Understanding Fetal Cystic Hygroma: Diagnosis and Genetic Testing

Expert Reviewed By: ⁠Dr. Brandon Colby MD

Fetal cystic hygroma is a rare congenital malformation characterized by fluid-filled sacs that develop in the lymphatic system. It usually appears as a swelling on the neck or head of the fetus and can be detected during prenatal ultrasound examinations. The condition is often associated with chromosomal abnormalities, such as Noonan Syndrome, and can lead to serious complications, including fetal hydrops and stillbirth. Early diagnosis and genetic testing can help guide treatment and management options, providing valuable information for expecting families.

Understanding Fetal Cystic Hygroma

Cystic hygroma occurs when the lymphatic system, responsible for transporting fluid and immune cells throughout the body, fails to develop properly. This can lead to the formation of fluid-filled sacs, or cysts, which can cause swelling and other complications. The severity of cystic hygroma can vary, with some cases resolving spontaneously while others require invasive treatment or result in severe outcomes.

Several factors can contribute to the development of fetal cystic hygroma, including genetic mutations and environmental influences. Chromosomal abnormalities, such as those associated with Noonan Syndrome, are often implicated in the condition. In fact, a study published in the Journal of Maternal-Fetal & Neonatal Medicine highlights the importance of analyzing the PTPN11 gene in fetuses with cystic hygroma and normal karyotype, as it is associated with Noonan Syndrome.

Diagnosing Fetal Cystic Hygroma

Fetal cystic hygroma is typically detected during routine prenatal ultrasound examinations. If the condition is suspected, further diagnostic tests may be performed, including:

• Targeted ultrasound to assess the extent of the cystic hygroma and identify any associated anomalies
• Chromosomal analysis through amniocentesis or chorionic villus sampling (CVS) to identify any chromosomal abnormalities
• Fetal echocardiography to evaluate the fetal heart structure and function

Genetic Testing for Fetal Cystic Hygroma

Genetic testing can be a valuable tool in understanding the underlying causes of fetal cystic hygroma and guiding treatment options. It can help identify chromosomal abnormalities and genetic mutations associated with the condition, providing crucial information for expecting families and healthcare providers.

Exome Sequencing in Nonimmune Hydrops Fetalis

Nonimmune hydrops fetalis (NIHF) is a severe complication of fetal cystic hygroma, characterized by abnormal fluid accumulation in the fetus. A study published in the New England Journal of Medicine evaluated the diagnostic yield of exome sequencing in detecting genetic variants in unexplained cases of NIHF. The study found that exome sequencing identified a diagnostic genetic variant in 29% of cases, highlighting the potential of this technique in prenatal diagnosis.

Phenotypic Discordance in Monozygotic Twins

Genetic testing can also help explain phenotypic discordance in monozygotic twins, as demonstrated by a case report published in the Journal of Obstetrics and Gynaecology Research. The report presents phenotypically discordant monochorionic twins with the same genotype, highlighting possible causes for phenotypic discordance in monozygotic twins.

Conclusion

Fetal cystic hygroma is a complex condition with varying causes and outcomes. Early diagnosis and genetic testing can provide valuable information for expecting families and healthcare providers, helping to guide treatment and management decisions. By understanding the underlying genetic factors and utilizing advanced diagnostic techniques, it is possible to improve the prognosis and quality of life for affected individuals.

About The Expert Reviewer

Dr. Brandon Colby MD is a US physician specializing in the personalized prevention of disease through the use of genomic technologies. He’s an expert in genetic testing, genetic analysis, and precision medicine. Dr. Colby is also the Founder of  and the author of ⁠⁠Outsmart Your Genes.

Dr. Colby holds an MD from the Mount Sinai School of Medicine, an MBA from Stanford University’s Graduate School of Business, and a degree in Genetics with Honors from the University of Michigan. He is an Affiliate Specialist of the American College of Medical Genetics and Genomics (⁠⁠ACMG), an Associate of the American College of Preventive Medicine (⁠⁠ACPM), and a member of the National Society of Genetic Counselors (⁠NSGC)