Pathophysiology
Copper is needed by the body for a number of functions, predominantly as a cofactor for a number of enzymes such as ceruloplasmin, cytochrome c oxidase, dopamine β-hydroxylase, superoxide dismutase and tyrosinase.Copper enters the body through the digestive tract. A transporter protein on the cells of the small bowel, copper membrane transporter 1 (Ctr1; SLC31A1), carries copper inside the cells, where some is bound to metallothionein and part is carried by ATOX1 to an organelle known as the trans-Golgi network. Here, in response to rising concentrations of copper, an enzyme called ATP7A (Menkes protein) releases copper into the portal vein to the liver. Liver cells also carry the CMT1 protein, and metallothionein and ATOX1 bind it inside the cell, but here it is ATP7B that links copper to ceruloplasmin and releases it into the bloodstream, as well as removing excess copper by secreting it into bile. Both functions of ATP7B are impaired in Wilsons disease. Copper accumulates in the liver tissue; ceruloplasmin is still secreted, but in a form that lacks copper (termed apoceruloplasmin) and is rapidly degraded in the bloodstream.When the amount of copper in the liver overwhelms the proteins that normally bind it, it causes oxidative damage through a process known as Fenton chemistry; this damage eventually leads to chronic active hepatitis, fibrosis (deposition of connective tissue) and cirrhosis. The liver also releases copper into the bloodstream that is not bound to ceruloplasmin. This free copper precipitates throughout the body but particularly in the kidneys, eyes and brain.
High urine copper levels are not unique to Wilsons disease; they are sometimes observed in autoimmune hepatitis and in cholestasis (any disease obstructing the flow of bile from the liver to the small bowel).In children, the penicillamine test may be used. A 500 mg oral dose of penicillamine is administered, and urine collected for 24 hours. If this contains more than 1600 μg (25 μmol), it is a reliable indicator of Wilsons disease. This test has not been validated in adults. Liver biopsy
Once other investigations have indicated Wilsons disease, the ideal test is the removal of a small amount of liver tissue through a liver biopsy. This is assessed microscopically for the degree of steatosis and cirrhosis, and histochemistry and quantification of copper are used to measure the severity of the copper accumulation. A level of 250 μg of copper per gram of dried liver tissue confirms Wilsons disease. Occasionally, lower levels of copper are found; in that case, the combination of the biopsy findings with all other tests could still lead to a formal diagnosis of Wilsons.In the earlier stages of the disease, the biopsy typically shows steatosis (deposition of fatty material), increased glycogen in the nucleus, and areas of necrosis (cell death). In more advanced disease, the changes observed are quite similar to those seen in autoimmune hepatitis, such as infiltration by inflammatory cells, piecemeal necrosis and fibrosis (scar tissue). In advanced disease, finally, cirrhosis is the main finding.