A 2-month-old infant is brought by her parents due to concerns about her development and overall health. The parents express worry over delayed milestones, like slower motor development, limited responsiveness, and weaker muscle tone. She had a full-term delivery without any complications during pregnancy or the postnatal period. She experiences feeding difficulty. There is no known history of genetic disorders in the family. On physical examination, the infant exhibits distinct facial features, including a flattened facial profile, downward-slanting eyes, a small nose, and low-set ears. Hypotonia is also noted. Karyotyping confirms the presence of an extra chromosome 21.