Fetal Nephrology: A Quaternary Care Center Experience

Key Points

Specialized fetal centers see a highly complex subset of patients with CAKUT with a predominance of complex or syndromic disease. The mortality rate for fetuses with complex developmental anomalies and CAKUTs or bilateral CAKUTs is high. Prenatal genetic testing was highly variable with limited diagnostic utility while focused postnatal genetic testing had much higher yield.

Background

Congenital anomalies of the kidney and urinary tract (CAKUTs) represent 15%–20% of prenatally diagnosed abnormalities. Maternal characteristics, the frequency of various forms of kidney disease including CAKUT referred for prenatal nephrology consultation, and their perinatal outcomes are less well defined.

Methods

A retrospective chart review was performed of fetal CAKUT and other forms of kidney disease referred for prenatal nephrology consults at Texas Children's Hospital Fetal Center from January 1, 2012, to December 31, 2018.

Results

Two hundred seventeen prenatal nephrology consultations were performed during the study period, representing 4.7% of total Fetal Center referrals at a mean estimated gestational age of 25.2±5.7 weeks. Maternal characteristics were as follows: The mean age was 29.3±5.6 years; 14% had advanced maternal age; 10% had a family history of CAKUT or ESKD; 5% had diabetes mellitus; and 5% of pregnancies were in vitro fertilization-assisted. Fetal characteristics were as follows: 62.7% of fetuses were male and 16% had CAKUT associated with multiple congenital anomalies. The most common prenatal diagnoses were lower urinary tract obstruction in 71 (32.7%), unilateral renal agenesis or multicystic dysplastic kidney (MCDK) in 52 (24.9%), bilateral agenesis or MCDK in 22 (10.1%), and bilateral cystic kidney disease in 19 (8.8%). Seventy-six percent of patients received genetic counseling. One hundred forty-one (64.9%) patients had some form of prenatal genetic testing with a positivity rate of 5.7%. Postnatal characteristics were as follows: 61 (28.1%) patients were seen in prenatal consultation only and no follow-up was available. Of the remaining 156 pregnancies, 136 (86.3%) were viable and delivered at a mean gestational age of 35.2±3.8 weeks. Of these, 100 (64%) survived to discharge. Additional postnatal genetic testing was obtained in 27 infants with a positivity rate of 59%.

Conclusions

Overall perinatal mortality for this cohort as a whole was high (35.8%). While prenatal genetic testing had a limited diagnostic utility, targeted postnatal genetic testing had a much higher diagnostic yield.

Compound heterozygosity of a de novo submicroscopic deletion and an inherited frameshift pathogenic variant in the PKHD1 gene in a fetus with bilaterally enlarged and echogenic kidneys, enlarged abdomen and oligohydramnios

We present a fetus with bilaterally enlarged and echogenic kidneys. Prenatal testing detected compound heterozygosity for a 0.676 Mb de novo deletion and an inherited pathogenic variant in PKHD1. This is the first case of autosomal recessive polycystic kidney disease (ARPKD) with a prenatally detected disease-causing PKHD1 deletion.

Prioritization of Candidate Genes for Congenital Diaphragmatic Hernia in a Critical Region on Chromosome 4p16 using a Machine-Learning Algorithm

Wolf-Hirschhorn syndrome (WHS) is caused by partial deletion of the short arm of chromosome 4 and is characterized by dysmorphic facies, congenital heart defects, intellectual/developmental disability, and increased risk for congenital diaphragmatic hernia (CDH). In this report, we describe a stillborn girl with WHS and a large CDH. A literature review revealed 15 cases of WHS with CDH, which overlap a 2.3-Mb CDH critical region. We applied a machine-learning algorithm that integrates large-scale genomic knowledge to genes within the 4p16.3 CDH critical region and identified FGFRL1 , CTBP1 , NSD2 , FGFR3 , CPLX1 , MAEA , CTBP1-AS2 , and ZNF141 as genes whose haploinsufficiency may contribute to the development of CDH.

Reproductive genetic counseling challenges associated with diagnostic exome sequencing in a large academic private reproductive genetic counseling practice

OBJECTIVE

Diagnostic whole exome sequencing (WES) is rapidly entering clinical genetics, but experience with reproductive genetic counseling aspects is limited. The purpose of this study was to retrospectively review and report on our experience with preconception and prenatal genetic counseling for diagnostic WES.

METHOD

We performed a retrospective chart review over 34 months in a large private prenatal genetic counseling practice and analyzed data for referral indications, findings, and results of genetic counseling related to diagnostic WES.

RESULTS

Ten of 14 patients counseled about diagnostic WES for ongoing pregnancies pursued the test, resulting in identification of three pathogenic variants (30%). Five of 15 patients seeking counseling about familial WES results in an affected proband pursued prenatal diagnosis, resulting in identification of one affected fetus and five unaffected fetuses. We experienced challenges related to complexity and uncertainty of results, turnaround time, cost and insurance overage, and multidisciplinary fetal care coordination.

CONCLUSION

Despite having experienced complexity and identified challenges of the reproductive genetic counseling, availability of diagnostic WES contributed important information that aided in prenatal care planning and decision-making. Future enhanced provider education and larger studies to systematically study the integration of WES in reproductive genetic counseling and prenatal care will be important.

Regional localization and abundance of calcitonin gene-related peptide receptors in guinea pig heart

Calcitonin gene-related peptide (CGRP) is a neurotransmitter that is released within the heart during myocardial ischemia. The present study was done to determine the regional localization and abundance of CGRP receptors in the guinea pig heart. CGRP binding sites in 20 microm frozen sections of heart were labeled using [125I]CGRP. Non-specific binding was determined in the presence of 1 microm unlabeled CGRP or CGRP(8-37). Significant amounts of specific CGRP binding were identified in atrial and ventricular myocardium, all portions of the conducting system, coronary arteries, the aorta and pulmonary trunk and intracardiac ganglia. Specific binding of CGRP to the left atrium was two-fold higher than binding to the right atrium (0.667+/-0.052 v 0.340+/-0.029 fmol/mg tissue, n=5, CGRP(8-37)group). In contrast to the atria, a lower and uniform density of CGRP receptors occurred in contractile tissue of the ventricular myocardium (e.g. 0.239+/-0.013 fmol/mg left ventricle, n=5). The highest concentration of CGRP receptors in guinea pig cardiac tissue occurred at the bundle of His and the bundle branches (0.752+/-0.087 and 0.713+/-0.138 fmol/mg tissue, respectively, n=5). CGRP receptors were localized to coronary vessels throughout the heart and to the ascending aorta and pulmonary trunk. Lastly, intracardiac ganglia exhibited moderate levels of specific [125I]CGRP binding (0.475+/-0.043 fmol/mg, n=5). These findings support the concept that CGRP can have direct effects on atrial and ventricular function as well as coronary flow. The high density of CGRP receptors in the distal conducting system and the presence of CGRP receptors in intracardiac ganglia further suggest that CGRP could have important effects on cardiac conduction velocity and parasympathetic regulation of the heart.