Sirenomelia is a malformation of the lower half of the fetus‘ body, beginning with the pelvic area and ending with 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 a deformity of the legs and feet. These are, depending on the severity of the sirenomelia, only rudimentarily present as well as fused together. The fusion extends not only to the soft tissues but also to the bones, as far as they have been formed at all. The resulting conical shape of the lower body is reminiscent of the fish tails of sirens. These, a mermaid resembling figures from Greek mythology, were thus also the basis for the naming of the Sirenomelie. In earlier times, people even spoke directly of a sirenomelia. The occurrence of sirenomelia is very rare and happens exclusively sporadically. A little more than 450 cases are known worldwide so far. The probability of a disease is 1:100,000. Currently there are two people living with sirenomelia. They are two girls from the United States and Peru. However, according to studies, there is basically a slight excess of male sufferers.
Causes
Despite intensive research, the cause of sirenomelia is still unknown. Over the years, various theories have been voiced. None provided conclusive evidence to date. In the early days of sirenomelia research, internal and external mechanical influences, such as pressure exerted on the amniotic fold, were suspected. Later, disorders in embryonic development were under discussion. Theories included, for example, a developmental disorder of the cloaca, aplasia or dysplasia of the pelvis and sacrum, or hyperextension of the neural tube. In the meantime, an interaction of several factors is discussed. However, a genetic cause seems most likely at present. However, an existing sirenomelia gene has already been ruled out. In order to clarify the triggering cause, several animal experiments were also carried out. Methods based on genetics and teratogenic substances such as cadmium and lead were used. Surprisingly, sirenomelia could be induced by these methods. The changes in the animals were very similar to those in humans. However, a clear explanation for the development of sirenomelia also remained elusive.
Symptoms, complaints, and signs
Sirenomelia develops in the womb. Indications as to whether or when the adhesions and deformities of the lower half of the body are already detectable by ultrasound could not be found. In any case, evaluations concerning the mothers are very limited. However, there is talk about insufficient amount of amniotic fluid, changes in the placenta and changes in the umbilical cord. Almost two thirds of fetuses suffering from sirenomelia are stillborn. The remaining children are mostly born prematurely and are subsequently barely viable. They die within a few hours or days. In addition, further malformations frequently occur. Not infrequently, renal agenesis, Potter-face, vertebral anomalies, scoliosis, pulmonary hypoplasia, multiple cardiac and vascular anomalies, and anorectal atresia have been observed simultaneously. Furthermore, the external sex organs are largely absent and only a single umbilical artery is present.
Diagnosis and Course of the Disease
Diagnosis occurs at the latest after birth. A specialist examination determines whether sirenomelia, a deformity of both extremities and a definite adhesion, is actually present. If this is not the case, one speaks only of sirenoid malformations or pseudosirenia. Incidentally, humans are the only mammals in which sirenomelia occurs spontaneously.
Complications
In sirenomelia, the unborn child suffers from severe malformations. The symptoms can usually be diagnosed before birth. In this case, especially the parents and the relatives of the child suffer from psychological discomfort or even depression. As a rule, sirenomelia leads to the death of the affected person and thus to stillbirth. If the child is born alive, it often dies from the malformations a few days after birth. The children suffer from malformations of the internal organs and also from malformations of the face.The heart is also strongly affected by the malformations. Furthermore, in most cases, the child’s sexual organs are also absent or only very slightly developed. In most cases, the treatment of sirenomelia depends on the psychological discomfort of the parents and relatives. The life of the child cannot be saved in this case. The parents are dependent on psychological treatment. In most cases, complications can be avoided in this case with the help of early treatment.
When should you go to the doctor?
In the case of sirenmelia, treatment by a doctor is necessary and advisable in any case. Since this disease is hereditary, there is also no possibility of self-cure. In order to prevent inheriting the disease to the descendants, genetic counseling should be performed if the patient wishes to have children. A doctor should be consulted in case of sirenomelia if there are severe malformations or deformities on the child’s body. In most cases, these conditions can be detected by ultrasound examination before birth, eliminating the need for subsequent diagnosis. In most cases, the child also dies after birth, so that no further treatment takes place. Since sirenomelia can cause severe psychological discomfort or upset and depression in parents and relatives, psychological treatment should also be sought. In many cases, contact with other affected parents of sirenomelia is also useful and can relieve discomfort.
Treatment and therapy
Treatment of sirenomelia per se is not possible. If a child survives birth, further survival depends on the type and severity of other existing malformations. Most important is the functionality of the internal organs. That life is possible with a mild form of sirenomelia is shown by the cases already mentioned in the USA and Peru. 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 it again and precisely defined the present subspecies.
- The lightest 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 sirenomelia ends with only one foot, it is Sympus monopus, the moderately severe form of sirenomelia. The existing foot usually points backward.
- In the most severe form, Sympus apus, the thighs are fused together. The rest of the legs are deformed and bend forward. Feet are also completely absent at the base.
Basically, to a greater or lesser extent, the pelvis and lumbar spine are also affected in all three subspecies. Especially in the pelvis, the deformities often occur unilaterally, resulting in an asymmetrical shape.
Prevention
According to current knowledge, there are no possibilities for prevention. If a severe form of sirenomelia is diagnosed in time, the only reasonable option appears to be abortion. It can be assumed that, despite the small number of cases, further research on sirenomelia will be conducted. The main focus could be on twin research. The probability of a twin birth and sirenomelia occurring simultaneously is significantly increased. For the most part, however, only one twin is affected at a time.
Follow-up
Follow-up care for sirenomelia includes regular physical examinations and discussions with physicians and therapists. The measures that are useful in detail depend on the form of sirenomelia. In the case of sympus dipus, the mildest form of sirenomelia, physiotherapeutic measures can be part of the aftercare. Patients mostly need to take pain medication, blood thinners and other drugs. The intake of the preparations must be monitored by a physician. Medication must be readjusted at regular intervals. After corrective surgical procedures, the patient must spend a few days in the hospital. In Sympus monopus, the moderately severe form, permanent follow-up is indicated. Patients require support in everyday life, as independent movement is not possible due to the severe deformities.In Sympus monopus, medication and physiotherapy are also part of the aftercare. As a rule, 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. Follow-up care is usually limited to psychological support for the relatives. Follow-up care for sirenomelia is provided by general practitioners, orthopedists, and, depending on the symptoms, other specialists.
What you can do yourself
About 70 percent of children who have sirenomelia die while still in their mother’s womb. Another large percentage die immediately after birth or in the first few days and weeks. Parents must deal with the thought that the child may die at an early stage. If necessary, a therapist should also be called in to provide grief counseling for the parents. Which measures make sense in detail depends on the individual course of the disease. The parents of a sick child are best advised 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 specialized clinic. Parents should contact the appropriate doctors at an early stage. Should the condition take a positive course, the necessary measures must be taken to enable the child to live as symptom-free a life as possible. In addition to early acquisition of aids such as wheelchairs and crutches, this also includes contacting the health insurance company so that costs can be covered.
