A rhabdomyoma is a cardiac tumor (a tumor on or in the heart). This type of tumor is not cancerous and will not spread. Rhabdomyoma is the most common form of heart tumor. 

These tumors can vary greatly in size and number. Rhabdomyomas are usually multiple in number and can affect either side of the heart. In 30% of cases, these tumors occur in both sides of the heart. The fastest growth time for these tumors is between the second and third trimester. Growth slows as the pregnancy nears its end and stops when the baby is born.

Cardiac tumors are rare at any age. They have an estimated occurrence rate of one in 6,000 to one in 10,000. For an unborn baby, the diagnosis of rhabdomyoma accounts for approximately 1% of all cardiac disorders that can be diagnosed prenatally by ultrasound exam. 

Hydrops

The smaller tumors will typically grow in proportion to the baby. A large tumor may grow faster than the baby and can block blood flow to and/or from the heart. This blockage to blood flow can result in heart failure and the development of hydrops.

Hydrops or non-immune hydrops is a condition in which fluid collects in at least two body cavities. The areas where fluid can collect include: 

• The space around the heart and/or lungs
• In the abdomen
• Under the skin
• In the scalp

It also can cause generalized swelling. 

The presence of hydrops usually means a baby is at high risk for a poor outcome. Experts estimate that 50-98% of children with hydrops will not survive. This depends upon the age at which hydrops develops, why it developed and where the fluid has collected. 

Cardiac Arrhythmias

An arrhythmia is an abnormal heart rate. There are different types of arrhythmias. About 20% of babies with rhabdomyomas have this complication. Arrhythmias develop when the tumors are close to an electrical conduction area of the heart. 

Tuberous Sclerosis (TS) 

The biggest concern when a rhabdomyoma is seen on prenatal ultrasound is the link between these tumors and tuberous sclerosis. TS is also called tuberous sclerosis complex (TSC). The name comes from the tubers or root-like growths of the brain that calcify with age and will become hard, or sclerotic. 

Tuberous sclerosis is a neurocutaneous disorder. "Neuro" refers to neurologic issues that have to do with the brain, spine, and peripheral nerves (in the arms and legs). "Cutaneous" refers to the skin. Skin lesions are the most common symptom of this disorder. 

Some studies suggest the link between rhabdomyomas and TS to be as high as 80%. Up to 50% of these cases have a familial occurrence. This means one or both parents may discover they have a very mild form of TS. In some cases, a parent will be diagnosed with tuberous sclerosis after their baby is. 

Tuberous sclerosis is an autosomal dominant condition. Autosomal means both males and females are affected equally. Dominant means that only one parent would need to contribute the gene for TS in order for it to occur. A parent with TS has a 50% chance of having a child with TS. 

For the remaining 50% of patients, TS is caused by a new mutation, and no other cases in the family will be discovered. However, parents of these children still may be at an increased risk for having another child with TS. 

Doctors make a prenatal diagnosis of rhabdomyoma when one or more masses are noted within the heart of the fetus on a prenatal ultrasound. 

If your baby is diagnosed with rhabdomyoma or you have a family history of the condition, you likely will have to have more tests to confirm the diagnosis and to monitor your baby’s development. Some of those tests include:

• Ultrasound: Your doctor may discover these tumors during a routine ultrasound. However, doctors cannot see most of these tumors until after 22 weeks of gestation. If there is a known family history, experts recommend that mothers have serial ultrasounds (done at regular intervals) starting at about 20 to 22 weeks, even if no tumors are found on the first ultrasound exam. The ultrasound technician should pay particular attention to the heart, nervous system and kidneys.
• Fetal echocardiogram: We recommend that you have a fetal echocardiogram (ultrasound of the heart) to examine your baby’s heart. A pediatric cardiologist (heart specialist) will perform this exam. If they see tumors on your baby’s heart, the most likely diagnosis is rhabdomyomas. There usually will be more than one tumor, so determining the number of tumors, their size and location, and their potential to block blood flow and/or heart function is important to help determine the likely outcome. 
  
  Another potential effect of these tumors is arrhythmias (irregular heartbeat or a heart rate that is either too fast or too slow) and interference with the cardiac conduction system. Watching for fetal arrhythmias also is important to help predict the likely outcome for your baby.
• Exam of the fetal anatomy: Doctors should perform a thorough exam of your baby to look for other birth defects. Cysts (fluid-filled tumors) within the kidneys and disorders of the brain are some of the more common findings that may accompany TS.

The effects of rhabdomyoma(s) depend on their location, number and size. If there is no issue with blocked blood flow or cardiac arrhythmias, newborns with rhabdomyomas are usually born without any symptoms of TS at birth. 

Tuberous sclerosis is characterized by tubers that grow in various parts of the body and can affect any organ. Organs that are often affected are: 

• Brain
• Lungs
• Heart
• Kidneys
• Skin
• Bone
• Eyes

These tubers can have a wide range in effects, which can vary from person to person within the same family. Experts do not yet understand why some people are severely affected while others seem to have very mild symptoms. Neurologic and skin problems are the most common symptoms and occur in up to 90-95% of TS cases.

Some of the symptoms and effects of TS include:

• Neurologic consequences of TS are the result of tubers growing in the brain. The location, size and number of tubers are significant to outcome. The brain can be affected in different ways, depending on the location of the tubers. Neurologic symptoms can include: 
   
  • Seizures
  • Hydrocephalus
  • Developmental delays
  • Language delays
  • Motor delays
  • Gait abnormalities
• Mental disabilities occur in 1/2 to 2/3 of those affected by TS. These can range from mild learning disabilities to severe developmental delays.
• Skin findings of TS include some specific skin disorders that cause your doctor to suspect TS if it has not already been diagnosed. 
   
  • Angiofibromas are flat, reddish lesions that may be mistaken for freckles initially. They become redder with time and may bleed easily. These types of lesions may first be noticed when the child is young, but will typically become larger during puberty.
  • Other lesions may appear as white spots. These may be referred to as ash leaf spots and may appear anywhere on the body.
  • Shagreen patch is a thickened area of tissue found on the lower back or the nape of the neck.
  • Skin tags across the back of the neck and shoulders are another common skin condition.
• Kidney problems occur in 40-80% of people with TS. Cysts (fluid-filled tumors) and noncancerous growths will commonly occur between the ages of 20 and 30.
• Behavioral issues can occur at any age in people with TS. These can include: 
   
  • Aggression
  • Sudden rage
  • Attention deficit hyperactivity disorder (ADHD)
  • Acting out
  • Obsessive-compulsive disorder (OCD)
  • Repetitive, destructive or self-harming behavior

Some people with TS have autism, which is a developmental disorder. 

If your doctor diagnosed your baby with tumors in the heart that are likely rhabdomyomas, you should deliver them at a tertiary care center where doctors and staff can care for both you and your baby after delivery. 

The tertiary care center will have specialists on staff that can provide the care your baby may need. Those specialists include:

• A neonatologist: A neonatologist is a doctor who specializes in caring for sick newborns. Because your baby will have an increased risk of heart arrhythmias, a neonatologist should be present at the delivery.
• A pediatric cardiologist: This doctor will examine your baby’s heart by performing an echocardiogram after birth and treating an arrhythmia if it develops. 

Your baby also will have to have tests which may include:

• An electrocardiography (EKG/ECG) to look at the heart rhythm.
• MRI to look for tuberous growths, especially in the brain.

If your baby does not have heart failure and/or an arrhythmia related to the cardiac tumors, they will typically have a short hospital stay and will be followed on an outpatient basis. 

Many babies with rhabdomyomas will not stay in the hospital long after delivery. Your baby’s doctors will perform tests to determine how well their heart is working and to follow the growth and shrinking of the rhabdomyomas. 

Doctors also may recommend other tests to look for other tumors or growths in the body. However, you can schedule these tests on an outpatient basis after your baby leaves the hospital if there are no concerns or symptoms at the time of birth. 

Long-term prognosis for infants who are born full-term and do not develop non-immune hydrops is reasonably good. 

There are concerns of long-term effects with the diagnosis of tuberous sclerosis. Developmental outcomes for infants known to have TS vary widely, from normal intelligence to severe developmental delays. 

Experts estimate that 38% of children with TS have developmental delays. Those who develop seizures within the first year of life are at an increased risk for mental disabilities. Other health effects of TS include: 

• Renal tumors
• Lung tumors
• Seizure disorders
• Skin growths of various types

When there is a known family history of TS, the occurrence in future generations varies as well. This means a parent of normal intelligence, who is diagnosed with TS based on the findings of a fetal ultrasound, can have a child who is severely affected. 

Two genes (TSC1 and TSC2) have been identified as causing TS. Approximately 66% with TS have the gene change as the result of a sporadic event, meaning no other family members have TS. Approximately 33% with TS inherit the gene change from one of their parents. Each individual with TS has a 50% chance to pass the gene change on to each of their children. In rare cases (1-2%), an unaffected parent may have more than one child with TS due to gonadal mosaicism. In cases of gonadal mosaicism, a parent only has the gene change for TS present in some of their egg or sperm cells. The rest of the cells in the parent’s body do not have the gene change for TS and the parent does not have features of TS. For this reason, some families have recurrent cases of children affected with TS even though neither parent is affected.