A 6-year-old boy is brought to your practice by his paternal grandmother for his first visit. She has recently received custody of him after his mother entered the penal system in another state; she does not have much information about him. You note that the child is short for his age, has downslanting palpebral fissures, ptosis, low-set and malformed ears, a broad and webbed neck, shield chest, and cryptorchidism. You hear a systolic ejection murmur in the pulmonic region. His grandmother reports that he does well in regular classes but has been diagnosed with learning disabilities and receives speech therapy for language delay. His constellation of symptoms is suggestive of which of the following?
a) Fetal alcohol syndrome
b) Down syndrome
c) Turner syndrome
d) Williams syndrome