This disease interestingly, occurs in babies as an inherited genetic defect. It prevents the production of a special body hormone called phenylalanine hydroxylase, which in turn makes it impossible for chemicals in certain foods to be dealt with in the body. So they accumulate, and unless treated may cause severe mental retardation.
It seems more likely in blue-eyed blond babies. They may seem normal at birth, but soon after develop vomiting, restlessness and irritability, a peculiar smell, skin rashes and an odd behavior. Sometimes convulsions take place. Mental retardation will occur and intelligence suffers as the child becomes older. Many become hyperactive and their behavior may be erratic. Excessive sweating is also common.
Ideally they are treated from birth with foods that do not contain the chemical phenylalanine. This usually means a restricted diet, especially with milk, or synthetic forms may be used that do not contain the chemical that causes the trouble, and which cannot be dealt with by the system because of the deficiency. This routine may be continued for quite a few years. It is yet undecided at what age it can be discontinued, if ever. Some say a minimum of five years is essential. Others believe it may require care for the rest of life.
A great deal of progress has been made in diagnosis in recent years. It is now a routine for all Australian hospitals to check every baby by performing a blood test at birth. If present, it can be picked up rapidly, and immediate steps taken for correct dietary therapy.
Do many infants suffer from the disorder? Some textbooks claim the figure is about 1 in every 15,000, boys and girls being equally affected. Of the first 2.5 million babies screened in Australia, 222 positives were detected, which means about one case in every 11,000 born. In a recent year, eighteen cases were detected. Screening has made an enormous difference to detecting these cases and is a very worthwhile check. The amount of worry and money saved is almost incalculable.