Trends in preimplantation genetic testing for monogenic disorders (pgt-m).

With increased availability of genetic testing, particularly expanded carrier screening (ECS) and hereditary cancer (HC) testing, the scope of conditions for which PGT-M is performed is expanding. Our aim was to report on indications for PGT-M from the past decade in our large academic practice. All PGT-M cases occurring between January 2010 and April 2021 were reviewed. A total of 331 patients were identified for which PGT-M was performed for 124 different genes over 582 cycles. Eighteen patients tested for two genes and one patient tested for three genes; therefore, there were a total of 351 unique PGT-M cases. Of the 124 genes tested, 82 (66.1%) were of childhood onset while 16 (12.9%) were of adult onset, and the remaining 26 (21.0%) were of variable onset. Over the entire study period, 70/351 patients (19.9%) tested for 16 genes related to HC syndromes; between 2010-2017, HC-related PGT-M accounted for 12.6% (20/159) of our total PGT-M volume, and since 2018, it rose to 26.0% (50/192). Overall, BRCA1 was the most common gene tested in our practice, and hereditary breast and ovarian cancer syndrome (BRCA1 and BRCA2) accounted for 15.1% (53/351) of our total PGT-M patient population. 181/351 patients (51.6%) tested for 49 genes that are commonly found on ECS, with cystic fibrosis (CFTR) being the most common (34/351) followed by fragile X (FMR1; 32/351); these represented the second and third most common genes tested in our practice (9.7% and 9.1% respectively). Of all patients doing PGT-M for ECS-related conditions, 46.4% (84/181) tested for 41 genes that are not detected by traditional or ethnicity-based carrier screening, with the most common being GJB2-related nonsyndromic hearing loss (the fourth most common condition tested in our practice, representing 6.6% of our total PGT-M volume), followed by 21-hydroxylase deficient congenital adrenal hyperplasia (CYP21A2) and familial Mediterranean fever (MEFV). There were eight patients (2.3%) who either were or could have been identified on our current 283-disease ECS panel but would have been missed on our prior 176-disease ECS panel. Eight patients did PGT-M for HLA matching, and three did non-disclosure PGT-M (two for Huntington’s disease/HTT and one for CADASIL/NOTCH3). 80/124 genes tested (64.5%) were unique to a single patient. PGT-M is performed for a wide range of genetic conditions, and nearly two-thirds of genes tested in our clinic were unique to a single patient. While most conditions tested are childhood-onset, BRCA1 is the most common gene tested by our patient population, and the proportion of patients testing for HC syndromes has doubled over the past three years. More than half of patients pursued PGT-M for conditions detectable through ECS but not through traditional carrier screening; however, increasing the ECS panel size by more than 100 conditions has only had a minor effect on PGT-M uptake.