Phenylketonuria and Clinical picture

Phenylketonuria

Inheritence: phenylketonuria is inherited as autosomal recessive disease as a result of deficiency of phenylalanine hydroxylase enzyme or its co-factor tetrahydrobiopetrin (BH4 ).

Clinical picture

● Newborn infant with phenylketonuria appear to be clinically normal and the abnormal metabolites may not be excreted in the urine for several weeks.

● When untreated, the disease causes progressive brain damage, microcephaly, hypertonicity, convulsions, dysphasia, hyperactivity with purposeless movement.

                                               

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The skin and hair are often light coloured and the irides may be pale.

● Vomiting may mimic pyloric stenosis.

● There is mousy or musty odour of the urine.

Laboratory findings

- Phenyl  alanine and its metabolites appear in urine.

- Confimatory diagnosis by estimating serum level of phenylalanine hydroxylase enzyme.

Management

- By giving the infant phenylalanine free diet and by oral adiminstration of co-factor tetrahydrobiopetrin.