Rachel Susman

Phenotypic expansion and further characterisation of the 17q21.31 microdeletion syndrome

Background: The recognition of the 17q21.31 microdeletion syndrome has been facilitated by high resolution microarray technology. Recent clinical delineation of this condition emphasises a typical facial appearance, cardiac and renal defects, and speech delay in addition to intellectual disability, hypotonia and seizures. Methods and results: We describe 11 previously unreported patients expanding the phenotypic spectrum to include aortic root dilatation, recurrent joint subluxation, conductive hearing loss due to chronic otitis media, dental anomalies, and persistence of fetal fingertip pads. Molecular analysis of the deletions demonstrates a critical region spanning 440 kb involving either partially or wholly five genes, CRHR1, IMP5, MAPT, STH, and KIAA1267. Conclusion: These data have significant implications for the clinical diagnosis and management of other individuals with 17q21.31 deletions.

Novel SOX2 partner-factor domain mutation in a four-generation family

Anophthalmia (no eye), microphthalmia (small eye) and associated ocular developmental anomalies cause significant visual handicap. In most cases the underlying genetic cause is unknown, but mutations in some genes, such as SOX2, cause ocular developmental defects, particularly anophthalmia, in a subset of patients. Here, we describe a four-generation family with a p.Asp123Gly mutation in the highly conserved partner-factor interaction region of the SOX2 protein, which is important for cell-specific actions of SOX2. The proband in this family has bilateral anophthalmia and several other family members have milder ocular phenotypes, including typical optic fissure coloboma. Expression studies indicate that Sox2 is expressed in the eye at the site of closure of the optic fissure during development. The SOX2 mutation in this family implicates the partner-factor interaction region of SOX2 in contributing to the specificity of SOX2 action in optic fissure closure. Our findings indicate that investigation of SOX2 in a broad range of eye anomaly patients aids in the determination of particular functions of SOX2 in development.

Prenatal and postnatal presentation of severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN) due to the FGFR3 Lys650Met mutation.

We present prenatal and postnatal features of a patient with severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN). Mutation analysis confirmed the clinical diagnosis by detecting the FGFR3 Lys650Met mutation. This case, one of only six with molecular analysis reported in the literature, confirms the severe morbidity and adds to the reports with early mortality associated with SADDAN. Clinical–radiological characteristics of all reported cases of SADDAN are reviewed and discussed.

Demonstration of a novel Xp22.2 microdeletion as the cause of familial extreme skewing of X-inactivation utilizing case-parent trio SNP microarray analysis

We report a kindred referred for molecular investigation of severe hemophilia A in a young female in which extremely skewed X‐inactivation was observed in both the proband and her clinically normal mother.

Bayesian approach to determining penetrance of pathogenic SDH variants

Background Until recently, determining penetrance required large observational cohort studies. Data from the Exome Aggregate Consortium (ExAC) allows a Bayesian approach to calculate penetrance, in that population frequencies of pathogenic germline variants should be inversely proportional to their penetrance for disease. We tested this hypothesis using data from two cohorts for succinate dehydrogenase subunits A, B and C (SDHA–C) genetic variants associated with hereditary pheochromocytoma/paraganglioma (PC/PGL). Methods Two cohorts were 575 unrelated Australian subjects and 1240 unrelated UK subjects, respectively, with PC/PGL in whom genetic testing had been performed. Penetrance of pathogenic SDHA–C variants was calculated by comparing allelic frequencies in cases versus controls from ExAC (removing those variants contributed by The Cancer Genome Atlas). Results Pathogenic SDHA–C variants were identified in 106 subjects (18.4%) in cohort 1 and 317 subjects (25.6%) in cohort 2. Of 94 different pathogenic variants from both cohorts (seven in SDHA, 75 in SDHB and 12 in SDHC), 13 are reported in ExAC (two in SDHA, nine in SDHB and two in SDHC) accounting for 21% of subjects with SDHA–C variants. Combining data from both cohorts, estimated lifetime disease penetrance was 22.0% (95% CI 15.2% to 30.9%) for SDHB variants, 8.3% (95% CI 3.5% to 18.5%) for SDHC variants and 1.7% (95% CI 0.8% to 3.8%) for SDHA variants. Conclusion Pathogenic variants in SDHB are more penetrant than those in SDHC and SDHA. Our findings have important implications for counselling and surveillance of subjects carrying these pathogenic variants.

Psychological outcomes and surgical decisions after genetic testing in women newly diagnosed with breast cancer with and without a family history

In patients with early breast cancer, personal and tumour characteristics other than family history are increasingly used to prompt genetic testing to guide women’s cancer management (treatment-focused genetic testing, ‘TFGT’). Women without a known strong family history of breast and/or ovarian may be more vulnerable to psychological sequelae arising from TFGT. We compared the impact of TFGT in women with (FH+) and without (FH−) a strong family history on psychological adjustment and surgical decisions. Women aged <50 years with high-risk features were offered TFGT before definitive breast cancer surgery and completed self-report questionnaires at four time points over 12 months. All 128 women opted for TFGT. TFGT identified 18 carriers of a disease-causing variant (50.0% FH+) and 110 non-carriers (59.1% FH+). There were no differences based on family history in bilateral mastectomy (BM) uptake, p = .190, or uptake of risk-reducing bilateral salpingo-oophorectomy (RRBSO), p = .093. FH− women had lower decreases in anxiety a year after diagnosis, p = .011, and regret regarding their decision whether to undergo BM, p = .022, or RRBSO, p = .016 than FH + women. FH− carriers reported significantly higher regret regarding their TFGT choice (p = .024) and test-related distress (p = .012) than FH + carriers, but this regret/distress could not be attributed to a concern regarding a possible worse prognosis. These findings indicate that FH− women may require additional counselling to facilitate informed decisions. Carriers without a family history may require additional follow-up counselling to facilitate psychological adjustment to their positive variant results, extra support in making surgical decisions, and counselling about how best to communicate results to family members.

The association between multiple pilomatrixomas and APC gene mutations

Dear Editor, Familial adenomatous polyposis is an autosomal dominant disorder caused by a germline mutation of the tumour suppressor gene adenomatous polyposis coli (APC) located on chromosome 5q22.2. Familial adenomatous polyposis is characterized by the development of hundreds of polyps in the colorectum, typically beginning in the second or third decade of life and eventually progressing to colorectal cancer in nearly all individuals if left untreated.