Loeys-Dietz syndrome symptoms & causes in children

While the word “syndrome” can be a frightening one, it simply refers to a group of symptoms that occur together.

  • When a doctor says that your child has Loeys-Dietz syndrome, he means that your child has some or all of the symptoms associated with the condition.
  • Some children who have Loeys-Dietz syndrome have all the symptoms that we discuss below, while others only have one or two.

For more information about the causes and symptoms of Loeys-Dietz syndrome, as well as what they mean for your child, read on.

How common is it?

Loeys-Dietz syndrome is a fairly rare genetic condition. Until recently, Loeys-Dietz syndrome was called Marfan syndrome type 2. Only a small percentage of the one in 5,000 to 10,000 children who have Marfan syndrome have this variety.

When does it appear?

Loeys-Dietz syndrome is present at birth but, because it can resemble other conditions, it may not be diagnosed immediately.

  • If your child has any of the characteristic facial features [LINK to Signs and Symptoms section] of Loeys-Dietz syndrome, your pediatrician may notice them and recommend further testing.
  • Other children with the syndrome are diagnosed when they come in for evaluation of skeletal or cardiac problems, such as a heart murmur or other medical condition.

Who gets Loeys-Dietz syndrome?

It’s equally common in boys and girls.

Why is Loeys-Dietz syndrome a problem?

Kids with Loeys-Dietz syndrome have abnormal connective tissue, which can lead to problems in many different parts of the body. Here are some of the major problems a child with Loeys-Dietz syndrome can have:

  • Arterial aneurysms are the main concerns for children with Loeys-Dietz syndrome. The condition causes aneurysms (or bulges) in the vessel wall, which then becomes weakened and can burst, leading to a life-threatening emergency. This can involve the aorta (the major artery arising from the heart) or other blood vessels, such as those in the brain.
  • If your child has been diagnosed with Loeys-Dietz syndrome, it’s essential that he be monitored continually by a doctor, because these aneurysms tend to rupture at a young age — and at a size smaller than seen in children with Marfan syndrome.
  • Your child may have a variety of gastrointestinal problems, such as difficulty absorbing food and chronic diarrhea, abdominal pain, and gastrointestinal bleeding and inflammation. Children with Loeys-Dietz syndrome are also more likely to have food allergies than unaffected children.
  • Another complication can be instability in the vertebrae directly below the skull (cervical vertebrae). A small number of children with Loeys-Dietz syndrome need surgery to prevent slippage of the bones around their spinal cord. They can have other skeletal problems such as loose joints, scoliosis (curvature of the spine) and chest wall deformities (depression or protrusion of the breast bone).

When should we see a doctor?

As part of your child’s ongoing care, your doctor should regularly monitor your child for aneurysms. See the Treatment & Care section for more information.

  • If your child has been diagnosed with Loeys-Dietz syndrome and seems to be having intense or prolonged pain—anywhere in his body—he might be experiencing the dissection of an aneurysm. You should go to the emergency room immediately.

Causes of Loeys-Dietz syndrome

Loeys-Dietz syndrome is a genetic disorder caused by a mutation (gene change) in one of the genes in charge of the formation of connective tissue that connects and supports other tissues like skin, muscle and bones. It’s sometimes referred to as the “glue” that holds the body together.

How is Loeys-Dietz syndrome inherited?

Loeys-Dietz syndrome is an autosomal dominant condition, which means that a child need only have one abnormal copy of the responsible gene to have the condition. (Each of us has two copies of each gene, with the exception of genes on the X chromosome in boys.) In about 25 percent of cases, an affected child has inherited a copy of the abnormal gene from an affected parent. In the other 75 percent, the change in the gene has arisen anew in the affected child.

If the parent is found to have the abnormal gene, there is a 50 percent chance that the next child will also have it. If neither parent has the abnormal gene and is unaffected, then the risk to other children is low.

  • If you have Loeys-Dietz syndrome yourself and want to have children, consider discussing your family plans with a genetic counselor who can help you understand the implications of the syndrome for your children.

Signs and symptoms of Loeys-Dietz syndrome

Loeys-Dietz syndrome affects different kids in different ways. Not all children have all the signs and symptoms listed below. Your child’s pediatrician will be best able to determine whether your child should be evaluated by a geneticist for Loeys-Dietz syndrome.

Here are some of the more common signs and symptoms of Loeys-Dietz syndrome, organized by the part of your child’s body they affect:;

Heart and blood vessels

  • twisting or spiraled arteries
  • dilated (or enlarged) arteries—can lead to life-threatening aneurysms if they rupture
  • congenital heart defects like atrial septal defect


  • long fingers and toes
  • clubfoot
  • scoliosis (curvature of the spine)    
  • loose joints that are abnormally flexible
  • pectus excavatum—sometimes called “funnel chest” or “sunken chest”
  • pectus carinatum—sometimes called “pigeon breast”


  • hypertelorism—widely spaced eyes
  • blue sclerae—blue tinge to the whites of the eyes


  • easy bruising and scarring
  • skin that feels especially soft and is translucent in places

Head and face

  • craniosynostosis — premature closing of the sutures in the skull, which can lead to increased skull pressure and facial abnormalities
  • small or receding chin
  • flat cheek bones
  • split uvula (the tissue that hangs down in the back of the throat is divided)
  • cleft palate

What’s an aneurysm?

An aneurysm is a bulge in the wall of a blood vessel. It’s a problem because the wall is weakened where it is stretched (picture a balloon that’s been overinflated); if the blood pressure becomes too high, the aneurysm can rupture, creating a life-threatening emergency.

Questions to ask your doctor

You and your family are key players in your child’s medical care. It’s important that you share your observations and ideas with your child’s health care provider and that you understand your provider’s recommendations.

If your child has been diagnosed with Loeys-Dietz syndrome and you’ve set up an appointment, you probably already have some ideas and questions on your mind. But at the appointment, it can be easy to forget the questions you wanted to ask. It’s often helpful to jot them down ahead of time so that you can leave the appointment feeling like you have the information you need.

 Some of the questions you may want to ask include:

  • What kinds of tests will our child need?
  • What can we do at home to help manage our child's symptoms?
  • What symptoms should we be on the lookout for?
  • What kinds of treatments will our child need?
  • Where can we go for further information? Printed materials? Online resources?

Coping and support

We understand that you may have a lot of questions when your child is diagnosed with Loeys-Dietz syndrome. How will it affect my child long term? What can we do to treat the symptoms? Will any of the symptoms get better without treatment? We’ve provided some answers to those questions in the following pages, but there are also a number of other resources to help you and your family through this difficult time.

  • Boston Children’s Center for Familiesis dedicated to helping families locate the information and resources they need to better understand their child’s particular condition and take part in their care. All patients, families and health professionals are welcome to use the Center’s services at no extra cost. The center is open Monday through Friday from 8 a.m. to 7 p.m., and on Saturdays from 9 a.m. to 1 p.m. Please call 617-355-6279 for more information.
  • The Boston Children’s chaplaincy is a source of spiritual support for parents and family members. Our program includes nearly a dozen clergy members—representing Episcopal, Jewish, Lutheran, Muslim, Roman Catholic, Unitarian and United Church of Christ traditions—who will listen to you, pray with you and help you observe your own faith practices during your child’s treatment.
  • Boston Children’s Behavioral Medicine Clinic helps children who are being treated on an outpatient basis at the hospital — as well as their families — understand and cope with their feelings about:
    • being sick
    • facing uncomfortable procedures
    • handling pain
    • taking medication
    • preparing for surgery
    • changes in friendships and family relationships
    • managing school while dealing with an illness
    • grief and loss
  • Boston Children’s Pediatric Psychiatry Consultation Service is made up of expert and compassionate pediatric psychologists, psychiatrists, social workers and other mental health professionals who understand the unique circumstances of hospitalized children and their families. The service works with children who have been admitted to the hospital—and their family members—and operates on a referral basis.
  • The Experience Journal was designed by Boston Children’s psychiatrist-in-chief David DeMaso, MDand members of his team. This online collection features thoughts, reflections and advice from kids and caregivers about their medical experiences.
  • getting to Boston Children’s
  • accommodations
  • navigating the hospital experience
  • resources that are available for your family

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