Introduction

Loeys-Dietz syndrome (LDS) is a rare genetic disease that was identified by paediatric geneticists Dr. Bart L. Loeys and Harry C. Dietz in 2005.¹ It is a genetic disorder passed down in an autosomal dominant manner, meaning that a child has to inherit only 1 mutated gene for them to be diagnosed with the condition. Loeys-Dietz syndrome leads to abnormalities in connective tissue found in the heart, blood vessels, joints, bones, skin, intestines, spleen, and uterus.² This syndrome is similar to Marfan’s syndrome, but has some differences in the clinical presentation. The main characteristic feature is enlargement of the aorta (the blood vessel supplying blood from the heart to the rest of the organs), and this condition poses a serious risk of mortality, primarily due to potential aortic rupture; hence, it needs appropriate management.³ Therefore, early diagnosis is crucial in the management of LDS, especially during the prenatal or neonatal stage, to prevent undue complications. 

Genetic pathway of loeys-dietz syndrome

The condition results from a random mutation in one copy of the affected gene. These mutations or changes take place in any of the TGF-Beta (Transforming growth factor) signal pathways. The genes involved are TGFBR1, TGFBR2, SMAD2, SMAD3, TGFB2, and TGFB3.⁴ The proteins encoded by these genes are responsible for cell growth, division, and tissue repair. This condition is seen in all ethnic groups, and if the mother or father has LDS, each of their children has a high chance of inheriting the gene mutation. If the affected person is the first person in the family to be diagnosed with the condition, then it is inferred to be the mutation that happened in the egg or sperm during conception.⁵

Major clinical features of LDS

This is a multisystem disorder characterised by a broad range of complex multi-system manifestations.⁶ Hence, vigilant monitoring is essential to prevent the risk of complications. The prominent clinical features include:

• Aneurysm of all the arteries, especially in the aorta.
• Widely set eyes 
• Cleft palate / Enlarged uvula
• Joint laxity and translucent skin
• Abnormal shape of the skull
• Hernias
• Skeletal abnormalities: clubfoot, scoliosis, pectus deformities, cervical spine instability
• Congenital heart defects
• Allergies

Prenatal diagnosis

Diagnosis of LDS involves clinical correlation with imaging and genetic testing. Early diagnosis (if possible before birth) is critical to extend the life span of the affected individual. An accurate diagnosis can help get early treatment and supervision. Going through the history thoroughly in the initial phase has to be done, such as enquiring about the family of both parents to rule out the risk of LDS. LDS and other genetic disorders should be considered, and further investigation should be carried out, if abnormalities like Intrauterine growth restriction, cleft palate or arterial tortuosity are detected.⁷ 

Diagnostic tools

Ultrasound

The presence of foetal aortic dilatation is a significant prenatal indicator suggestive of LDS. Cranial and skeletal deformities such as pectus deformities, scoliosis and club foot, along with abnormal uvula and cleft palate, can be identified in the foetus with the help of ultrasonography (USG). In some patients, slight dilation of the pulmonary artery may be observed. In some cases, inguinal hernias and translucent skin are also seen.

Foetal echocardiography

Assessment of aortic root size and heart defects can be detected with a foetal echocardiogram. In LDS, dilatation and tortuosity of the aorta is present in childhood; however, it can even be observed in the uterine stage. In some foetuses, cardiac septal defects are also observed. If LDS is suspected, the case should be referred to the paediatric cardiology unit for further confirmation. A 3D echocardiography is the latest advancement in imaging technology, due to which, it is possible to visualise complex cardiac anatomy, measure vessel and chamber sizes and assess functions of valves and regurgitation.⁹

Foetal MRI

MRI can be advised, in select cases, to better visualise skeletal abnormalities and to assess neurological features. Additionally high resolution cardiac imaging and tissue characterisation can be done, in order to better understand cardiac anatomy and function, as well as observe the presence of any scarring on the heart. (“Advanced Cardiac Imaging in Loeys-Dietz Syndrome”)

Genetic testing

If the USG and MRI show the characteristic features of LDS, then, as a conclusive test, invasive methods such as amniocentesis and chorionic villus sampling may be undertaken with the consent of the pregnant woman. Genetic tests include serial single-gene testing, where genes in which mutations can cause the disease of interest are examined one by one. Subsequently, a comprehensive genomic testing is done to rule out other genetic conditions if it shows similar features of inherited conditions in the USG.¹⁰ Additionally, with genetic tests, the risk of future pregnancies can be interpreted. Pre-implantation genetic diagnosis can be done if the parents opt for an artificial reproductive technique to ensure the implantation of a genetically healthy embryo, free from inherited diseases.

Neonatal diagnosis

Clinical assessment at birth and confirmatory testing

The child should be examined for the physical signs of Loeys-Dietz Syndrome, such as dysmorphic face, cleft palate, hypermobility and loose joints, skin laxity, and significant scoliosis. If any of these features are identified, then an immediate cardiovascular evaluation has to be done to examine the aorta, as tortuosity and aneurysm of the aortic roots and arteries are the typical features of LDS. Regular assessment with imaging tests like MRI and CT angiography is very important in LDS to monitor disease progression. Cardiac MRI enables the accurate imaging of aortic wall thickness and visualisation of aortic aneurysms. AI-assisted echocardiography is emerging as an option for more complex imaging, which will be particularly useful in LDS management.  Genetic testing via blood samples can be done for confirmation of LDS at any stage, with a positive result showing a pathogenic variant. 

Differential diagnosis of LDS

LDS shares several clinical features with other connective tissue disorders, which can cause confusion in the diagnosis. LDS is commonly confused with Marfan Syndrome and Ehlers-Danlos Syndrome, due to the similarities in multiple symptoms such as aortic dilatation, skeletal deformities, and joint hypermobility.

An early diagnosis is very crucial in LDS, as this condition needs more attention and requires immediate surgery because of rapid dilatation and rupture of the aorta. A missed diagnosis can lead to complications which can be life-threatening to the affected individual. Along with clinical findings, a comprehensive genetic test should be done to rule out other genetic connective tissue disorders.

Importance of genetic counselling

Providing genetic counselling prior to and following confirmatory genetic tests is a crucial component of patient care. A genetic counsellor can help with familial education on the nature of the disease, inheritance, tests required, surveillance of the patient, risk factors, and health management. 

A genetic counsellor plays a vital role in this genetic condition, such as providing information regarding the risk of transmission to their next generation. Parents can also be educated about different reproductive options, including ART, where pre-implantation genetic diagnosis can be done. Through this approach, a healthy embryo without any genetic inheritance can be injected to the uterus, thereby giving birth to a healthy progeny.¹¹

Most of the cases reported have been identified during the neonatal stage. So, a genetic test at this phase can confirm the diagnosis and special monitoring. Immediate surgery, if required, can be performed on the baby. This helps to increase the life expectancy of the affected child.

Summary

Loeys-Dietz Syndrome is a recently recognised autosomal connective tissue disorder. It is caused due to the mutations of genes which are associated with the TGF-Beta (Transforming Growth Factor) signalling pathway. The hallmark feature of LDS is tortuosity and aneurysm of the aorta. The aortic dilatation may cause rupture and further complications, thereby making this syndrome potentially life-threatening. However, an early diagnosis and proper intervention improve the quality of life and increase the life expectancy in affected individuals. 

Obstetricians, neonatologists, and genetic counsellors play an important role in the early detection of this syndrome. Currently, the advancement of imaging technologies such as MRI, CT, and angiography, along with genetic tests, helps with an accurate diagnosis and monitoring of LDS. If any patient presents with arterial dilatation and dissection, genetic tests should be done to find the diagnosis, and, if it confirm mutations, family members should also undergo tests to rule out the possibility of LDS.

FAQs

Is genetic testing a necessary step in confirming the diagnosis of loeys-dietz syndrome?

Yes, for a confirmatory diagnosis, a genetic test is required. Especially if the clinical features are incomplete.

What is the significance of early detection in the management of loeys-dietz syndrome?

Early diagnosis of LDS allows monitoring of blood vessels and cardiac functions. Also, timely intervention and surgical corrections can be performed under the required conditions. 

Does every case of cleft palate indicate the presence of loeys-dietz syndrome?

Not necessarily. It doesn’t always mean that a person has Loeys-Dietz Syndrome, and not every patient with Loeys-Dietz Syndrome has a cleft palate.¹²

Can individuals diagnosed with loeys-dietz syndrome maintain a normal lifestyle?

Absolutely, an early diagnosis and regular surveillance help them to live a normal life. But regular follow-ups with cardiologists, geneticists, and other speciality doctors are required as it is a condition involving multiple systems. Additionally, lifestyle modifications have to be done to prevent arterial rupture, such as avoiding contact sports and heavy exercises.