Wilson's disease (hepatolenticular degeneration) is a heredity autosomal recessive metabolic disease with a frequency of 1:30000 caused by the deficit of the copper-transporting ATPase (ATP 7B) which leads to the failure of copper excretion into bile and failure of incorporation into apoceruloplasmin. The consequence is a cumulative retention of extensive quanta of copper chronically intoxicating many organs, mainly the brain and liver (hepatic and neurological form) that is the basic pathogenic mechanism leading to tissue damage and organ changes.
The ATP7B gene is located in the region 13q14.3q21.1, has 21 exons and its product is 7.5 kb in size. It is expressed mainly in hepatocytes, kidney and placenta and in lower extent in the brain, heart, muscles and pancreas. A genetic defect leads to the failure of copper transport from the trans-Golgi apparatus into lysosomes and thence into the bile and also the failure of copper transport for the synthesis of ceruloplasmin.
So far, there have been published more than 200 mutations of the ATP7B gene (missence and nonsence substitutions, small insertions, deletions and splicing mutations). The most common mutation in the Czech Republic is the substitution of histidine for glutamin in a position 1069 (p.H1069G) with a frequency of 57 %.
An important specificity of Wilson's desease is its curability (appropriate diet, penicilamine and zinc preparations) which, in the case of early diagnosis and treatment, is succesful enough to be able to stop the progression of the disease completely or to prevent the manifestation of gene defect.
Genetic examination is benefitial mainly for siblings in families with a demonstrated occurence of Wilson's disease and in the asymptomatic stage of the disease.
The most common form of liver manifestation is a liver cirrhosis with a tendency of having a quick progression. That is why all etiologically unclear liver cirrhosis in individuals younger than 45 years old should be examined for the possibility of WD.
In our laboratory, we perform the mutation analysis of all coding regions of the ATP7B gene including exon - intron joints using PCR and direct sequencing.
Germline mutations detected by sequence analysis of the coding exons and exon-intron connections of the gene ATP7B are detected in approximately 98% of patients meeting the diagnostic criteria for Wilson's disease.
MLPA (Multiple-Ligation Probe Amplification) analysis of the mutation in a large-scale (amplification / deletion) detects about 1% of mutations in the gene ATP7B listed in a publicly available version of the mutation database HGMD.
Analytical sensitivity and specificity of the sequencing: 99%.
Mutations deep in the introns and regulatory sequences are not detected. Rare polymorphisms in the location of primers annealing may cause a diagnostic error.