Abstract
BackgroundThe 22q11.2 deletion syndrome is the most common microdeletion syndrome in livebirths, but data regarding its incidence in other populations is limited and also include ascertainment bias. This study was designed to determine the incidence of the 22q11.2 deletion in miscarriage samples sent for clinical molecular cytogenetic testing.ResultsTwenty-six thousand one hundred one fresh product of conception (POC) samples were sent to a CLIA- certified, CAP-accredited laboratory from April 2010–-May 2016 for molecular cytogenetic miscarriage testing using a single-nucleotide polymorphism (SNP)-based microarray platform. A retrospective review determined the incidence of the 22q11.2 deletion in this sample set. Fetal results were obtained in 22,451 (86%) cases, of which, 15 (0.07%) had a microdeletion in the 22q11.2 region (incidence, 1/1497). Of those, 12 (80%) cases were found in samples that were normal at the resolution of traditional karyotyping (i.e., had no chromosome abnormalities above 10 Mb in size) and three (20%) cases had additional findings (Trisomy 15, Trisomy 16, XXY). Ten (67%) cases with a 22q11.2 deletion had the common ~3 Mb deletion; the remaining 5 cases had deletions ranging in size from 0.65 to 1.5 Mb. A majority (12/15) of cases had a deletion on the maternally inherited chromosome. No significant relationship between maternal age and presence of a fetal 22q11.2 deletion was observed.ConclusionsThe observed incidence of 1/1497 for the 22q11.2 deletion in miscarriage samples is higher than the reported general population prevalence (1/4000–1/6000). Further research is needed to determine whether the 22q11.2 deletion is a causal factor for miscarriage.
Highlights
The 22q11.2 deletion syndrome is the most common microdeletion syndrome in livebirths, but data regarding its incidence in other populations is limited and include ascertainment bias
The remaining 3650 (14%) cases were excluded from the analysis due to having maternal cell contamination (MCC) (n = 3549, 13.6%) or incomplete results (n = 101, 0.4%; Fig. 1)
A 22q11.2 deletion was identified in three cases, one with a typical 3.5 Millions of base pairs (Mb) deletion and a finding of Klinefelter syndrome (47,XXY), one with a nested 1.5 Mb deletion and a finding of trisomy 15, and the third with a rarer 0.65 Mb deletion and a finding of trisomy 16 (Table 1)
Summary
The 22q11.2 deletion syndrome is the most common microdeletion syndrome in livebirths, but data regarding its incidence in other populations is limited and include ascertainment bias. Recent studies performed in prenatal cohorts have indicated a higher prenatal incidence of ≥1/1000 for the 22q11.2 deletion [6,7,8]. Given that these studies were retrospective and involved a substantial percentage of cases referred for invasive diagnostic procedures (e.g., due to ultrasound anomalies), these studies are subject to ascertainment bias. In the absence of a newborn screening program for the detection of 22q11.2 deletion syndrome, true incidence of the deletion remains unknown
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