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Wilson disease is an autosomal recessive disorder of copper metabolism. The gene defective in Wilson disease encodes a copper transporting P-type ATPase expressed in the liver. The disturbed export of copper into bile results in accumulation of copper in liver and secondarily in other organs such as the brain. These patients generally present with either hepatic or neurological symptoms.

Pyruvate kinase (PK) deficiency is a common cause of hereditary non-spherocytic haemolytic anaemia. It is an autosomal recessive disorder caused by mutations in the gene coding for erythrocyte and liver-type pyruvate kinase (PKLR). So far, more than 130 mutations in this gene have been identified. Clinical symptoms, usually restricted to homozygous and compound-heterozygous individuals, are variable, ranging from neonatal jaundice requiring erythrocyte transfusions to a fully compensated haemolytic anaemia. The exact mechanism of erythrocyte destruction is unknown, however adenosine-triphosphate depletion and an increase in 2,3-disphosphoglycerate are thought to be important. The diagnosis of pyruvate kinase deficiency depends upon the demonstration of low PK enzyme activity. Due to the pitfalls in determining true PK activity, DNA testing is a valuable tool in the diagnosis of pyruvate kinase deficiency. By centralizing the molecular diagnostics of pyruvate kinase deficiency in Utrecht, more care can be provided for the diagnosis, treatment and support of patients.

Within a few years the 80,000 human genes will be identified which will increase our understanding of the genetic aspects of a large number of diseases, not only the relatively rare monogenic diseases but also the more frequent multifactorial diseases such as atherosclerosis, thrombosis and schizophrenia. Pharmacogenomics will lead to particular medication that is tuned to the genetic variations of the patient. Presently this increase in knowledge in the area of DNA diagnosis and genetic counselling will lead to a continuous increase in requests for assays. The possibilities for application will depend on new technological developments such as the DNA array technology and automation. To meet the increasing number of requests for genetic counselling, genetic nurses will have to play an important role. Moreover, collaboration between clinical geneticists and other specialists will have to be further intensified.