ABSTRACT
The cancer risk is unknown for those families in which a microsatellite instable tumour is neither explained by MLH1 promoter methylation nor by a germline mutation in a mismatch repair (MMR) gene. Such information is essential for genetic counselling. Families suspected of Lynch syndrome (n = 614) were analysed for microsatellite instability, MLH1 promoter methylation and/or germline mutations in MLH1, MSH2, MSH6, and PMS2. Characteristics of the 76 families with a germline mutation (24 MLH1, 2 PMS2, 32 MSH2, and 18 MSH6) were compared with those of 18 families with an unexplained microsatellite instable tumour. The mean age at diagnosis of the index patients in both groups was comparable at 44 years. Immunohistochemistry confirmed the loss of an MMR protein. Together this suggests germline inactivation of a known gene. The Amsterdam II criteria were fulfilled in 50/75 families (66%) that carried a germline mutation in an MMR gene and in only 2/18 families (11%) with an unexplained microsatellite instable tumour (P<0.0001). Current diagnostic strategies can detect almost all highly penetrant MMR gene mutations. Patients with an as yet unexplained microsatellite instable tumour likely carry a different type of mutation that confers a lower risk of cancer for relatives.
Subject(s)
Carcinoma/genetics , Colorectal Neoplasms, Hereditary Nonpolyposis/genetics , Colorectal Neoplasms/genetics , Genetic Predisposition to Disease , Microsatellite Instability , Adaptor Proteins, Signal Transducing/genetics , Adult , Aged , Algorithms , DNA Methylation , DNA Mismatch Repair , DNA-Binding Proteins/genetics , Family , Germ-Line Mutation , Humans , Middle Aged , MutL Protein Homolog 1 , MutS Homolog 2 Protein/genetics , Nuclear Proteins/genetics , Promoter Regions, Genetic , Risk FactorsABSTRACT
In three patients, two males aged four months and 39 years, and a female aged 19 years, trisomy 9p (the threefold presence of the short arm of chromosome 9) was diagnosed. The main symptoms are mental retardation, brachycephaly, hypertelorism with deep-set eyes, broad base of the nose, short philtrum, carp-shaped mouth, cup-shaped ears, short fingers and clinodactyly. Trisomy 9p is often caused by a balanced translocation in one of the parents. Therefore, cytogenetic studies of the parents and if appropriate other relatives are necessary. If one of the parents carries a translocation, the recurrence risk may vary from 2% to 15%. This depends on the length and origin of the chromosomal translocation segments. In case a translocation is found, genetic counselling of family members is warranted; it should include information concerning clinical symptoms, recurrence risks, prenatal diagnosis and other family planning alternatives.
Subject(s)
Chromosome Aberrations/diagnosis , Chromosome Aberrations/genetics , Chromosomes, Human, Pair 9/genetics , Syndrome , Trisomy/diagnosis , Adult , Chromosome Disorders , Family , Female , Genetic Counseling , Genetic Testing , Humans , Infant , Intellectual Disability/etiology , Male , Trisomy/geneticsABSTRACT
For families with a small number of cases of breast and/or ovarian cancer, limited data are available to predict the likelihood of genetic predisposition due to mutations in BRCA1 or BRCA2. In 104 families with three or more affected individuals (average 3.8) seeking counselling at family cancer clinics, mutation analysis was performed in the open reading frame of BRCA1 and BRCA2 by the protein truncation test and mutation-specific assays. In 31 of the 104 families tested, mutations were detected (30%). The majority of these mutations (25) occurred in BRCA1. Mutations were detected in 15 out of 25 families (60%) with both breast and ovarian cancer and in 16 out of 79 families (20%) with exclusively cases of breast cancer. Thus, an ovarian cancer case strongly predicted finding a mutation (P < 0.001). Within the group of small breast-cancer-only families, a bilateral breast cancer case or a unilateral breast cancer case diagnosed before age 40 independently predicted finding a BRCA1 or BRCA2 mutation (P = 0.005 and P = 0.02, respectively). Therefore, even small breast/ovarian cancer families with at least one case of ovarian cancer, bilateral breast cancer, or a case of breast cancer diagnosed before age 40, should be referred for mutation screening.
Subject(s)
Breast Neoplasms/genetics , Germ-Line Mutation , Neoplasm Proteins/genetics , Ovarian Neoplasms/genetics , Transcription Factors/genetics , Adult , BRCA2 Protein , Breast Neoplasms/pathology , DNA Mutational Analysis , Family , Female , Genes, BRCA1 , Genetic Markers/genetics , Genetic Predisposition to Disease , Humans , Middle AgedABSTRACT
Cytogenetic analysis was performed on peripheral blood lymphocytes of members of a family with inherited renal cell cancer. Four family members in three generations developed multiple/bilateral renal cell carcinomas of the clear cell type. In one additional case a bladder carcinoma was diagnosed. In two of the renal cell carcinoma patients a constitutional t(2;3)(q35;q21) was encountered, whereas in the two other (deceased) patients the presence of this translocation could be deduced. Also, the bladder cancer patient was found to be positive for t(2;3)(q35;q21). This is the third familial renal cell carcinoma-associated chromosomal translocation ever described. The previously reported cases also involved chromosome 3, thereby supporting the notion that this chromosome may play a crucial role in the development of renal cell carcinomas. Interestingly, the translocation breakpoints in these three families map at different locations, suggesting that multiple genes on chromosome 3 may be involved.
