Tyrosinaemia type I—de novo mutation in liver tissue suppressing an inborn splicing defect

Many patients with tyrosinaemia type 1 have a mosaic pattern of fumarylacetoacetase (FAH) immunopositive or immunonegative nodules in liver tissue. This phenomenon has been explained by a spontaneous reversion of the mutation in one allele to a normal genotype, but only a few nodules have been examined. We now report on a Norwegian patient, compound heterozygous for the mutations IVS12g+5→a and G1009→A, with liver mosaicism, but with an...