Differentials
Inborn errors of tetrahydrobiopterin or recycling
SIGNS / SYMPTOMS
Hyper-phenylalaninaemia can also result from rare defects in the BH4 pathway. If untreated, these patients could develop intellectual disability, movement disorders, seizures, and other neurological symptoms despite control of blood phenylalanine (phe) level.[9] Much less common than PKU.
INVESTIGATIONS
Urine neopterin to biopterin ratio will be increased in defects of biopterin synthesis.
Dihydropteridine reductase (DHPR) assay will be low in patients with DHPR deficiency.
Hepatic dysfunction
SIGNS / SYMPTOMS
May have hepatomegaly, jaundice.
INVESTIGATIONS
Liver function tests will be abnormal.
Usually multiple elevations of plasma amino acids will be noted, not just phe.
Extreme prematurity
SIGNS / SYMPTOMS
Baby will typically be in neonatal intensive unit. Small size and history of premature delivery.
INVESTIGATIONS
Usually multiple elevations of plasma amino acids will be noted, not just phe.
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