The Effects of Trisomy 13

The word trisomy in genetics translates to meaning “an extra” chromosome. In the case of Trisomy 13 or Patau Syndrome, it is an extra chromosome at position 13 in a karyotype. This means the individual possess three copies of the chromosome instead of two. This syndrome can be diagnosed with certainty through the use of amniocentesis, which allows the chromosomal make-up of the individual to be revealed.This particular type of trisomy means that there is an additional chromosome number thirteen.  This does have serious effects on the individual and their overall health.

Unfortunately, babies born with this disorder live an average of 2.5 days. This is usually due to the birth defects that are present. According to the National Institutes of Health, it is estimated that Patau Syndrome occurs in about  1 in 16,000 newborns, but exact numbers are hard to determine as many pregnancies end in preterm labor. Another large number of these pregnancies are terminated through early induction as their prognosis is grim after birth. Only about five to ten percent of the children born with this condition survive beyond their first year. This condition is not inherited and results from a random mutation in gametes (sex cells; eggs and sperm). 

The addition of the chromosome in Patau Syndrome has many consequences to the anatomical make up of the baby.  Polydactyly , or the presence of additional toes or fingers is common as is clenched hands (inner fingers are on top of outer fingers).  Children can also be born with a cleft palate, with varying degrees of severity.  At times the child is born with an abnormal nose or the nose is absent from the face. This can also lead to varying degrees of respiratory distress.

Microcephaly, or an uncommonly small head is also prevalent with this disorder. A large number of the children born with this disorder also have heart disorders in a majority of the cases. The eyes may also be extraordinarily close together, or at times fused. Micrognathia, or a small jaw is also one of the facial effects of this condition. The combination of the micrognathia and cleft palate can lead to the necessity for intervention and breathing devices at birth.

There are varying degrees of skeletal abnormalities that can occur with this condition. The resultant phenotype (observable traits) will depend on the expression of the disorder. Hernias also are symptomatic of this disorder, both umbilical and inguinal. The most unsettling characteristic of this disorder is the severe level of mental retardation that exists. The surviving children truly severely mentally retarded with little hope of improvement in this area.   

In all, Trisomy 13 is heartbreaking for the families that endure this condition. The mothers are often encouraged to have early induction to end the prolonged mental anguish from carrying a child with this disorder. Women will often go into preterm labor before the child is far enough along to survive. There are many support groups for parents of these children and grief support groups.