A 2-day-old term male neonate is brought to the hospital with abdominal distension and bilious vomiting. The baby has not passed meconium since birth. Physical examination reveals a distended abdomen without tenderness. Abdominal X-ray shows dilated loops of bowel with no air in the rectum. Contrast enema reveals a microcolon with inspissated material in the terminal ileum. What is the most likely underlying cause of this neonate’s condition?
