Osteogenesis Imperfecta : Mnemonic

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

1. Blue sclera
2. Otosclerosis (SNHL)
3. Osseous fragility
4. 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:

1. General Orthopaedics and Basic Science edited by Nikolaos K. Paschos, George Bentley
2. Sillence DO, Senn A, Danks DM. Genetic heterogeneity in osteogenesis imperfecta. J Med Genet. 1979;16:101–116.