Prenatal Sonographic Features of 22q11.2 Microdeletion Syndrome

Isolated polyhydramnios: Is a genetic evaluation of value?

OBJECTIVE

To analyze the risk for genetic aberrations and pregnancy outcomes in pregnancies with isolated polyhydramnios.

STUDY DESIGN

This was a retrospective study of singleton pregnancies complicated by isolated polyhydramnios that underwent genetic amniocentesis between 2016 and 2021. Clinical and laboratory data were collected and reviewed for these cases, including maternal demographics, prenatal sonographic findings, chromosomal microarray results, and pregnancy outcomes.

RESULTS

A total of 94 singleton pregnancies were included. Three (3.2%) cases with chromosomal abnormalities were detected, including 2 case of trisomy 21 and 1 of 22q21.1 microdeletion. One case was diagnosed as Prader-Willi syndrome caused by maternal uniparental disomy of chromosome 15. Perinatal death occurred in 1 case with severe polyhydramnios, and was retrospectively diagnosed as Bartter syndrome. Of the 90 infants survived, two were identified to have single gene disorders after birth by whole exome sequencing.

CONCLUSION

We first attempted to determine the value of exome sequencing in pregnancies with isolated polyhydramnios. Our results warrant more studies to evaluate advanced genetic testing technologies used in such pregnancies.

Central 22q11.2 deletion (LCR22 B-D) in a fetus with severe fetal growth restriction and a mother with severe systemic lupus erythematosus: Further evidence of CRKL haploinsufficiency in the pathogenesis of 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11.2 DS, MIM #188400) is the most common chromosomal microdeletion with an incidence of 1 in 4000 live births. 22q11.2 DS patients present with varying penetrance and a broad phenotypic spectrum including dysmorphic features, congenital heart defects, hypoplastic thymus and T-cell deficiency, and hypocalcemia. The typical deletion spans 3 Mb between 4 large blocks of repetitive DNA, known as low copy repeats (LCRs), on chromosome 22 (LCR22) A and D. This deletion is found in ~85% of 22q11.2 DS patients, while only 4-5% have central LCR22B-D (1.5 Mb) and LCR22C-D (0.7 Mb) deletions. We report on a prenatally diagnosed, inherited case of central LCR22B-D 22q11.2 DS, born to a 22-year-old female with multiple autoimmune disorders. These include Sjogren's-syndrome-related antigen A (SSA+) severe systemic lupus erythematosus (SLE) with cutaneous and discoid components and seronegative antiphospholipid syndrome. Amniocentesis was performed due to fetal growth restriction (FGR). FISH with TUPLE1 (HIRA) probe was normal; however, chromosomal microarray identified a ~737 kb heterozygous loss between LCR22B-D. Subsequently, the same deletion was identified in the mother, which included CRKL and 19 other genes but excluded HIRA and TBX1, the typical candidate genes for 22q11.2DS pathogenesis. This case explores how loss of CRKL may contribute to immune dysregulation, as seen in the multiple severe autoimmune phenotypes of the mother, and FGR. Our experience confirms the importance of thorough workup in individuals with reduced penetrance of 22q11.2 DS features or atypical clinical presentations.