Road to A Rare Diagnosis: A Case Report Exploring Phenotype, Clinical Management and Outcome of a Rare and Novel Unbalanced Translocation causing complete Trisomy 17p

Background: Trisomy 17 is a rare chromosomal disorder with limited existing literature that mostly refer to mosaic Trisomy 17 cases. Our report summarizes the clinical course of a neonate with a Trisomy 17 karyotype der (14;17) (q10; p10), + 17 pat. Key words: Trisomy 17, Unbalanced translocation, Paternal origin

Der(1;7)(q10;p10) Presents with a Unique Genetic Profile and Frequent ETNK1 Mutations in Myeloid Neoplasms

Background Der(1;7)(q10;p10) (der(1;7) is an unbalanced translocation recurrently found in myeloid neoplasms, particularly in myelodysplastic syndromes (MDS) and related disorders. Caused by a recombination between two homologous alphoid sequencing D1Z7 and D7Z1 on chromosomes 1 and 7, respectively, it results in monosomy 7q and trisomy 1q, which is implicated in the pathogenesis of der(1;7)-positive myeloid neoplasms. Previous studies reported frequent co-occurrence of +8 and del(20q), as well as RUNX1 mutations, the genetic and clinical characteristics of this abnormality has not fully been elucidated. Methods In this study, we enrolled a total of 153 cases myeloid neoplasms positive for der(1;7) from Japanese and German cohorts, in which co-occurring genetic lesions were analyzed using whole exome and/or targeted-capture sequencing. An additional 3,223 MDS and related neoplasm cases were also analyzed using targeted-capture sequencing to identify der(1;7)-specific genomic features. Results Ethnicity was evaluated comparing the frequency of der(1;7) in 944 German MDS cases and 763 Japanese MDS cases. Der(1;7) cases were observed at a higher frequency in Japanese MDS cohort compared to German MDS cohort (73/763 cases versus 4/944 cases, p < 0.00001). Der(1;7) cases showed a strong male predominance (86.3%) (p<0.001). Of 153 myeloid neoplasm patients harboring der(1;7), 114 were diagnosed with MDS, 28 with AML, 5 with MDS-MPN and 1 with MPN. Targeted-capture sequencing revealed mutations in common myeloid drivers (n=61) in 96% of der(1;7) cases. The most frequently mutated gene was RUNX1 with 46%, followed by ETNK1 (24.5%) and EZH2 (24.5%). Of interest, ETNK1 mutation was identified as the most unique to der(1;7) when compared to myeloid neoplasm cases without der(1;7) (n=3,066) [odds ratio (OR)=15.06], followed by ETV6 (OR=9.35) and EZH2 (OR=6.52). To further examine the uniqueness of this mutation profile, the mutational profile of der(1;7) was compared to those myeloid neoplasm cases harboring amp(1q) (n=52) and monosomy 7 (n=105). Highly frequent ETV6 and ETNK1 mutations were highly unique to der(1;7) cases when compared to amp(1q) cases (OR=3.72, OR=2.57, respectively). BCOR and ETNK1 mutations were highly unique to der(1;7) cases when compared to monosomy 7 cases (OR=35.88, OR=4.29, respectively). Both amp(1q) and monosomy 7 cases showed a higher mutation rate in TP53 compared to der(1;7) cases (49.1% and 51%, respectively, vs 3.5 %) . From these mutational characteristics, ETNK1 was identified as being the most unique to der(1;7) when compared to amp(1q), monosomy 7 and other myeloid neoplasm cases. ETNK1-mutated der(1;7) cases were featured with eosinophilia (p < 0.0005), a lack of RAS pathway mutations and trisomy 8 when compared to ETNK1-wild type der(1;7) cases. Survival analysis was conducted to elucidate the difference in survival in der(1;7) cases (n=65) versus myeloid neoplasm cases (n=2066). Der(1;7)-harboring myeloid neoplasm cases had a median overall survival of 6.8 months (95% CI, 3.5 to 11.9) and non-der(1;7) harboring myeloid neoplasm cases were 11.8 months (95% CI, 10.5 to 12.6). Thus, der(1;7)-harboring myeloid neoplasm cases had poorer prognosis (p<0.001). Conclusion In conclusion, der(1;7) is an unbalanced translocation that occurs predominantly in males and is seen more frequently in Japanese than Caucasian populations. Der(1;7) cases present with a mutational profile that is distinct from other myeloid neoplasm cases such as those with amp(1q) and monosomy7/del(7q), showing frequency of ETNK1 mutations. Disclosures Nannya: Otsuka Pharmaceutical Co., Ltd.: Consultancy, Speakers Bureau; Astellas: Speakers Bureau. Kern: MLL Munich Leukemia Laboratory: Other: Part ownership. Haferlach: MLL Munich Leukemia Laboratory: Other: Part ownership. Atsuta: Astellas Pharma Inc.: Speakers Bureau; Mochida Pharmaceutical Co., Ltd.: Speakers Bureau; AbbVie GK: Speakers Bureau; Kyowa Kirin Co., Ltd: Honoraria; Meiji Seika Pharma Co, Ltd.: Honoraria. Handa: Ono: Honoraria; BMS: Honoraria; Janssen: Honoraria; Daiichi Sankyo: Research Funding; Celgene: Honoraria, Research Funding; Chugai: Research Funding; Kyowa Kirin: Research Funding; Takeda: Honoraria, Research Funding; Sanofi: Honoraria, Research Funding; Abbvie: Honoraria; MSD: Research Funding; Shionogi: Research Funding. Ohyashiki: Novartis Pharma: Other: chief clinical trial; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Haferlach: MLL Munich Leukemia Laboratory: Other: Part ownership. Ogawa: Otsuka Pharmaceutical Co., Ltd.: Research Funding; Eisai Co., Ltd.: Research Funding; Kan Research Laboratory, Inc.: Consultancy, Research Funding; Dainippon-Sumitomo Pharmaceutical, Inc.: Research Funding; ChordiaTherapeutics, Inc.: Consultancy, Research Funding; Ashahi Genomics: Current holder of individual stocks in a privately-held company.

Characterization of a Rare Mosaic Unbalanced Translocation of t(3;12) in a Patient With Neurodevelopmental Disorders

Background Unbalanced translocations may be de novo or inherited from one parent carrying the balanced form and are usually present in all cells. Mosaic unbalanced translocations are extremely rare with a highly variable phenotype depending on the tissue distribution and level of mosaicism. Mosaicism for structural chromosomal abnormalities is clinically challenging for diagnosis and counseling due to the limitation of technical platforms and complex mechanisms, respectively. Here we report a case with a tremendously rare maternally-derived mosaic unbalanced translocation of t(3;12), and we illustrate the unreported complicated mechanism using single nucleotide polymorphism (SNP) array, fluorescence in situ hybridization (FISH), and chromosome analyses. Case Presentation: An 18-year-old female with a history of microcephaly, pervasive developmental disorder, intellectual disability, sensory integration disorder, gastroparesis, and hypotonia presented to our genetics clinic. She had negative karyotype by parental report but no other genetic testing performed previously. SNP microarray analysis revealed a complex genotype including 8.4 Mb terminal mosaic duplication on chromosome 3 (3p26.3->3p26.1) with the distal 5.7 Mb involving two parental haplotypes and the proximal 2.7 Mb involving three parental haplotypes, and a 6.1 Mb terminal mosaic deletion on chromosome 12 (12p13.33->12p13.31) with no evidence for a second haplotype. Adjacent to the mosaic deletion is an interstitial mosaic copy-neutral region of homozygosity (1.9 Mb, 12p13.31). The mother of this individual was confirmed by chromosome analysis and FISH that she carries a balanced translocation, t(3;12)(p26.1;p13.31). Conclusion Taken together, the proband, when at the stage of a zygote, likely carried the derivative chromosome 12 from this translocation, and a postzygotic mitotic recombination event occurred between the normal paternal chromosome 12 and maternal derivative chromosome 12 to “correct” the partial 3p trisomy and partial deletion of 12p. To the best of our knowledge, it is the first time that a mechanism utilizing a combined cytogenetic and cytogenomic approach, and we believe it expands our knowledge of mosaic structural chromosomal disorders and provides new insight into clinical management and genetic counseling.

SENSV: Detecting Structural Variations with Precise Breakpoints using Low-Depth WGS Data from a Single Oxford Nanopore MinION Flowcell

Structural variation (SV) is a major cause of genetic disorders. In this paper, we show that low-depth (specifically, 4x) whole-genome sequencing using a single Oxford Nanopore MinION flow cell suffices to support sensitive detection of SV, in particular, pathogenic SV for supporting clinical diagnosis. Existing SV calling software, when using 4x ONT WGS data, often fails to detect pathogenic SV especially in the form of long deletion, terminal deletion, duplication, and unbalanced translocation. Our new SV calling software SENSV is able to achieve high sensitivity for all types of SV and a breakpoint precision typically ±100 bp, both features are important for clinical concerns. The improvement achieved by SENSV stems from several new algorithms. We evaluated SENSV and other software using both real and simulated data. The former was based on 24 patient samples, each diagnosed with a genetic disorder. SENSV found the pathogenic SV in 22 out of 24 cases (all heterozygous, size from hundreds of Kbp to a few Mbp), reporting breakpoints within 100 bp of the true answers. No existing software can detect the pathogenic SV in more than 10 out of 24 cases, even when the breakpoint requirement is relaxed to ±2,000 bp.

Severe hypercalcemia in an infant with unbalanced translocation of chromosomes 2 and 8: a possible contribution of 2p duplication

Objectives We report an uncommon case of severe hypercalcemia in an infant with unbalanced translocation of chromosomes 2 and 8 with 2p duplication. After ruling out all the possible etiologies of hypercalcemia, we speculated a potential contribution of 2p duplication involving 225 genes. Case presentation An 11-month old female infant with global developmental delay, failure to thrive (FTT), hypotonia, amblyopia, constipation, and recent onset emesis was admitted to the hospital after an incidental diagnosis of severe hypercalcemia. Labs revealed normal serum phosphate, serum 25 (OH) vitamin D levels, and low serum parathyroid hormone (PTH) level. Elevated urinary calcium to creatinine ratio ruled out the possibility of hypocalciuric hypercalcemia. Endocrinological evaluations, including thyroid function test, Adrenocorticotropic hormone (ACTH), Cortisol, Insulin like growth factor 1 (IGF-1) were all normal. Transient elevation of parathyroid hormone related peptide (PTHrP) level was noted, but skeletal survey, chest X-ray and lab values including low 1,25 (OH)2 cholecalciferol, lactate dehydrogenase (LDH), uric acid (UA), erythrocyte sedimentation rate (ESR) excluded granulomatous diseases and malignancies. Further evaluation with chromosomal microarray (CMA) and whole exome gene sequencing (WES) showed an unbalanced chromosomal translocation with 2p duplication involving 225 genes. The infant showed an improvement with medical management. Conclusions 2p duplication syndrome is a rare syndrome characterized by developmental delay, feeding problems, FTT, hypotonia, constipation, and unusual facial features as noted in our case. However, hypercalcemia has been only reported once earlier in 2p duplication syndrome, which was the presenting feature of our case. We attributed this genetic syndrome as an underlying etiology for hypercalcemia after ruling out all the common potential causes of hypercalcemia.