Carpenter syndrome is an extremely rare condition affecting the skull and facial bones, as well as the bones of the hands and feet. It is estimated to occur in approximately 1 in 1,000,000 births.
Cause of Carpenter syndrome
Carpenter syndrome is most likely caused by a mutation in the RAB23 gene, located on chromosome 6. In contrast to many craniofacial syndromes, this mutation is passed in an autosomal recessive fashion. This means that each parent must have the abnormal RAB23 gene and that both parents must pass on the abnormal gene to their baby in order for the child to be born with Carpenter syndrome. When both parents are carriers of the gene, there is a 1 in 4 chance that they may have a baby with Carpenter syndrome.
Carpenter syndrome is characterized by abnormal fusion of the cranial sutures. Sutures are specialized joints between the plates of bone that make up the skull. The sutures allow rapid expansion of the skull bones during the early years of life as the brain undergoes a period of rapid growth. When some of the cranial sutures fuse abnormally, as occurs in Carpenter syndromes, this most often leads to an abnormal skull shape. Children with Carpenter syndrome often develop a characteristically tall and pointed skull shape.
In addition, children with Carpenter syndrome may also be born with underdeveloped bones of the midface, a high arched palate (or roof of the mouth) and low-set, small ears. These children also frequently have abnormalities of the hands and feet, including the presence of extra digits, webbing of the fingers or toes and shorter than normal digits. Heart defects are also common in children with Carpenter syndrome as are developmental delays.
The diagnosis of Carpenter syndrome may first be suspected based on the abnormal skull shape and characteristic facial features. The suspected diagnosis is confirmed by a blood test to check for the RAB23 gene mutation. This genetic work-up is often overseen by a geneticist who is familiar with craniofacial syndromes.
The treatment of Carpenter syndrome is focused on correction of the abnormal skull shape and mirrors the treatment of craniosynostosis. Although the timing of surgery can be highly individualized, surgical correction of the craniosynostosis associated with Carpenter syndrome is most often initiated between 6 and 12 months of age. Surgery is usually performed through a scalp incision that lies concealed within the hair of the head. Your craniofacial surgeon will work in concert with a pediatric neurosurgeon in order to safely remove the bones of the skull. Then, the craniofacial surgeon reshapes and repositions those bones to give a more normal and enlarged skull shape which improves the appearance of the skull and gives more room for the brain to grow and develop.
Following surgery, your baby will spend at least one night in the pediatric intensive care unit prior to being transferred to a pediatric ward bed. You can anticipate that your baby will spend anywhere from 2-5 days in the hospital following craniosynostosis surgery.
In addition to surgical correction of the craniosynostosis, children with Carpenter syndrome may also require surgical correction of their cardiac defects. In some instances, these children may also benefit from surgery to remove extra fingers or toes or to separate digits that are joined together.