Clinically significant findings in a decade-long retrospective study of prenatal chromosomal microarray testing.

BACKGROUND: Chromosomal microarray (CMA) is commonly utilized in the obstetrics setting. CMA is recommended when one or more fetal structural abnormalities is identified. CMA is also commonly used to determine genetic etiologies for miscarriages, fetal demise, and confirming positive prenatal cell-free DNA screening results. METHODS: In this study, we retrospectively examined 523 prenatal and 319 products-of-conception (POC) CMA cases tested at Nationwide Children's Hospital from 2011 to 2020. We reviewed the referral indications, the diagnostic yield, and the reported copy number variants (CNV) findings. RESULTS: In our cohort, the diagnostic yield of clinically significant CNV findings for prenatal testing was 7.8% (n = 41/523) compared to POC testing (16.3%, n = 52/319). Abnormal ultrasound findings were the most common indication present in 81% of prenatal samples. Intrauterine fetal demise was the common indication identified in POC samples. The most common pathogenic finding observed in all samples was isolated trisomy 21, detected in seven samples. CONCLUSION: Our CMA study supports the clinical utility of prenatal CMA for clinical management and identifying genetic etiology in POC arrays. In addition, it provides insight to the spectrum of prenatal and POC CMA results as detected in an academic hospital clinical laboratory setting that serves as a reference laboratory.

Prenatal Genetic Testing and Screening: A Focused Review.

Given the advancements in prenatal testing, child neurologists are becoming involved in earlier stages of patient care, often being consulted during the gestational stage rather than during the postnatal period. Thus, it is essential that pediatric neurologists understand the strengths and limitations of prenatal testing when counseling families. In this review we separate prenatal testing into screening and diagnostic testing. On the one hand, screening testing is noninvasive and does not have an increased risk for miscarriage. Diagnostic tests, on the other hand, are invasive and include chorionic villus sampling and amniocentesis. Understanding that screening tests are not diagnostic is imperative, therefore, attention should be placed on the positive and negative predictive values when interpreting results within the clinical context. Given their invasive nature, prenatal diagnostic tests increase the risk for complications such as miscarriage. Diagnostic tests include biochemical marker testing, enzyme testing, karyotype, microarray, whole exome sequencing, and whole genome sequencing. With each test, pretest and post-test counseling is crucial for informed decision making, and the strengths and limitations should be discussed when obtaining consent. Prior to obtaining testing, clinicians must consider unexpected and unrelated findings of testing and must acknowledge that the patient always has the option to decline the test.

Phenotypic Spectrum in a Family Sharing a Heterozygous KCNQ3 Variant.

BACKGROUND AND PURPOSE: Mutations in KCNQ3 have classically been associated with benign familial neonatal and infantile seizures and more recently identified in patients with neurodevelopmental disorders and abnormal electroencephalogram (EEG) findings. We present 4 affected patients from a family with a pathogenic mutation in KCNQ3 with a unique constellation of clinical findings. METHODS: A family of 3 affected siblings and mother sharing a KCNQ3 pathogenic variant are described, including clinical history, genetic results, and EEG and magnetic resonance imaging (MRI) findings. RESULTS: This family shows a variety of clinical manifestations, including neonatal seizures, developmental delays, autism spectrum disorder, and anxiety. One child developed absence epilepsy, 2 children have infrequent convulsive seizures that have persisted into childhood, and their parent developed adult-onset epilepsy. An underlying c.1091G>A (R364H) variant in KCNQ3 was found in all affected individuals. CONCLUSIONS: The phenotypic variability of KCNQ3 channelopathies continues to expand as more individuals and families are described, and the variant identified in this family adds to the understanding of the manifestations of KCNQ3-related disorders.