What is a rhabdomyoma? What is tuberous sclerosis?
A rhabdomyoma is the most common form of cardiac tumor. It is not malignant (cancerous) and will not spread (metastasize). Cardiac tumors are rare at any age. They have an estimated occurance rate of 1:6,000 to 1:10,000. For a fetus (unborn baby) the diagnosis of rhabdomyoma accounts for approximately 1 percent of all cardiac disorders that can be seen prenatally by ultrasound exam. 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 percent of cases these tumors have been found 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.
The smaller tumors will typically grow in proportion to the fetus. A large tumor may grow faster than the fetus 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 and/or generalized swelling. The presence of hydrops usually means the baby is at high risk for a poor outcome. It is estimated that 50 to 98 percent will not survive. This is dependent on the age at which hydrops develops, why it developed and where the fluid has collected. Arrythmias (abnormal heart rate) are another issue seen in about 20 percent of patients with these tumors. Arrythmias develop when the tumors are close to an electrical conduction area of the heart.
The biggest concern when a rhabdomyoma is seen on prenatal ultrasound is the link between these tumors and tuberous sclerosis (TS; also called tuberous sclerosis complex or 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 classified as 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 percent. Up to 50 percent of these will be discovered to have a familial occurence. 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 fetus is. Tuberous sclerosis is an autosomal dominant condition. Autosomal means that both males and females will be 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 50/50 chance of having a child with TS.
For the remaining 50 percent of patients, TS will be caused by a new mutation and no other cases in the family will be discovered. However, these parents still may be at an increased risk for having another child with TS.
Prenatal diagnosis of rhabdomyoma:
The prenatal diagnosis of rhabdomyoma is made when one or more masses are noted within the heart of the fetus on a prenatal ultrasound. This discovery may be with a routine ultrasound by your obstetrician. However, most of these tumors are not seen until after 22 weeks' gestation. If there is a known family history it is recommended that even though the initial ultrasound exam may be within normal limits and no tumors are noted, serial ultrasound exams (done at regular intervals, for example every four weeks) should be performed starting at about 20 to 22 weeks. Particular attention should be paid to the heart, nervous system and kidneys.
Fetal echocardiogram (ultrasound of the heart) is recommended to examine the heart. This ultrasound exam is performed by a pediatric cardiologist. When tumors are seen, the most likely diagnosis is rhabdomyomas. There typically will be more than one tumor, so determining how many, their size and location, along with their potential to block blood flow and/or cardiac function is important to note to help determine the likely outcome. Another potential affect of these tumors is interference with the cardiac conduction system and arrhythmias (irregular heartbeat or a heart rate that is either too fast or too slow). Watching for fetal arrythmias is also important to help predict the most likely outcome for the baby.
A thorough exam of the fetal anatomy (body and all its systems) should be done 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 be seen with TS. Your obstetrician will likely refer you to a specialist that handles high-risk pregnancies. These doctors are called perinatologists.
Another specialist you will meet with is a geneticist. A detailed history of at least three generations will be obtained. The geneticist may also recommend blood work to examine for known gene mutations associated with TS (to determine if one of the parents may have TS).
This diagnosis is unlikely to have any effect on the pregnancy. An amniocentesis may be recommended to examine the fetus for the genes to diagnose TS. The risks and benefits of this procedure will be discussed with you by the perinatologist prior to the procedure being performed.
If the baby develops non-immune hydrops, there is an increased risk for the mother to develop symptoms similar to the fetus. This is called "mirror syndrome." Mirror syndrome requires hospitalization and careful observation of the mother. You will be monitored closely for development of this complication. The treatment for "mirror syndrome" is delivery of the baby.
How does rhabdomyoma/tuberous sclerosis affect my baby?
The affects of rhabdomyoma(s) depend on their location, number and size. If there is no issue with blocked blood flow or arrythmias (changes in the heart rate or pattern) these newborns are usually born without any symptoms of TS at birth.
Tuberous sclerosis is characterized by tubers (root-like growths) that grow in various parts of the body and can affect any organ, including the brain, lungs, heart, kidneys, skin, bone, and eyes. These tubers can have a wide range in effects, which can vary from person to person within the same family. It is not yet understood why some people are severely affected while others seem to have very mild symptoms. Neurologic and skin problems are the most common symptoms and are found in up to 90 to 95 percent of TS cases.
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 and gait abnormalities.
Mental disabilities can be seen in one-half to two-thirds 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 physician to suspect TS if not already diagnosed.
- Angiofibromas are flat, reddish lesions that may be mistaken for freckles initially. They become more red and may bleed easily. These type 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 at the lower back or nape of the neck.
- Skin tags across the back of the neck and shoulders are another common skin condition.
Kidney problems also are seen in 40 to 80 percent of people with TS. Cysts (fluid-filled tumors) and benign (not cancerous) 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, acting out, obsessive-compulsive disorder and repetitive, destructive or self-harming behavior. Some people with TS have autism, which is a developmental disorder.
How does rhabdomyoma/tuberous sclerosis affect my pregnancy?
The diagnosis of rhabdomyomas in the fetus will typically have no affect on the pregnancy except that the baby requires closer observation for growth of the tumors. If the tumors grow out of proportion to fetal growth they could alter cardiac function. If the fetus develops cardiac failure and non-immune hydrops, the mother is at an increased risk for developing problems as well. The mother can develop mirror syndrome which causes symptoms in the mother that mimic the symptoms of the fetus. This is a serious complication that requires close observation. The treatment for mirror syndrome is delivery of the baby.
The other issue for the mother of a fetus with rhabdomyomas is to search the family genetic history for others affected by tuberous sclerosis. Genetic counseling and potentially genetic testing may be recommended to determine if one parent has a mild case. Other testing to make a diagnosis of TS can include a skin exam, computed tomography scan, magnetic resonance imaging of the brain, and renal ultrasound. Each of these tests can locate tuberous growths or skin issues commonly seen with TS.
How is rhabdomyoma/tuberous sclerosis treated?
A fetus who has been prenatally diagnosed with tumors in the heart which are suspected to be rhabdomyomas should be delivered at a tertiary care center. A neonatologist should be present at the delivery due to the risk of an arrhythmia. A pediatric cardiologist also should be available to examine the heart structure by performing an echocardiogram test after birth and to treat any arrhythmia that should develop. An electrocardiography (EKG/ECG) may be recommended to look at the heart rhythm. Magnetic resonance imaging is recommended to look for tuberous growths, especially in the brain. If an infant does not have heart failure and/or an arrhythmia related to the cardiac tumors, he or she will typically have a short hospital stay and will be followed on an outpatient basis. These cardiac tumors typically are not surgically removed, as they will shrink in size as the infant grows.
The symptom that causes the most concern in an infant is seizures. This symptom can lead to a poorer long-term outcome with increased likelihood of more severe developmental delays.
Children with tuberous sclerosis may be followed by a variety of subspecialists. Those most commonly involved in the care of patients with TS include cardiology, neurology, urology or nephrology and dermatology.
When can my baby go home?
Many of these babies will not stay in the hospital long after delivery. Tests will be done to determine the cardiac function and to follow the growth and shrinking of the rhabdomyomas. Other tests may be done to look for other tumors or growths in the body. However, these tests may be done after discharge, on an outpatient basis, if there are no concerns or symptoms at the time of birth.
What is my baby's long-term prognosis?
Long-term prognosis for infants who are born full term and do not develop non-immune hydrops are 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. It is estimated that 38 percent of TS patients 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 and skin growths of various types.
When there is a known family history of TS, the occurence 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.
Several genes have been identified as causing TS, and are used to diagnose this disorder. It is now suspected that as many as 10 percent may have a gonadal mosaicism. This means that the parent has a mutation of a gene in one of the sex-linked chromosomes (x and y chromosomes). The parent will present without TS and when genetic testing is performed the typical genes associated with TS will not be evident. Only the sex-linked cells are involved and only some of them have the mutation while others will be normal. For this reason, some families have recurrent cases of children affected with TS even though neither parent is affected.