Cortical defects- wormian bones- and dentinogenesis imperfecta
Overview
Osteogenesis imperfecta is one of the most common skeletal dysplasias. It is a generalized disease of connective tissue that may manifest itself with one or more of the following findings: blue sclerae, triangular facies, macrocephaly, hearing loss, defective dentition, barrel chest, scoliosis, limb deformities, fractures, joint laxity, and growth retardation. Additional features, such as constipation and sweating, may also occur. A multidisciplinary approach is required to manage the disease
Symptoms
* Type I osteogenesis imperfecta is the mildest and most common form. Patients present with blue sclerae (often described as dark blue with a gray tinge), variable degrees of bone fragility, moderate bone deformity, and premature deafness. Birth weights tend to be normal, although one or more bones may be fractured. Severely affected babies with type II disease are born with dwarfism, with blue sclerae and short, bowed limbs. Babies with type III disease are born with severe bone fragility and suffer multiple fractures at birth, although their birth weight tends to be normal. The sclerae are bluish at birth but fade over the years, becoming white in adulthood. Dentinogenesis imperfecta is frequently seen.
Causes
Type 1 collagen is a triple helix formed by 2 copies of the alpha1 chain and 1 copy of the alpha2 chain. The COL1A gene on chromosome 17 encodes the pro-alpha1 chain, and the COL2A gene on chromosome 2 encodes the pro-alpha2 chain.