An 8-Year-Old Boy Is Brought to the Office by His

An 8-year-old boy is brought to the office by his mother due to difficulties at school.  The patient was adopted at age 2 from an orphanage.  Medical history is significant for a heart murmur that resolved when he was an infant.  His mother says, "His handwriting is illegible and the school wants to keep him back a grade.  He has always struggled to sit still and focus; he is clumsy and breaks things without meaning to.  He gets upset easily and throws things or hits his brothers when they don't do what he wants."  The patient's teacher has reported that he doesn't listen, talks back, and distracts other children.  Psychoeducational testing revealed an IQ score of 85.  In the office, the boy is playing with a toy.  When his mother takes it away, he hits her, starts crying, and becomes difficult to console.  Vital signs are within normal limits.  Weight and height are tracking at the 30th percentile, but head circumference is below the 10th percentile.  Physical examination shows a thin upper lip and short palpebral fissures.  Which of the following is the most likely diagnosis?

A) Attention-deficit hyperactivity disorder
B) DiGeorge syndrome
C) Down syndrome
D) Fetal alcohol syndrome
E) Fragile X syndrome
F) Oppositional defiant disorder
G) Reactive attachment disorder
H) Velocardiofacial syndrome