Copper toxicosis in the Bedlington terrier: a diagnostic dilemma

Diagnosis of copper toxicosis (CT) in Bedlington terriers by the quantitati ve and qualitative assessment of copper (Cu) in, and pathology of, biopsies has been largely superseded by a DNA-based assay which uses a microsatelli te marker (CO4107) linked to the CT disease allele, A retrospective study w as conducted comprising 154 liver biopsies from Bedlington terriers with 22 matched DNA markers to compare the two methods in the diagnosis of CT. For the biopsy method, three categories (phenotypes) were identified based on analytical and morphological criteria: 'unaffected' in 83 samples (54 per c ent), where Cu was much less than 400 mug/g, and there was an absence of vi sual Cu or liver damage; 'intermediate' in 18 samples (12 per cent), where Cu was less than 400 mug/g, and there was limited histochemical Cu and no/e quivocal damage; and 'affected' In 53 samples (34 per cent), where Cu was g reater than 400 mug/g, there was histochemical Cu and liver damage was poor ly related to Cu content, In the DNA assay, which was used alone on unrelat ed individuals, the microsatellite marker failed to identify the CT status of any of the groups, Liver biopsy remains a reliable Indicator of Cu accum ulation and progressive liver disease In individual dogs, The microsatellit e marker CO4107 has a predictive value only when supported by a pedigree.