Though it is years off yet, it is in the making. Those children who get the classic infantile form begin to present symptoms between 2 and 9 months. Later onsets may or may not progress at a similar rate. Early symptoms may include severe crankiness, body or limb rigidity, loss of milestones, severe reflux, seizures, feeding trouble, unexplained fevers, and unusual eye movement. If this enzyme is not there or present in very low concentration, the child is affected.
Prenatal testing is also available.
Some children will decline rapidly while others will stabilize for some time. Each parent will have a different story at this point. In the later stages, children may lose eyesight, hearing and experience paralysis. Prolonged weight loss may also become a problem, as the body doesn't process food as well. The severity or the prevalence of these later symptoms will vary.