Sirenomelia: Causes, Symptoms, Risk Factors, Treatment

WhetherParentsEver heard of a rare disease called mermaid syndrome? Mermaid syndrome or often referred to as sirenomelia causes babies to be born with legs that are fused from the thigh to the heel, like a mermaid.

That’s why it’s calledmermaid syndrome . Babies who experience mermaid syndrome also generally do not have a tailbone and sacrum. To learn about this rare syndrome, let’s look at the following review of sirenomelia.

Definition of Mermaid Syndrome or Sirenomelia

Image source: Journal of Medical Case Reports

Sirenomelia also known as mermaid syndrome is a very rare congenital developmental disorder characterized by anomalies of the lower spine and lower limbs. 

Sirenomelia is a severe form of caudal regression syndrome , a term for disorders involving problems with the formation of the lower part of the spine. 

However, recently many researchers have indicated that sirenomelia is a similar, but distinct, disorder to caudal regression syndrome . NORD (National Organization for Rare Disorders ) has a separate report on caudal regression syndrome .

Symptoms of Sirenomelia

There are a variety of physical malformations that can potentially occur with sirenomelia. Specific findings can vary greatly from one individual to another. 

Sirenomelia is associated with severe life-threatening complications and is often fatal in the first years of life. 

According to the Rare Disease and Healthline pages , babies born with mermaid syndrome also tend to have other abnormalities that affect their ability to survive outside the womb, including:

• Affected babies may have only one femur (the long bone of the thigh) or have two femurs in one shell. 
• The tailbone is absent.
• They may have imperforate anus, a condition in which the thin lining that blocks the anal opening or the canal that normally connects the anus and the lower part of the large intestine (rectum) fails to develop.
• Having only one leg, and no legs or both legs cannot be rotated so that the back of the leg faces forward.
• The lowest part of the large intestine, also known as the rectum, fails to develop.
• Having a congenital heart defect .
• Partially or completely missing sacrum, which is a triangular or curved bone formed by 5 fused vertebrae.
• In some patients, an abnormal curvature of the spine ( lordosis ) may occur. 
• Spina bifida is a birth defect that occurs due to disruption of the formation of the neural tube while the baby is in the womb.
• Having various urogenital abnormalities, such as only one kidney, cystic kidney abnormalities, absent bladder, and narrowing of the urethra.
• Underdeveloped lungs
• Some individuals with sirenomelia may havemeningomyelocele, a condition in which the membranes covering the spine and, in some cases, the spinal cord itself protrude through a defect in the spine. 

The severity of mermaid syndrome affecting a baby can vary. Once doctors identify that a baby has mermaid syndrome, they will often do further testing to determine if other genetic abnormalities are present.

Causes of Sirenomelia

The exact cause of sirenomelia is unknown. Researchers believe that environmental and genetic factors may play a role in the development of the disorder, during pregnancy.

Most cases arise randomly for no apparent reason (sporadic), suggesting environmental factors or new mutations. 

Researchers believe that environmental or genetic factors have a teratogenic effect on a developing fetus. A teratogen is any substance that can interfere with the development of an embryo or fetus.

Researchers have also linked differences in a specific gene called VAGL1 to an increased risk of mermaid syndrome. However, doctors don’t know exactly why mutations in this gene cause caudal regression syndrome, according to Rare Disease .

According to the Healthline page , some potential environmental causes of mermaid syndrome and other types of caudal regression syndrome include:

• Drinking alcohol during pregnancy
• Amino acid imbalance during pregnancy
• Lack of oxygen in the uterus
• Exposure to toxins, including those in cigarettes, lithium, and cocaine
• Retinoic acid exposure

Most likely, sirenomelia is multifactorial, meaning that several different factors may play a role in causing this disorder.

In addition, different genetic factors may cause the disorder in different people (genetic heterogeneity). Some individuals may have a genetic predisposition to developing the disorder. 

Frequency of Occurrence

A person who is genetically predisposed to becomecarrieror a carrier of a gene for a disease or disorder, but the gene may not be expressed unless it is triggered or “switched on” under certain circumstances, such as by certain environmental factors. 

Quoting the Rare Disease page , sirenomelia affects males more often than females, with a ratio of 2.7:1. The exact incidence is unknown, but sirenomelia is estimated to occur in around 1 in 60,000 to 100,000 births. 

Sirenomelia occurs with greater frequency in one twin of identical (monozygotic) twins, than in fraternal (dizygotic) twins or individuals.

Risk Factors

Doctors do not know exactly what causes mermaid syndrome. However, maternal diabetes has been identified as a risk factor. 

According to Healthline , an estimated 22 percent of fetuses with mermaid syndrome are born to mothers with diabetes. Unfortunately, doctors do not know why diabetes increases the risk of having a baby with mermaid syndrome.

Pregnant women over the age of 40 or younger than the age of 20 are also more likely to have a baby with mermaid syndrome, according to the NCBI website .

Diagnosis

Diagnosis of sirenomelia can be made prenatally, most often during the second trimester, with fetal ultrasound. 

Doctors will usually diagnose mermaid syndrome during pregnancy. Doctors and healthcare providers may perform an ultrasound to look at the fetus. 

At that time, doctors were able to identify abnormalities associated with mermaid syndrome, particularly fused lower limbs.

Journal articles have reported that doctors can diagnose mermaid syndrome as early as the first 13 weeks of fetal development, according to the NCBI website .

Once doctors identify all the abnormalities that occur along with mermaid syndrome, they will talk to parents about treatment options, if any.

Handling

Treatment may require a coordinated effort from a team of specialists. Pediatricians, surgeons, cardiologists, orthopedists, orthopedic surgeons, kidney specialists (nephrologists) and other health care professionals may need to systematically and comprehensively care for a child affected by this disorder.

Surgery has reportedly been successful in separating the fused legs. In preparation for the surgery, a balloon-like tissue expander is inserted under the skin.  When filled with saline solution for a period of time, the balloon expands causing the skin to stretch and grow. 

This excess skin is then used to cover the legs after they are separated. Sirenomelia is usually fatal in the newborn period even with treatment. The leg bones of children with mermaid syndrome who survive this period are often brittle and break easily. 

They may require multiple surgeries, both for their lower body and for other genetic abnormalities, such as kidney problems.

Possible Complications

The birth defect sirenomelia will affect the function of other organ systems, such as the kidneys and urinary tract. Congenital heart defects and respiratory complications such as severe underdevelopment of the lungs (pulmonary hypoplasia) can also be associated with sirenomelia.

Prevention

Because doctors don’t know exactly what causes mermaid syndrome, there’s no surefire way to prevent the condition. 

The doctor will provide information related to maintaining stable blood sugar levels, especially in the first trimester of pregnancy. Hopefully, it can help prevent mermaid syndrome from occurring.

Mermaid syndrome is a severe and often fatal birth defect. Doctors emphasize regular prenatal care to improve diagnosis and detection.

***

If you are concerned about this condition, your doctor can talk to you about medications and substances that can cause birth defects, including mermaid syndrome. Ideally, this can help prevent birth defects where possible.

That is the information we can get from sirenomelia which has another name mermaid syndrome. Hopefully useful.

Republished with permission from theAsianParent Indonesia