Importance of Molecular Genetic Examination for Diagnostics of Wilson
Disease
Procházková D.1, Konečná P.1, Vrábelová S.2, Kozák L.2, Dastych M.3, Hrstková H.1
1. dětská interní klinika, FN Brno1 přednostka prof. MUDr. H. Hrstková, CSc. Centrum molekulární biologie a genové terapie IHOK, FN Brno2 přednosta prof. MUDr. J. Vorlíček, CSc. Oddělení klinické biochemie, FN Brno3 primář doc. MUDr. M. Dastych, CSc. |
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Summary:
Wilson disease (WD) is an autosomal recessive disorder of copper (Cu) transport with a frequency
of 1:40,000 live birth. The disease is caused by a deficiency of copper-transporting ATPase –
ATP7B (13q14.3-q21.1). The disorder becomes manifest as a chronic liver disease and/or neurological
impairment due to accumulation of copper in several tissues, principally the liver and brain.
The most frequent manifestation of WD is between 8 and 20 years of age. The diagnosis involves
determination of serum ceruloplasmine and Cu, detection of Cu in 24-hour collection of urine,
carrying out a test with penicillamine, liver biopsy determining the Cu content in the hepatic dry
weight and DNA diagnosis, if available. Interpretation of biochemical findings changes due to
DNA analysis of mutations. As yet there is no exact correlation between the genotype and phenotype
of the patient. Therapy of the disease is developing and at the present time is accepted for
the hepatic from in childhood as a standard therapy with chelates and zinc. In the final stage the
solution would be liver transplantation.
The group included 22 children from 5 to 17 years of age. The 1st group (12) consisted of heterozygotes
for WD, siblings or offspring of patients with WD confirmed by DNA diagnosis. The 2nd
group (10) were patients with hepatic form of WD, confirmed by DNA diagnosis and assessment
of the copper content in hepatic dry weight. The control group consisted of 11 children aged 4 to
16 years.
In 4 probands of the 1st group, i.e. 33.3%, authors discovered that the level of ceruloplasmine
in blood had decreased below 0.2 g/l (ranging between 0.12 and 0.43 g/l). They proved a statistically
significant difference (P < 0.05) for CP in the serum among heterozygotes for WD; i.e. among
the offspring of mothers with WD and siblings of probands with WD. Threshold levels of copper
were determined in the basic collection of urine of 4 children (i.e. 0.6 μmol). The copper level in
the 24-hour urine collection of 11 heterozygotes in the test with penicillamine did not exceed
12.5 μmol.
In 7 children of the 2nd group authors demonstrated a serum level of ceruloplasmine lower than
0.2 g/l, i.e. 70% (between 0.03 and 0.22 g/l). All the 24-hour urine collections for copper contained
elevated residues of more than 0.6 μmol (between 0.8 and 2.67 μmol). Contrary to expectations
levels higher than 1.6 μmol were detected only in 4 children. A statistically significant difference
(P < 0.05) in the 24-hour excretion of copper into urine was discovered between the control group
of healthy children and probands with WD, also according to the sex of the investigated individuals.
In the test with penicillamine the Cu residue in urine was lower than 20 μmol (indicated as
an extreme level for WD) in 8 probands. Urinary copper excretion after penicillamine administration
do not contribute to the differentiation of heterozygotes and patients with WD.
An important way of screening is the determination of the copper content in hepatic dry
weight. However, authors assume that interpretation of these findings will change in the near
future in view of DNA diagnosis of mutations. According to these results examinations of the Kayser-
Fleischer ring in early childhood hepatic forms are not very important.
In a proband with the genotype IVS12+1G>A/G1355C they discovered that the heavier the form
of mutation demonstrated in a WD patient, the more severe the clinical course of the disease can
be expected.
Serious mutation in the heterozygotes may mimic WD. Authors recorded an attack of anxiety
disorder in a girl with the genotype H1069Q/W779X. In children with the allele H1069Q they
demonstrated minimal brain damage, graphomotoric inaptitude and slightly abnormal EEG in
the basic activity without a clinical correlate.
Key words:
Wilson disease, genotype, phenotype
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