[Birt-Hogg-Dubé syndrome]. / Syndrom Birt-Hogg-Dubé

Birt-Hogg-Dubé syndrome (BHDS, MIM 135150) is an autosomal dominant condition characterized by presence of skin fibrofolliculomas, lung cysts, spontaneous pneumothorax and renal cancer. The disease is caused by germ-line mutations of the FLCN gene, which encodes protein folliculin. BHDS is a rare condition with high penetrance and variable expression. Clinical recommendations include increased care during general anesthesia due to a higher risk of pneumothorax, and long-term follow-up due to an elevated risk of renal cancer. Diagnostic and predictive DNA tests are available; prenatal and preimplantation diagnosis is possible.

[Juvenile polyposis syndrome]. / Juvenilný polypózny syndróm.

Juvenile polyposis syndrome (JPS) is an autosomal dominant disorder characterized by the occurrence of juvenile polyps and predisposition to cancer of the gastrointestinal tract (GIT). Characteristic feature of juvenile polyps are irregular cystic glands filled with mucus not observed in other colorectal cancer syndromes. Germline mutations in the SMAD4 and BMPR1A genes are found in 40% of the JP individuals. Hereditary hemorrhagic telangiectasia (HHT) and higher frequency of gastric polyposis are associated mostly with SMAD4 mutations.

[Rhabdoid tumours]. / Rhabdoidné nádory.

Rhabdoid tumors (RT) are rare highly malignant tumors. They are part of the embryonic types of tumors and therefore occur in early childhood (between ages of 0-2 years). The most common locations are brain and kidney, but RTs arising usually from soft tissues have been reported widely at most anatomical sites in the body. These tumors are composed of rhabdoid cells alone or as a mixture with primitive neuroectodermal cells, mesenchymal cells and/or epithelial cells, commonly denoted as atypical teratoid/rhabdoid tumours (AT/RT). Based on extremely rare incidence and usually non-specific histological picture, molecular genetic studies are extremely helpful in confirming diagnosis of RT. Biallelic inactivation mutation of the SMARCB1 gene plays a crucial role in the pathogenesis of most RT. One third of mutations are germline mutations leading to the designation of the so-called rhabdoid predisposition syndrome. Molecular genetic analysis of the SMARCB1 gene might be beneficial in the establishment of correct diagnosis, genetic counselling and for epidemiologic studies.

[Hereditary diffuse gastric cancer]. / Hereditární difuzní karcinom zaludku.

Hereditary diffuse gastric cancer is an autosomal dominant syndrome with a high lifetime risk of diffuse gastric cancer and also a high risk of lobular breast carcinoma. Hereditary diffuse gastric cancer (HDGC) is characterized by late presentation and a poor prognosis. The average age of onset of HDGC is 38 years, with a range of 14-69 years. The estimated lifetime risk of developing gastric cancer by age 80 is 67% for men and 83% for women. Many families with HDGC have germline mutations in the E-cadherin (CDH1) gene. We describe indication for genetic testing of germline mutations in CDH1 gene, possibilities of predictive testing, preventive care, prophylactic gastrectomy and preimplantation diagnosis.

Unique mutational profile associated with a loss of TDG expression in the rectal cancer of a patient with a constitutional PMS2 deficiency.

Cells with DNA repair defects have increased genomic instability and are more likely to acquire secondary mutations that bring about cellular transformation. We describe the frequency and spectrum of somatic mutations involving several tumor suppressor genes in the rectal carcinoma of a 13-year-old girl harboring biallelic, germline mutations in the DNA mismatch repair gene PMS2. Apart from microsatellite instability, the tumor DNA contained a number of C:G→T:A or G:C→A:T transitions in CpG dinucleotides, which often result through spontaneous deamination of cytosine or 5-methylcytosine. Four DNA glycosylases, UNG2, SMUG1, MBD4 and TDG, are involved in the repair of these deamination events. We identified a heterozygous missense mutation in TDG, which was associated with TDG protein loss in the tumor. The CpGs mutated in this patient's tumor are generally methylated in normal colonic mucosa. Thus, it is highly likely that loss of TDG contributed to the supermutator phenotype and that most of the point mutations were caused by deamination of 5-methylcytosine to thymine, which remained uncorrected owing to the TDG deficiency. This case provides the first in vivo evidence of the key role of TDG in protecting the human genome against the deleterious effects of 5-methylcytosine deamination.

[Our experience with analysis of the PTEN gene in patients suspected of having Cowden syndrome]. / Nase skúsenosti s analýzou génu PTEN u pacientov s podozrenim na Cowdenovej syndróm.

BACKGROUNDS: Cowden syndrome (CS) is a rare autosomal dominant disorder with an increased risk of breast, thyroid and uterine cancer development. The International Cowden Consortium has defined strict diagnostic criteria for individuals and families suspected of having CS. PATIENTS AND METHODS: We analyzed the genomic DNA of 16 patients by sequencing analysis and MLPA (multiplex ligation-dependent probe amplification) method. RESULTS: We found germline mutations, c.825_840del, resp. c.438delT, in 2 patients. Both patients fulfilled strict diagnostic criteria. The other patients, except one, who did not fulfil the criteria, did not harbour any pathogenic mutation. Patients not fulfilling strict diagnostic criteria were included in the study according to major CS criteria but not pathogenic. CONCLUSION: Our results and information from relevant articles show that strict international criteria are well established and analysis of "CS-like" patients has no significant prognostic meaning.