Tyrosinemia II

Introduction
Tyrosinemia type II is an autosomal recessive condition caused by a defect in the
hepatic tyrosine aminotransferase gene (see figure) responsible for converting tyrosine
to 4-hydroxyphenylpyruvate. It is characterized clinically by eye and skin lesions with
neurological sequelae including developmental delay, behavioral problems and self
injurious behaviors also occurring frequently.

Clinical Features
Neonatal
Photophobia, lacrimation, burning eye pain, infamed conjunctiva
Infancy/childhood
The above plus
Blistering lesions on the palms and soles
Microcephaly
Developmental delay
Behavioral problems
Consequences

Diagnosis
Newborn screen
Tandem mass spectrometry
Confirmation
Repeat newborn screen
Elevated plasma and CSF Tyrosine level
Elevated urinary phenolic acid metabolites
Confirmatory diagnosis is possible via enzyme assay from liver biopsy

Treatment
A low protein or special diet restricting phenylalanine and tyrosine will alleviate failure to
thrive in days, the eye condition in weeks and the skin condition in months. Maintaining
tyrosine levels below 800µmol/l appears to be protective against pathology including
neurological sequelae.

Situations that risk metabolic decompensation
*
Monitoring
Clinical monitoring to ensure that there are no signs of eye, skin or neurological
symptomatology. An opthomological evaluation is required upon diagnosis and regular
follow up thereafter. Signs of developmental delay and behavioral problems should be
carefully screened for. Tyrosine levels should be checked

STAT emergency treatment
*
Infection/Immunization
*
Surgical/surgical procedures
*
Growth and development
As these patients are maintained on a restricted diet it is crucial to closely monitor all
growth parameters on a regular basis. In cases with neurological deficits the child should
be integrated into an early intervention program and developmental progress closely
monitored by both the metabolic team and the primary care provider. It is hoped that
pre-symptomatic identification and treatment of patients with Tyrosinemia type II will
prevent any long-term problems.

Figure