal, sphenoid, and maxillary sinuses, brachycephaly, midface hypoplasia, hypotelorism, flattened nasal bridge, upslanting palpebral fissures and epicanthal folds, small ears, broad irregular lips, relatively large tongue (due to small oral cavity), dental irregularities including missing teeth, hypoplasia, and malalignment.
Associated physical findings: short broad hands, clinodactyly, simian creases, brachydactyly, small genitalia in males, hyperflexible joints.
Genetic mode of transmission: 95% result from nondisjunction during meiotic division of chromosome 21. 5% of cases are a result of translocation, either inherited from a parent or arising de novo.
Mental status: mental retardation considered a hallmark.
Timing of operation: variable, dependent on specific anomaly to be corrected.