By | June 10, 2022

Sirenomelia is a malformation of the lower half of the fetus’ body, beginning with the pelvis and ending in the feet. It is also called symmelia, sympodia or simply mermaid syndrome. The ICD-10 classification is Q47.8.

What is sirenomelia?

Sirenomelia is characterized by deformity of the legs and feet. Depending on the severity of the sirenomelia, these are only rudimentarily present and have grown together. The fusion extends not only to the soft parts but also to the bones, insofar as such have formed at all. For what does bronchial asthma mean, please visit

The resulting conical shape of the lower body is reminiscent of the fishtails of sirens. These figures from Greek mythology, which resemble a mermaid, were therefore also the basis for the naming of Sirenomelia. In the past, there was even direct talk of a siren deformity.

The occurrence of a sirenomelia is very rare and only happens sporadically. A little more than 450 cases are known worldwide so far. The probability of illness is 1:100,000. There are currently two people living with sirenomelia. They are two girls from the United States and Peru. According to studies, however, there is basically a small excess of male patients.


Despite intensive research, the cause of sirenomelia is still unknown. Various theories have been put forward over the years. So far, no clear evidence has been provided. In the early days of sirenomelia research, internal and external mechanical influences, such as pressure exerted on the amniotic fold, were suspected. Disorders in embryonic development were discussed later.

Theories have included developmental abnormality of the cloaca, aplasia or dysplasia of the pelvis and sacrum, or overstretching of the neural tube. In the meantime, the interaction of several factors is being discussed. However, a genetic cause seems most likely at the moment. However, an existing sirenomelia gene has already been ruled out.

In order to clarify the triggering cause, some animal experiments were also carried out. Methods based on genetics and using teratogenic substances such as cadmium and lead have been used. Amazingly, sirenomelia could be induced using these methods. The changes in animals were very similar to those in humans. However, there was also no clear explanation for the emergence of sirenomelia.

Symptoms, Ailments & Signs

Sirenomelia develops in the womb. It was not possible to find any indications as to whether or when the adhesions and deformities of the lower half of the body can be detected using ultrasound. In any case, evaluations of the mothers are very limited.

However, there is talk of an insufficient amount of amniotic fluid, a change in the placenta and changes in the umbilical cord.

Almost two-thirds of fetuses with sirenomelia are stillborn. Most of the remaining children are born prematurely and are then hardly viable. They die within hours or days.

Other malformations often occur as well. Renal agenesis, Potter face, vertebral anomalies, scoliosis, pulmonary hypoplasia, multiple cardiac and vascular anomalies and anorectal atresia were often observed at the same time. Furthermore, the external sex organs are largely non-existent and only a single umbilical artery is present.

Diagnosis & course of disease

The diagnosis is made after birth at the latest. A specialist examination determines whether there is actually sirenomelia, i.e. a deformation of both extremities and a clear adhesion. If this is not the case, one only speaks of sirenoid malformations or pseudo sirens. Incidentally, humans are the only mammal in which sirenomelia occurs spontaneously.


In the case of sirenomelia, the unborn child suffers from severe malformations. The symptoms can usually be diagnosed before birth. The parents and relatives of the child in particular suffer from psychological problems or depression. As a rule, sirenomelia leads to the death of the affected person and thus to a stillbirth.

If the child is born alive, it often dies a few days after birth from the malformations. The children suffer from malformations of the internal organs and also from malformations of the face. The heart is also severely affected by the deformities. Furthermore, in most cases the genital organs of the child are absent or only very slightly developed.

In most cases, the treatment of sirenomelia depends on the psychological symptoms of the parents and relatives. The life of the child can no longer be saved. The parents need psychological treatment. In most cases, complications can be avoided with early treatment.

When should you go to the doctor?

In the case of a siren melia, treatment by a doctor is necessary and sensible in any case. Since this disease is a hereditary disease, it cannot heal itself. In order to prevent the disease from being passed on to descendants, genetic counseling should be carried out if you wish to have children. A doctor should be consulted for sirenomelia if severe malformations or malformations occur on the child’s body.

In most cases, these symptoms can be detected before birth by means of an ultrasound examination, so that a subsequent diagnosis is no longer necessary. In most cases, the child also dies after birth, so that no further treatment takes place. Since sirenomelia can lead to severe psychological problems or to moodiness and depression in parents and relatives, psychological treatment should also be sought. In many cases, contact with other affected parents of sirenomelia is useful and can alleviate symptoms.

Treatment & Therapy

Sirenomelia itself cannot be treated. If a child survives the birth, further survival depends on the type and severity of other malformations present. The functionality of the internal organs is particularly important. The cases in the USA and Peru already mentioned show that life with a mild form of sirenomelia is possible.

Sirenomelia is classified into three degrees of severity. Geoffroy Saint-Hilaire first made this classification in the 19th century and spoke of Symméle, Uroméle and Sirénoméle. The Würzburg pathologist August Förster revised them again and exactly defined today’s subspecies.

  • The mildest form of sirenomelia is called sympus dipus. In this species, the legs are completely fused together. In addition, two feet are clearly recognizable or present.
  • If the typical conical siren abdomen ends with only one foot, it is Sympus monopus, the moderate form of sirenomelia. The existing foot usually points backwards.
  • In the most severe form, sympus apus, the femurs are fused together. The remaining legs are deformed and bend forward. Feet are also completely missing.

In principle, the pelvis and the lumbar spine are also affected to a greater or lesser extent in all three subspecies. Especially in the pelvis, the deformations often occur on one side, resulting in an asymmetrical shape.


According to the current state of knowledge, there are no possibilities for prevention. If a severe form of sirenomelia is diagnosed in good time, the only sensible option is an abortion. It can be assumed that, despite the small number of cases, further research into sirenomelia will be carried out.

The main focus could be placed on twin research. The likelihood of twin birth and sirenomelia occurring at the same time is significantly increased. In most cases, however, only one twin is affected.


Follow-up care for sirenomelia includes regular physical exams and consultations with doctors and therapists. The detailed measures that make sense depend on the form of the sirenomelia. In the case of sympus dipus, the mildest form of sirenomelia, physiotherapeutic measures can be part of the aftercare. Patients usually have to take pain medication, blood thinners and other drugs.

The intake of the preparations must be monitored by a doctor. The medication must be adjusted at regular intervals. After corrective surgical interventions, the patient has to spend a few days in the hospital. In the case of Sympus monopus, the moderate form, long-term follow-up care is indicated. The patients need support in everyday life, as independent movement is not possible due to the severe malformations.

Medication and physiotherapy are also part of the aftercare for Sympus monopus. Usually, patients and their relatives also receive psychological support. In sympus apus, the most severe form, the life expectancy of patients is significantly reduced.

Most patients die before or shortly after birth. Aftercare is usually limited to psychological care for the relatives. Follow-up care for sirenomelia is provided by general practitioners, orthopedists and, depending on the symptoms, other specialists.

You can do that yourself

Around 70 percent of children suffering from sirenomelia die in their mother’s womb. Another majority dies immediately after birth or in the first few days and weeks. The parents have to deal with the thought at an early stage that the child may die. If necessary, a therapist should also be consulted for this purpose, who will take over the grief counseling of the parents. Which measures make sense in detail depends on the individual course of the disease.

It is best for the parents of a sick child to talk to their family doctor or a therapist about further measures. Since sirenomelia is an extremely rare disease, the exact measures must be determined in a specialist clinic. Parents should contact the appropriate doctors at an early stage.

If the condition takes a positive course, the necessary measures must be taken to enable the child to lead a life as free of symptoms as possible. In addition to the early purchase of aids such as wheelchairs and crutches, this also includes contacting the health insurance company so that the costs can be covered.