Prenatal evaluation of genetic variants in fetuses with small head circumference: A single-center retrospective study

Prenatal phenotype of PNKP-related microcephaly, seizures, and developmental delay: A case report and literature review

RATIONALE

Microcephaly, epilepsy, and developmental delay (MCSZ) is a rare neurodevelopmental disorder associated with autosomal recessive inheritance of mutations in the polynucleotide kinase 3'-phosphatase (PNKP) gene. Prompt identification and management are essential, as delayed diagnosis or intervention may result in severe complications or mortality. In this case, prenatal screening in the second trimester detected fetal microcephaly with a gradual decline in head circumference, prompting the decision to terminate the pregnancy. Subsequent genetic analysis of the fetal tissue confirmed the presence of compound heterozygous mutations in the PNKP gene.

PATIENT CONCERNS

The patient, a 34-year-old remarried female with no history of consanguineous marriage, underwent 2 mid-trimester termination procedures due to fetal microcephaly and sought counseling for reproductive assistance.

DIAGNOSES

The patient's carrier status for PNKP mutations was ascertained through whole-exome sequencing of the termination tissue and molecular genetic testing for monogenic disorders. The terminated fetus was diagnosed with MCSZ, a condition associated with compound heterozygous mutations in the PNKP gene.

INTERVENTIONS

Fetal microcephaly was identified via mid-trimester prenatal ultrasound, leading to the termination of the pregnancy during the same trimester. Subsequent genetic analysis of the immediate family revealed compound heterozygous mutations in the PNKP gene as the underlying cause of MCSZ. Genetic counseling was provided, followed by 1 cycle of preimplantation genetic testing for monogenic.

OUTCOMES

The patient carried the heterozygous c.1188 + 1G > A PNKP mutation, whereas her husband carried the heterozygous c.976G > A PNKP mutation. The fetus was found to have compound heterozygous mutations c.976G > A and c.1188 + 1G > A. After counseling, the couple underwent 1 cycle of preimplantation genetic testing for monogenic, unfortunately, no pregnancy occurred after the 2 embryos were transferred.

LESSONS

MCSZ, a condition caused by PNKP mutations, is exceedingly rare. Women with a history of adverse pregnancy outcomes should undergo close monitoring during prenatal checkups. If fetal microcephaly is detected, it is essential to strictly follow obstetric guidelines for prenatal care, such as comprehensive cranial magnetic resonance imaging and genetic testing for confirmation. Avoidance of consanguineous marriages is advised. Early detection and timely intervention are key to preventing adverse pregnancy outcomes.

Chromosomal microarray testing yield in 829 cases of microcephaly: a clinical characteristics-based analysis for prenatal and postnatal cases

INTRODUCTION

Microcephaly, characterized by abnormal head growth, can often serve as an initial indicator of congenital, genetic, or acquired disorders. In this study, we sought to evaluate the effectiveness of chromosomal microarray (CMA) testing in detecting abnormalities in both prenatal and postnatal cases of microcephaly.

MATERIALS AND METHODS

CMA Testing: We conducted CMA testing on 87 prenatally-detected microcephaly cases and 742 postnatal cases at a single laboratory. We evaluated the CMA yield in relation to specific clinical characteristics.

RESULTS

In prenatal cases, pathogenic and likely pathogenic (LP) results were identified in 4.6% of cases, a significantly higher rate compared to low-risk pregnancies. The male-to-female ratio in this cohort was 3, and the CMA yield was not influenced by gender or other clinical parameters. For postnatal cases, the CMA yield was 15.0%, with a significantly higher detection rate associated with dysmorphism, hypotonia, epilepsy, congenital heart malformations (CHM), learning disabilities (LD), and a history of Fetal growth restriction (FGR). No specific recurrent copy number variations (CNVs) were observed, and the rate of variants of unknown significance was 3.9%.

CONCLUSIONS

The yield of CMA testing in prenatal microcephaly is lower than in postnatal cases (4.6% vs. 15%). The presence of microcephaly, combined with dysmorphism, hypotonia, epilepsy, CHD, LD, and FGR, significantly increases the likelihood of an abnormal CMA result.