Prenatal diagnosis of familial transmission of 17q12 microduplication associated with no apparent phenotypic abnormality

Road to a rare diagnosis: Description of novel unbalanced translocation causing partial trisomy 17p

Trisomy 17 is a rare chromosomal disorder. Existing literature on the topic is limited and mostly refer to mosaic Trisomy 17 cases. Our report summarizes the 70‐day clinical course of a late preterm neonate with partial Trisomy 17p karyotype 46,XY,der(14)t(14;17)(p11.1;p11.2) dpat. Trisomy 17 due to unbalanced translocation is rare, and our case elaborates the clinical presentation with intestinal malfunction without any anatomical pathology and urethral diverticulum and the ethical dilemma in decision‐making. The male proband was born at 35 weeks with antenatal findings of multiple neurological and other abnormalities such as cystic hygroma, absent corpus collosum, high riding third ventricle, absent cavum septum pellucidum, indented occiput, absent ductus venous, and intrauterine growth restriction. The postnatal findings included significant facial dysmorphisms with short palpebral fissures, hypertelorism, low set ears, micrognathia, hirsutism, and single palmar creases, central hypotonia, and hyperreflexia of upper limbs bilaterally. Genital‐urinary assessment revealed a urinary diverticulum and significantly underdeveloped scrotum with undescended testes. Infant had excessive irritability and resistance to sleep despite increasing doses of analgesia and sedation, and persistent respiratory and feeding difficulties. Enteral nutrition could not be established due to profuse and persistent diarrhea, necessitating use of total parenteral nutrition. Microarray assay exhibited a pathogenic copy number gain of approximately 21.4 Mb of chromosome region 17p13.3p11.2. Follow‐up chromosome analysis and FISH revealed an abnormal male karyotype with a derivative chromosome 14, resulting from an unbalanced translocation between the short arm of one chromosome 14 and the short arm of one chromosome 17, effectively resulting in trisomy 17p11.2. It was derived from a paternal balanced t(14;17)(p11.1;p11.2) as shown by chromosome analysis and FISH studies. The rarity of this chromosomal disorder contributed to difficulty with prognosis and led to bioethical dilemma regarding life‐sustaining measures and quality of life. Through shared decision‐making processes and in consideration of poor prognosis, parents decided to withdraw life‐sustaining care and the proband died at postnatal day of life 70.

Prenatal ultrasound phenotypic and genetic etiology of the 17q12 microduplication syndrome

BACKGROUND

Several studies have reported on the clinical phenotype of the 17q12 microduplication syndrome, a rare autosomal dominant genetic disorder, in children and adults, but few have reported on its prenatal diagnosis. This study analyzed the prenatal ultrasound phenotypes of the 17q12 microduplication syndrome to improve the understanding, diagnosis, and monitoring of this disease in fetuses.

METHODS

A retrospective analysis of 8,200 pregnant women who had received an invasive antenatal diagnosis at tertiary referral hospitals between January 2016 and August 2021 was performed. Amniotic fluid or cord blood was sampled from the pregnant women for karyotyping and chromosome microarray analysis (CMA).

RESULTS

The CMA revealed microduplication in the 17q12 region of the genome in five fetuses, involving fragments of about 1.5-1.9 Mb. Five fetuses with the 17q12 microduplication syndrome had different prenatal ultrasound phenotypes, including duodenal obstruction (two fetuses); mild ventriculomegaly, dysplasia of the septum pellucidum, agenesis of the corpus callosum (one fetus); and a strong echo in the left ventricle only (one fetus). The ultrasound phenotype of one fetus was normal. Among the five fetuses with the 17q12 microduplication syndrome, the parents of three refused CNV segregation analysis, while CNV segregation analysis was performed for the remaining two fetuses to confirm whether the disorder was inherited maternally or paternally, with normal phenotypes. After genetic counseling, the parents of those two fetuses chose to terminate the pregnancy, while the parents of the three unverified fetuses continued the pregnancy, with normal follow-up after birth.

CONCLUSION

Although prenatal ultrasound phenotypes in fetuses with the 17q12 microduplication syndrome are highly variable, our study has highlighted the distinct association between duodenal obstruction and the 17q12 microduplication syndrome. Understanding the relationship between the pathogenesis of the 17q12 microduplication in prenatal ultrasound phenotypes and its long-term prognosis will contribute to better genetic counseling concerning the 17q12 microduplication syndrome, which is still a challenge.

Prenatal features of 17q12 microdeletion and microduplication syndromes: A retrospective case series

OBJECTIVE

To present the experience on prenatal features of 17q12 microdeletion and microduplication syndromes.

MATERIALS AND METHODS

Prenatal chromosomal microarray analysis (CMA) were conducted between January 2015 and December 2018 at a single Chinese tertiary medical centre. Information of cases identified with 17q12 microdeletion or microduplication syndromes were retrospectively collected. Foetal ultrasonographic findings were reviewed, and other information about the gestation week at diagnosis, inheritance and pregnancy outcomes were also included.

RESULTS

Ten pregnancies with 17q12 microdeletion and 4 with 17q12 microduplication were identified. The copy number variation (CNV) sizes were 1.39-1.94 Mb in the deleted cases and 1.42-1.48 Mb in the duplicated cases, respectively. All the duplicated and deleted regions included HNF1B and LHX1 genes. Most individuals with 17q12 deletion presented kidney anomalies (9/10), with renal hyperechogenicity being the most common finding (7/10). Fetuses with 17q12 duplication presented a wide phenotypic spectrum, including "double bubble" sign, structural anomalies of the heart and growth anomalies.

CONCLUSIONS

Our experience further demonstrated the high correlation between 17q12 microdeletion and renal anomalies especially hyperechogenic kidneys. Structural anomalies of the heart were newly identified phenotypes of 17q12 duplication during prenatal period. Besides, growth anomalies and duodenal atresia might be associated with the duplication.

Prenatal diagnosis of 17q12 microdeletion and microduplication syndrome in fetuses with congenital renal abnormalities

Background

Copy number variations (CNVs) involving the 17q12 region are associated with a broad range of clinical phenotypes. Deletion of the 17q12 chromosome results in structural or functional abnormalities in the kidney and urethra, type 5 diabetes (MODY5), and neurodevelopmental or neuropsychiatric disorders. Microduplication of 17q12 is rare and is associated with an increased risk of epilepsy and mental retardation. We studied the prenatal diagnosis of 17q12 microduplication and microdeletion syndrome in fetuses with congenital renal abnormalities.

Case presentation

We conducted a retrospective analysis of prenatal diagnoses in our hospital from January 2016 to April 2018. Abnormal renal ultrasound findings were present in 126 fetuses and the incidence of chromosomal abnormalities was 10.32%(13/126). Conventional karyotyping detected 7 of 126 fetuses as aneuploid (5.56%). In addition, chromosome microarray analysis (CMA) detected 6 fetuses(4.76%) with copy number variations (CNVs), of which 5 were shown to have 17q12 microdeletion syndrome and 1 had 17q12 microduplication syndrome. We followed up these pregnant women. The results of the testing had a significant impact on pregnancy outcome. The phenotypes of 17q12 microdeletions and microduplications vary widely, affecting patients in different ways, such as language delays, social deficiencies, and even abortion.

Conclusions

The characteristics of 17q12 microdeletions and microduplications are so vague that the condition is often misdiagnosed or missed. This study demonstrated that karyotype analysis combined with CMA can significantly improve the diagnostic rate in prenatal diagnosis of CNVs, which can provide evidence for genetic counseling in such pregnancies.