Wilson's disease: the importance of measuring serum caeruloplasmin non-immunologically

Wilson's disease should be considered as a possible diagnosis in any child, adolescent or young adult with liver damage without other explanation, especially when haemolysis is present. However, it may also present in adolescents or young adults with neurological signs confined to the motor system. The first diagnostic screening test is the estimation of the serum caeruloplasmin and total serum copper concentrations, with calculation of the serum non-caeruloplasmin-bound ('free') copper. Serum caeruloplasmin, which contains copper, is best determined by measurement of its oxidase activity, as the immunonephelometric method measures both caeruloplasmin and the biologically inactive apo-form. Diagnosis may be confirmed by an elevated urinary copper excretion. All close relatives of an identified patient must be screened and, where doubt persists, investigation of the Wilson's gene at chromosome 13q14.3 can be employed. Lifelong follow-up studies are best conducted in a specialist centre. Compliance with chelating therapy (penicillamine or trientine) or administration of the metal antagonist tetrathiomolybdate or zinc is monitored by determination of the serum 'free' copper, which should be maintained at or near 1.6 micromol/L (10 microg/100 mL). Side-effects of therapy are detected by the estimation of urinary total protein, full blood count and erythrocyte sedimentation rate, clotting factors and liver function tests.