Osteogenesis Imperfecta

Abnormality of Type I collagen

Term Osteogenesis imperfecta first used by Vrolick 1849

Classification

Silllence genetic classification 1979

Type	Genetics	Description
I	Autosomal dominant	Mildest form of OI Mild to moderate bone fragility without deformity Blue Sclera, early hearing loss, easy bruising May have mild to moderate short stature Type IA: dentinogenesis imperfecta absent Type IB: dentinogenesis imperfecta present
II	Autosomal dominant or recessive	Perinatal lethal or recessive Extreme fragility of connective tissue, multiple in utero fractures, usually intrauterine growth retardation Soft, large cranium Micromelia, long bones crumped and bowed, ribs beaded
III	Autosomal dominant or recessive	Progressive deforming phenotype Severe fragility of bones, usually have in utero fractures Severe osteoporosis Relative macrocephaly with triangular facies Fractures heal with deformity and bowing White sclerae and extreme short stature, scoliosis
IV	Autosomal dominant	Skeletal fragility and osteoporosis more severe than type I Associaited with bowing of long bones, light sclerae +- moderate short stature, +- moderate joint hyperextensibilty Type IVA: dentinogenesis imperfecta absent Type IVB: dentinogenesis imperfecta present

Abnormality type I collagen.

Scoliosis of moderate to severe degree does not respond to bracing, when scoliosis exceeds 40º Spinal fusion is indicated.

Individual treatment of fractures

Medical management

Intravenous pamidronate has been shown to reduce fracture frequency in severe OI

Oral bisphosphonates are currently under study

Silence DO' Senn A, Danks DM; Genetic heterogeneity in osteogenesis imperfecta. J Med Genet 1979;16(2):101-16