Sirenomelia, also called mermaid syndrome, is a rare congenital deformity in which the legs are fused together, giving the appearance of a mermaids tail, hence the nickname. Classification
Sirenomelia is classified by the skeletal structure of the lower limb, ranging from class I, where all bones are present and only the soft tissues are fused, to class VII where the only bone present is a fused femur.It has also been classified as an expanded part of the VACTERL association and as a form of caudal regression syndrome. Presentation
Sirenomelia is mainly characterized by the fusion of both legs with rotation of the fibula. It may include the absence of the lower spine, as well as abnormalities of the pelvis and renal organs. It was previously thought to be a severe form of sacral agensis/caudal regression syndrome, but more recent research confirms that these two conditions are not related. NORD has a separate report on caudal regression syndrome. In general, the more severe cases of limb fusion correlate with more severe dysplasia in the pelvis. Rather than the two iliac arteries present in fetuses with complete renal agenesis, fetuses with sirenomelia display no branching of the abdominal aorta, which is always absent.Associated defects recorded in cases of sirenomelia include neural tube defects (rachischisis, anencephaly, and spina bifida), holoprosencephaly, hypoplastic left heart syndrome, other heart defects, esophageal atresia, omphalocele, intestinal malrotation, persistent cloaca, and other limb defects (most commonly absence of the radius). Causes
The ultimate cause of sirenomelia is a subject of debate.
One-third to one-half of infants are stillborn, with all but a few dying in the neonatal period.In cases of monoamniotic twins where one is affected, the twin with sirenomelia is protected from Potter sequence (particularly pulmonary hypoplasia and abnormal facies) by the normal twins production of amniotic fluid. Epidemiology
This condition is found in approximately one out of every 100,000 live births; studies produce rates from 1 in 68,741 to 1 in 97,807. It is 100 to 150 times more likely in identical (monozygotic) twins than in singletons or fraternal twins. Sirenomelia is not associated with any ethnic background, but fetuses with sirenomelia are more likely to be male. Etymology
The word sirenomelia derives from the ancient Greek word seirēn, referring to the mythological Sirens, who were sometimes depicted as mermaids, and melos, meaning "limb". History
Sirenomelia was first reported in 1542. In 1927, Otto Kampmeier discovered the association between sirenomelia and single umbilical artery. Notable individuals
Only a few individuals who had some functioning kidney tissue have survived the neonatal period. Tiffany Yorks
Tiffany Yorks of Clearwater, Florida (May 7, 1988 – February 24, 2016) underwent successful surgery in order to separate her legs before she was a year old. She was the longest-surviving sirenomelia patient to date. She had mobility issues due to her fragile leg bones, and compensated by using crutches or a wheelchair. She died on February 24, 2016, at the age of 27.