Procollagens

[AnBGilbert]

I am waiting to get in to see a doctor for my son. Osteogenesis runs in his fathers side of the family. Our pediatrician just got procollagen levels back, he is at 1270, and refered us to a specialist...with no more information. Im trying to read what I can online, but its hard to understand. Where Im confussed is everything says that type1 OI has decreased procollagen level and also something about there being a diffrence in being just a carrier and actually having it. Could someone please explain this procollagen enzyme to me(in a language I can understand)?

[Jordanna Joaquina, MS, CGC]

As you know, osteogenesis imperfecta (OI) is a group of genetic disorders that mainly affect the bones. There are at least eight recognized forms of osteogenesis imperfecta, designated type I through type VIII. The types can be distinguished by their signs and symptoms, although their characteristic features overlap.

Most of the mutations that cause osteogenesis imperfecta type I occur in the COL1A1 gene. These mutations typically reduce the amount of functional type I collagen produced in the body. This type of collagen is the most abundant protein in bone, skin, and other connective tissues that provide structure and strength to the body. A defect in the structure of type I collagen weakens connective tissues, particularly bone, which causes bones to be brittle and to fracture easily.

Most cases of osteogenesis imperfecta have autosomal dominant inheritance, which means one copy of the altered gene in each cell is sufficient to cause the condition. An affected person has a 50% chance with each pregnancy to have an affected child. Many people with type I osteogenesis imperfecta inherit a mutation from a parent who has the disorder.

Less commonly, osteogenesis imperfecta has autosomal recesssive inheritance. Autosomal recessive inheritance means two copies of the gene in each cell are altered. The parents of a child with an autosomal recessive disorder typically are not affected, but each carry one copy of the altered gene. Two carriers have a 25% chance with each pregnancy to have an affected child.

We recommend that you and your son meet with a medical geneticist, who can perform a physical exam as well as review test results, your son's medical history and family history. A medical geneticist can be found at the American College of Medical Genetics website. We hope this information is helpful and wish your family the best.