What is hyperphenylalaninemia? what causes it?

A genetic disease: Hyperphenylalanemia (non-PKU) is a genetic inherited disease. Usually each parent has a mutation in the metabolism of amino acid, phenylalanine. Both parents do not necessarily have an identical mutation. This condition is also usually picked up by newborn screening. Affected child must be carefully followed up by a specialist, since the patient needs a special formula devoid of phenyhlalanine.