Synonym: Brittle Bone Disease
Incidence: 1 in 20,000
Gene defect: Col1A1 (17q) and Col1A2 (7q)
Mnemonic: Remember “one” for “bone”. Collagen one is the main composition of bone. OI is a disorder of bone. Hence, the defect is is in Col1.
Features
Mnemonic: BLOOD
- Blue sclera
- Otosclerosis (SNHL)
- Osseous fragility
- Dentinogenesis imperfecta
| Sillence Type | Inheritance | Features | Mnemonic | Collagen |
| I | AD | Blue sclera, Otosclerosis; Osseous fragility (variable) – mild | BlO | Normal quality; Insufficient quantity |
| II | AD, AR | Lethal perinatal | L | Poor quantity and quality |
| III | AR | Osseous fragility (moderate to severe) – progressive deforming | O | Collagen poorly formed; normal quantity |
| IV | AD | Osseous fragility, Dentinogenesis imperfecta – deforming with normal sclera | OD | Sufficient quantity but poor quality |
Treatment
Mnemonic: BDSM
1. Basilar invagination: Bone resection via transoral approach
2. Deformities: Realignment osteotomy with rod fixation (Sofield-Miller procedure)
3. Scoliosis: Operate when curves >45 degrees in mild forms and >35 degrees in severe forms
4. Multiple fractures:
- Prevention: Bracing and Bisphosphonate
- <2 years old: Conservative
- >2 years old: Telescoping rods (Duval)
Reference:
- General Orthopaedics and Basic Science edited by Nikolaos K. Paschos, George Bentley
- Sillence DO, Senn A, Danks DM. Genetic heterogeneity in osteogenesis imperfecta. J Med Genet. 1979;16:101–116.