Citations

Introduction: Short telomere syndromes (STS) are accelerated aging syndromes affecting hematopoietic, pulmonary, hepatobiliary and/or immunological systems. Clinical assessment of age-appropriate telomere length (TL) is performed using flow cytometry & fluorescence in-situ hybridization (flowFISH). Screening for germline variants in STS-related genes is guided by flowFISH-determined centile categories of TL, with screening recommended for TL <1st centile or 1-10th centile in lymphocytes (L) or granulocytes (G). However, the utility of genetic testing for patients with TL >10th centile and integration of clinical phenotype with flowFISH data in predictive algorithms is currently unclear. Methods: FlowFISH testing was done at reference laboratories in Vancouver (Repeat Diagnostics; Canada) & Johns Hopkins University (JHU, USA). Salient clinical features were pre-determined as, personal history of premature hair greying (onset at age < 30 years), idiopathic pulmonary fibrosis (IPF) or IPF/emphysema overlap (in smokers), cryptogenic cirrhosis or NRH, unexplained cytopenias &/or immunodeficiency, & family history of the above (in >1 1st or 2nd degree relatives). Clinical likelihood score (CLS) was assigned as low (1), intermediate (int, 2) or high (>2), based on the number of aforementioned clinical features present prior to flowFISH testing. Genetic testing was performed using either an in-house or commercial bone marrow failure-specific next generation sequencing (NGS) panel or whole exome sequencing (WES), and data for known variants affecting telomerase or telomeric function (TERT, TERC, DKC1, TINF2, NHP2, NOP10, TCAB1, NAF1, & RTEL1) was recorded. Results: One hundred forty-nine patients at our institution underwent TL assessment at Repeat diagnostics (n=38) and JHU (n=111) laboratories, respectively. Median age was 56 (range: 7-79) years; 88 (59%) being males. Significant family history was present in 40 (27%) patients, while premature greying of hair was present in 13 (9%) patients. Organ-specific clinical features included unexplained cytopenias (n=89, 60%) IPF (n=71, 48%), cryptogenic cirrhosis or NRH (n=21, 14%), & unexplained immunodeficiency (n=14, 9%). CLS stratification included low (n=74, 50%), int (n=54, 36%), & high (n=21, 14%), with higher CLS significantly correlating with lower delta TL for L (p=0.0005) but not G (p=0.3). Genetic testing was performed in 51 (35%) patients (NGS-51, WES-1) among which 13 (26%) patients had a telomere-associated variant; 5 (10%) pathogenic (pv, all TERT). CLS alone was unable to predict likelihood of finding a telomere-associated variant (p=0.4). Based on age-appropriate centile categorization of L & G TL (information for both available in 134 patients), patients were stratified into six groups (table 1). TL <1st centile in L: This group was further divided into two groups; TL<1st centile in both L & G [A1, n=7, CLS low-3 (43%), int-2 (29%), & high-2 (29%)] and TL <1st centile in L and 1-50th centile in G (A2, n=2, CLS low & high) patients. Among the 4 (57%) patients who underwent genetic (NGS-3, WES-1) testing, 3 (75%) had TERTpv in A1 subgroup and 1 A2 subgroup patient had a VUS in TERT.TL <1st centile in G, 1-10th centile in L (n=18): This group included 9 (50%) low, 8 (44%) int and 1 (6) high CLS patients, of which only 1 of 8 NGS-tested patients had TERTpv.TL 1-10th centile in L or G: This group was divided into; 1-10th centile in both L & G [C1, n=28, CLS low-3 (11%), int-14 (50%), high-11(39%)] of whom 8 (22%) underwent NGS with no pathogenic variants but 3 VUS in RTEL1, NAF1 & PARN genes, and 1-10th centile in L, >1-90th centile in G [C2, n=36, CLS low-19 (53%), 16 (44%), 1 (3%)] of whom 8 (22%) underwent NGS with 1 TERTpv and 2 VUS in TINF2TL >10th centile in L & 1-90th centile in G (n=43, 32%): CLS stratification in this group included 27 (63%) low, 12 (28%) int, 4 (9%) high. NGS testing was done in 13 (30%) patients [CLS low-9(69%), int 2(15%), high 2 (15%)], of whom only 2 (15%) had VUS in TINF2 and TERT gene, but no pathogenic variants (figure 1). Conclusion: Our study demonstrates the importance of using a flowFISH assay based predictive algorithm to screen patients with suspected STS for telomere-related genetic alternations, in comparison to a clinical likelihood score. We also demonstrate a limited role for genetic testing in patients with lymphocyte TL >10th centile, regardless of the clinical likelihood score. Disclosures Patnaik: Stem Line Pharmaceuticals.: Membership on an entity's Board of Directors or advisory committees.

AbstractBackgroundWe describe a patient presenting with pachygyria, epilepsy, developmental delay, short stature, failure to thrive, facial dysmorphisms, and multiple osteochondromas.MethodsThe patient underwent extensive genetic testing and analysis in an attempt to diagnose the cause of his condition. Clinical testing included metaphase karyotyping, array comparative genomic hybridization, direct sequencing and multiplex ligation‐dependent probe amplification and trio‐based exome sequencing. Subsequently, research‐based whole transcriptome sequencing was conducted to determine whether it might shed light on the undiagnosed phenotype.ResultsClinical exome sequencing of patient and parent samples revealed a maternally inherited splice‐site variant in the doublecortin (DCX) gene that was classified as likely pathogenic and diagnostic of the patient's neurological phenotype. Clinical array comparative genome hybridization analysis revealed a 16p13.3 deletion that could not be linked to the patient phenotype based on affected genes. Further clinical testing to determine the cause of the patient's multiple osteochondromas was unrevealing despite extensive profiling of the most likely causative genes, EXT1 and EXT2, including mutation screening by direct sequence analysis and multiplex ligation‐dependent probe amplification. Whole transcriptome sequencing identified a SAMD12‐EXT1 fusion transcript that could have resulted from a chromosomal deletion, leading to the loss of EXT1 function. Re‐review of the clinical array comparative genomic hybridization results indicated a possible unreported mosaic deletion affecting the SAMD12 and EXT1 genes that corresponded precisely to the introns predicted to be affected by a fusion‐causing deletion. The existence of the mosaic deletion was subsequently confirmed clinically by an increased density copy number array and orthogonal methodologiesConclusionsWhile mosaic mutations and deletions of EXT1 and EXT2 have been reported in the context of multiple osteochondromas, to our knowledge, this is the first time that transcriptomics technologies have been used to diagnose a patient via fusion transcript analysis in the congenital disease setting.

Mucopolysaccharidosis type VI (MPS VI) is a clinically heterogeneous lysosomal disease, which can be divided into 2 main categories on the basis of age of onset and severity of symptoms. The diagnosis of the attenuated form is often delayed given subtle facial features rather than the typical coarse facial features of the classic form. Here, we discuss the difficulties in establishing the diagnosis of MPS VI on the basis of the report of 4 individuals. The most common signs and symptoms in our series were bone abnormalities and hip pain as initial manifestations and cardiac changes detected after follow-up studies. On the basis of our cohort and others worldwide, awareness of attenuated forms of MPS VI should be increased particularly among general practitioners, pediatricians, rheumatologists, orthopedists, ophthalmologists, and cardiologists. Moreover, these health care providers should be aware of the technical aspects involved in the molecular and biochemical diagnosis process so that they are aware how diagnostic errors may occur.

ACTB encodes the β-actin, and pathogenic variations in this gene have typically been associated with Baraitser-Winter cerebrofrontofacial syndrome, a congenital malformation syndrome characterized by short stature, craniofacial anomalies, and cerebral anomalies. Here, we describe the third case with the p.Arg183Trp variant in ACTB causing juvenile-onset dystonia. Our patient has severe, intractable dystonia, developmental delay, and sensorineural hearing loss, besides hyperintensities in the caudate nuclei and putamen on the brain MRI, which is a distinct but overlapping phenotype with the previously reported case of identical twins with the same alteration in ACTB.