Background: Molybdenum cofactor deficiency (resulting in combined
deficiencies of the enzymes sulphite oxidase, xanthine dehydrogenase and aldehyde
dehydrogenase) and isolated sulphite oxidase deficiency are inherited metabolic
diseases which follow an autosomal recessive trait of inheritance. Detection of these
diseases in selective screening for inborn errors of metabolism is not easy because
relevant metabolites are either not routinely determined or are unstable.
Methods: We have searched for additional markers for these diseases and
studied plasma total homocysteine (determined by enzyme immunoassay) and
S-sulphonation of transthyretin (assessed by electrospray
ionization mass spectrometry).
Results and conclusion: We found total homocysteine concentrations below
the limit of quantification (<1 µmol/L) in all samples of
patients with sulphite oxidase deficiency studied in this regard and that the
proportion of S-sulphonated transthyretin is clearly increased in
such samples. Our observations suggest additional tools for selective screening and
diagnostic work-up of patients suspected of having sulphite oxidase deficiency.
