[The role of the pathologist in the diagnosis and monitoring of Wilson's disease].

Wilson's disease (WD) is an inherited disorder of copper metabolism, characterized by copper accumulation in different organs. The clinical presentation of WD is variable: juvenile cirrhosis, with or without neurological symptoms, fulminant hepatitis, acute intravascular hemolysis or late onset with neurological or psychiatric symptoms. The histological picture, the histochemical stains and the ultrastructural findings of the liver are variable in WD. The recent cloning of the WD gene and the report of several mutations (at least 25) of the WD gene suggest the hypothesis that the clinical and pathological variability of this disease is related to a genetic polymorphism. These data may explain why the diagnosis of WD is often extremely difficult for the pathologist, since histochemical stains for copper may be highly variable or negative, despite increased levels of tissue copper concentrations. The most important pathological data are: 1) the evaluation of liver architecture, relevant in the staging of liver disease in three stages; 2) histochemistry for copper, which is variable and needs the use of multiple methods: Timm's method is probably the most useful one, since it shows copper deposits even in the first stage of WD, when liver changes are often reversible; 3) the determination of copper concentration may be crucial in WD diagnosis; copper levels exceeding 250 ug/g of dry tissue are considered diagnostic for the disease; 4) transmission electron microscopy shows, mainly in youngsters, mitochondrial changes considered typical of WD; the ultrastructural picture may be diagnostic for WD in cases with not specific histology and negative histochemical stains; 5) scanning electron microscopy after osmic maceration may be a new useful tool in the study of this liver disease: this technique may give both panoramic and high-power enlargements and allows the localization in the acinar zones of the intracellular hepatocytic changes. Finally, only the optimal approach to liver biopsy, obtaining the highest number of histological, histochemical, quantitative and ultrastructural data, may allow the pathologist to an early diagnosis of WD.