Intellectual impairment after long-term NTBC treatment?

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Treatment of hypertyrosinemia (HT) type I with NTBC can prevent acute liver failure and hepatocellular carcinoma thus improving survival of patients. However, there is some evidence of cognitive impairment in patients with secondary elevated plasma tyrosine levels. Thimm et al. used standardized psychometric test batteries to evaluate the neurocognitive development (cognition, motor abilities and speech) in nine early-treated patients under long-term NTBC treatment. The 12-month median plasma tyrosine concentration was elevated in seven out of nine patients despite NTBC concentrations generally being in the lower therapeutic range.

  • Total IQ score was below average in 5 out of 7 patients
  • Motor abilities were subnormal in 4 out of 7 patients
  • Cerebral MRI revealed no abnormalities
  • Logopedic evaluation demonstrated problems in language development in all but one of the tested patients (80%)


The authors conclude that intellectual impairment may be a long-term complication in HT type I with elevated plasma tyrosine under NTBC treatment as observed in other hypertyrosinemias.  

Neurocognitive outcome in patients with hypertyrosinemia type I after long-term treatment with NTBC. Thimm  et  al. J Inherit Metab Dis. 2012 Mar;35(2):263-8. PMID: 22069142

posted by Yannis Trakadis MD, MSc

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