Phenylketonuria have first described by Norwegian Doctor Ivar Asbjörn Fölling in year 1934. Phenylalanine hydroxylase enzyme insufficiency is the main problem. This enzyme will catalysed phenylalanine amino acid to tyrosine. For this reason, in deficiency of this enzym, phenylalanine level will increase in blood and will accumilate in whole body. This disease is a rare disease that have reported in 1 of 10.000 people.
This disease is an autosomal recessive disorder. The cause of this disease is the mutation in phenylalanine hydroxylase (PAH) gene that have localised on chromosome 12. Because of autosomal recessive disorder this disease is more common in consanguineous marriage. The patient will inherit two mutated gene from both parents. Because of it, both of the parents must carry the diseased gene, if a children is affected. %50 percent the child will inheriting only one abnormal gene and will only carrier without being diseased. In %25 chance the child will inherit both of abnormal genes and will have this disease also. The other %25 part, will not carry the diseased genes.
Children with phenylketonuria will appear normal at birth. In untreated infants, 3 to 6 months after the birth the symptoms will start also. They will begin to lose their interest to their surroundings. After 1 years from birth, growth retardation may seen also and the babies skin and hair will impair the color due to pigmentation loss. Then after, this patients will develop some severe intellectual and developmental problems.
These patients will also develop behavioral and social problems too. They will have some seizures also. In movement shaking or jerking on arms and legs may seen too. Microcephaly is common in untreated patients. Light colored skin and blue eyes may seen because of transformation defect from phenylalanine to melanin. These patients will have irregular motor functioning and attention deficit hyperactivity too. Eczematous skin findings will seen due to phenylalanine accumulation in the skin. Diagnosing this disease is easy when suspected. Blood phenylalanine level will elevated over 10 mg/dL.
The main treatment is to prevent to eat or drink phenylalanine containing foods. This patients may eat special diet that have limited phenylalanine contain. In infancy period the best food is breast milk for this patients. In infancy period phenylketonuria formulas are available for this patient’s also. High protein containing foods will contain high phenylalanine. In these patients high protein meals should be avoided too. Chicken and egg, cheese, nuts, soybeans, beans, beef, pork and fish is containing high level of protein so phenylketonuria patients must avoid from this foods. Limit to feed with potatoes, grains and other vegetables with high protein levels also. Sapropterin is a medication for increase the tolerance to phenylalanine in adults.
The mean life expectancy in untreated patients is about 60 years. With a strict diet these patients will live like a normal people. The main problem in untreated persons is developing mental and physical impairments.