Serum concentrations and urinary excretion of homogentisic acid and tyrosine in normal subjects.

Abstract

Alkaptonuria (AKU) is a rare, inherited metabolic disease of tyrosine metabolism. Degradation of tyrosine is blocked at the level of homogentisic acid (HGA) due to a congenital lack of the enzyme homogentisate 1,2-dioxygenase. Medical management of AKU has been palliative relying largely on analgesia and arthroplasty. With the establishment of a National Alkaptonuria Centre in Liverpool, nitisinone (NTBC), is being prescribed to AKU patients. Monitoring of off-licence therapy is essential for patient safety. NTBC has resulted in a >95% suppression of HGA excretion with a concurrent rise in serum tyrosine (>500 μmol/L). On-going clinical trials as part of the DevelopAKUre program are assessing the dose of NTBC which suppresses HGA to within the normal healthy population reference range. This study was aimed at determining the reference range of HGA and tyrosine in serum and urine, in a non-AKU population.