Maria is an 8-year-old girl with Down syndrome, described by her mother as an affectionate and social child, who was referred to developmental-behavioral pediatrics by her pediatrician because of increasing aggressive behaviors and inattention.

Maria was 5 pounds at birth, delivered full-term by cesarean section, and hospitalized for 1 month after delivery because of feeding issues that required a nasogastric (NG) tube. Maternal age was 24 years, pregnancy was uncomplicated, and there were no reported prenatal exposures to substances. Additional medical history includes corrective cardiac surgery at age 11 months, mild-to-moderate hearing loss in 1 ear, and myopia.

At the time of Maria's presentation to developmental-behavioral pediatrics, she was in third grade and had an IEP with placement in a substantially separate multigrade classroom and inclusion for special classes such as music and art. She had multiple academic goals and accommodations for behaviors such as eloping from class, shoving, and growling at adults; communication Picture Exchange Communication System (PECS); and extended time to complete assignments. Previously, she had attended an inclusion setting with a 1:1 aide. Maria is followed annually at a specialty clinic that focuses on the health needs of children with Down syndrome. At home, Maria's parents speak primarily Spanish, while her 2 older brothers speak primarily English. Maria has been using 3-word phrases since she was 6 years old and understands some American Sign Language. She also uses a PECS book for communication.

During the visit, Maria was notably fidgety, frequently interrupted the parent interview despite having toys to play with, and became aggressive—hitting, kicking, pushing, and shoving—when she did not want to comply with directives. She used mostly single words and a variety of gestures to communicate. Both the parent-completed and teacher-completed Conners-3 (Long Version) produced elevated T-scores (>70) in the domains of inattention, hyperactivity/impulsivity, defiance/aggression, peer relations, Global Index scale, DSM-5 Hyperactive/Impulsive symptom scale, and DSM-5 Conduct Disorder symptom scale. The teacher endorsed full criteria for attention-deficit/hyperactivity disorder, consistent with combined presentation, and the parent endorsed symptoms in a similar pattern. Methylphenidate (2.5 mg) was trialed but tolerated poorly when it was titrated to 5 mg. Maria's mother reported that Maria's focus was somewhat better, but she was easily brought to tears and “not herself.”

What would be the next steps in Maria's evaluation/treatment? Could there be reasons for her worsening behavior other than a primary attention disorder?