A 2-Month-Old Kid Is Taken to the Emergency Room Because

A 2-month-old kid is taken to the emergency room because of increased "floppiness" and poor eating. The child was delivered in Eastern Europe to a 38-year-old lady in an uneventful vaginal birth and later relocated to the United States with his family. The parents describe their child as a "excellent baby" who seldom cries and sleeps through the night but has recently been difficult to wake up for nursing. Stool frequency has also been reduced to every other day, and they are tiny and pellet-like. A hypotonic child with a big anterior fontanelle, large tongue, and a reducible umbilical hernia is seen on physical examination. He has a low tone and is unable to stand on his own. There are no additional abnormalities found. Which of the following is the most likely cause of this patient's condition?

A) Botulism
B) Down syndrome
C) Galactosemia
D) Hirschsprung disease
E) Hypothyroidism
F) Phenylketonuria