Edwards’ syndrome, also called trisomy 18, is a rare chromosome abnormality, similar to the Patau syndrome, caused by an extra copy of segments or the entire chromosome 18 in the cells.
Just as with the Patau syndrome, there are three different types of trisomy 18. In the first type, an extra copy of the entire chromosome is present in every cell of the body. The second type is mosaicism: the third copy of the chromosome occurs only in some cells of the body. The third type is partial trisomy: in this case only some segments of chromosome 18 are present in three copies, not the entire chromosome. In rare cases, the extra chromosome or segment is attached to another chromosome (called translocation in the literature).
The normal development of the fetus is disturbed by the amount of extra DNA. The severity of the symptoms depends on the place on chromosome 18 where the changes occurred (partial trisomy). In the case of mosaicism, severity is determined by the percentage proportion of cells in which this abnormality occurs.
How common is Edwards’ syndrome?
This condition is rarer than Down syndrome, but more frequent than Patau syndrome. According to international literature data, Down syndrome occurs in 1 in 700 newborns on the average, while the average incidence of Patau syndrome is 1 in 10,000 newborns. Edwards’ syndrome occurs in 1 in 3,000 pregnancies and 1 in 6,000 live newborns on the average. Approximately 50% of the babies diagnosed with Edwards’ syndrome at gestational age die in the womb. A further 50% of the newborns have a chance to stay alive for more than a week. Some of them reach even puberty, but severe health and developmental problems.
There is a significant difference in incidence between genders: this condition affects three times more girls than boys.
What are the symptoms of Edwards’ syndrome?
Many of the newborns with Edwards’ syndrome show grow impairment, and feeding and breathing problems. The newborns develop slower than normal, and mental retardation may occur. Cryptorchidism is frequently present in boys (the testicles do not drop into the scrotum, and remain in the abdominal cavity).
ead and face abnormalities may be present. The ears may be of irregular shape and may be lower or higher. The mandible and the mouth may be strikingly small. The nose is often curved upward. The eyes can be set wide apart, with droopy upper eye lids. The iris may have holes.
Furthermore, deformities of the limbs may frequently occur as well. Fingers and toes may cover each other; the second and third toes are frequently fused. The heels of the baby may be directed inwards, and the sole of the foot may be curved. Children who reach a higher age prefer to stand with their feet crossed.
Due to the smaller than normal pelvis, the movement of the pelvis is limited in some of these children. The sternum may also be shorter than normal.
Developmental kidney disorders and hereditary heart development disorders are common. One of the most common heart conditions is the underdevelopment of the tissue separating the heart chambers from each other. Imperfect closure of the two large heart arteries (aorta and pulmonary artery) may often occur as well.
Due to heart and breathing problems, the symptoms are frequently life-threatening, which may lead to the death of the child as early as newborn age or early childhood.