Milton has a round face, a broad, flat nose, small, downward sloping folds of skin at the inside corners of his eyes, a protruding tongue, small, squarish hands, and unusually short arms and legs in relation to his body. he suffers from intellectual developmental disorder and from heart and respiratory problems. he most likely has

He is most likely to have down syndrome.

Down syndrome is caused by a mutation of DNA. During cell division of meiosis, the 21st chromosomes failed to separate from each other, and both of the 21st chromosomes enters the same ovum. The ovum gets fertilized and that leads to an extra 21st chromosome presence in Milton. This also means that Milton has 47 chromosomes in his body instead of a normal human with 46.

Down syndrome is one of the most common result from mutation, the permanent change of gene or chromosomes. The rate of mutation increases when radiation (such as X ray or UV lights) or chemicals (such as tar) are absorbed.