20-year experience on prenatal diagnosis in a reference university medical genetics center in Turkey

Background/aim

Although cutting edge procedures such as cell-free fetal DNA isolation from maternal blood are now available, invasive prenatal tests are still being used extensively for prenatal diagnosis. The study aims to evaluate the demographic data, indications, and cytogenetic results of 9297 results of patients who underwent prenatal invasive testing for genetic analysis that were referred for the last 20 years in a University Medical Genetics Center.

Materials and methods

The records of 8363 amniocenteses, 626 chorionic villus, and 308 cordocenteses samples were retrospectively evaluated and analyzed regarding referral reasons, indications and their cytogenetic results. The total numbers and the percentages of each group were recorded; Chi-square and logistic regression analyses were performed to give the statistical likelihood of different events.

Results

The number of referrals decreased significantly after 2009. Risk of having trisomy 21 as well as trisomy 13 and 18 significantly increased in parallel with advanced maternal age. When the 21–25 age group was compared to the older age groups in terms of having a trisomy 21 pregnancy, the risk doubled in the 36–40, 5 times higher in 41–45 and 10-fold in 46–50 age groups. No significant linear correlation between maternal serum screening test results and trisomy 21 was found, however the difference between the pregnancies whom cut-off value above and below 1/250 in maternal serum screening test were significant.

Conclusion

These data have provided useful information on the frequency of referrals to the reference genetics department, and the feasibility of genetic services. By reviewing the indications and their corresponding results, we can offer invaluable insights that will be useful in genetic counseling and also in the development of more effective genetic strategies.

Clinical Contribution of Next-Generation Sequencing Multigene Panel Testing for BRCA Negative High-Risk Patients With Breast Cancer

BACKGROUND

Breast cancer is the most common malignancy in women and thought to be hereditary in 10% of patients. Recent next-generation sequencing studies have increased the detection of pathogenic or likely pathogenic (P/LP) variants in genes other than BRCA1/2 in patients with breast cancer. This study evaluated pathogenic variants, likely pathogenic variants, and variants of unknown significance in 18 hereditary cancer susceptibility genes in patients with BRCA1/2-negative breast cancer.

PATIENTS AND METHODS

This retrospective study included 188 high-risk BRCA1/2-negative patients with breast cancer tested with a multigene cancer panel using next-generation sequencing.

RESULTS

Among 188 proband cases, 18 variants in 21 patients (11.1%) were classified as P/LP in PALB2 (n = 6), CHEK2 (n = 5), MUTYH (n = 4), ATM (n = 3), TP53 (n = 2), BRIP1 (n = 1), and MSH2 (n = 1). Three novel P/LP variants were identified. An additional 28 variants were classified as variants of unknown significance and detected in 30 different patients (15.9%).

CONCLUSION

This is one of the largest study from Turkey to investigate the mutation spectrum in non-BRCA hereditary breast cancer susceptibility genes. A multigene panel test increased the likelihood of identifying a molecular diagnosis in patients with BRCA 1/2-negative breast cancer at risk for a hereditary breast cancer syndrome. More studies are needed to enable the clinical interpretation of these P/LP variants in hereditary patients with breast cancer.

A Neurofibromatosis Noonan Syndrome Patient Presenting with Abnormal External Genitalia

Neurofibromatosis Noonan syndrome (NFNS) is a rare RASopathy syndrome, resulting from NF1 gene mutations. NFNS is characterized by phenotypic features of both neurofibromatosis type 1 (NF1) and Noonan syndrome. Plexiform neurofibromas (PNFs) are an unusual finding in NFNS. A seven year-old girl with typical clinical features of NF1 was referred to our clinic due to short stature and abnormal genital appearance. Due to dysmorphic features, a clinical diagnosis of NFNS was considered in the patient and, following molecular analysis, revealed a novel heterozygous c.3052_3056delTTAGT (p.L1018X) variant in the NF1 gene. Although evaluation for genital virilization, including karyotype and hormonal studies were normal, imaging studies revealed a diffuse genital PNF. Although PNFs are seen rarely in NFNS, this should be considered in the differential diagnosis of genital virilization in these patients to prevent unnecessary testing.

Rapid Molecular Genetic Diagnosis with Next-Generation Sequencing in 46,XY Disorders of Sex Development Cases: Efficiency and Cost Assessment

BACKGROUND/AIM

The aim of this study was to use targeted next-generation sequencing (TNGS) including all known genes associated with 46,XY disorders of sex development (DSD) for a fast molecular genetic diagnosis.

METHODS

Twenty pediatric patients were recruited, and 56 genes related to 46,XY DSD were sequenced using TNGS. The time elapsed between initial appointment and final diagnosis as well as the mean expenditure was determined.

RESULTS

A total of 9 (45%) mutations in 4 different genes were identified. Mutations in the HSD17B3 gene were observed in 6 (30%) patients. A heterozygous mutation in WT1 gene and a hemizygous mutation in SRY gene were detected in patients with gonadal dysgenesis. One patient had a homozygous mutation in LHCGR gene. Prior to the molecular diagnosis, the mean number of clinical visits, time elapsed until diagnosis, and expenditure were 27.4 ± 14.6 visits, 5.9 ± 4.1 years per patient, and USD 2,142 ± 1,038, respectively. With TNGS, time elapsed until diagnosis was significantly reduced (3 days), and expenditure per patient was only one third of the conventional approach (USD 761).

CONCLUSIONS

TNGS is an efficient, rapid, and cost-effective technique for mutation detection in 46,XY DSD.

Von Hippel-Lindau Disease: The Importance of Retinal Hemangioblastomas in Diagnosis

Von Hippel-Lindau (VHL) disease is a familial cancer syndrome characterized by benign or malignant tumors which may involve more than one system. Retinal hemangioblastomas are usually the initial manifestation of VHL disease and can cause vision loss. A 32-year-old man presented to our clinic with vision loss in the left eye for 2 months. He had a history of cerebral hemangioblastoma operation. Family history showed that his mother had unilateral vision loss and died because of renal cell carcinoma. Ophthalmologic examination revealed multiple retinal hemangioblastomas in both eyes. VHL gene sequencing was performed and heterozygous p.R161X mutation was detected. His sister and daughter were also found to have the same variant. A treatment and follow-up plan was initiated for the patient and affected family members. Considering VHL disease in the differential diagnosis of retinal hemangioblastomas has a very important role in the early detection of life-threatening tumors in these patients.