It is a recessive trait with males and females affected. Two copies of the mutant gene are needed to cause the disease. Clinically the disease is characterized by short limb dwarfism, thin skin, soft skull, unusually large fontanels (soft spots), blue sclerae (whites of the eyes, small nose, low nasal bridge, inguinal hernia and numerous bone fractures at birth. There is bowing of limbs due to multiple fractures This disease (also called osteogenesis imperfecta congenita) is usually not compatible with life. The children are usually stillborn or die of respiratory failure in early infancy. The condition results from mutations that impair the production of type I collagen, a key component of connective tissue. Mutations responsible for osteogenesis imperfecta type II have been identified in both the COL1A1 and COL1A2 genes. (COL1A1 is the gene for type 1 alpha-1 chain of collagen (COL1A1) and is located in chromosome17q21.31-q22.05. COL1A2 is the gene for type 2 alpha-chain of collagen (COL1A2) which is in chromosome 7q22.1).
Reviewed on 12/27/2018