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# Osteogenesis imperfecta

An inherited type I collagen disorder that makes bones fragile: they break with minimal force; blue sclerae and deafness are common.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Femur](https://durgical.com/en/anatomy/femur/)
- [Tibia](https://durgical.com/en/anatomy/tibia/)
- [Sclera](https://durgical.com/en/anatomy/sclera/)
- [Stapes](https://durgical.com/en/anatomy/stapes/)
- [L1 vertebra](https://durgical.com/en/anatomy/lumbar-vertebra/)
- [T12 vertebra](https://durgical.com/en/anatomy/t12/)

## In biochemistry

- [Collagen synthesis](https://durgical.com/en/biochemistry/topics/collagen-synthesis/)
- [Collagen](https://durgical.com/en/biochemistry/enzymes/collagen/)
- [Hydroxyproline](https://durgical.com/en/biochemistry/molecules/hydroxyproline/)

## In histology

- [Connective tissue proper: cells and fibres](https://durgical.com/en/histology/connective-tissue-proper-cells-and-fibres/)
- [Bone tissue: cells, compact and spongy bone](https://durgical.com/en/histology/bone-tissue-cells-compact-and-spongy-bone/)
- [Extracellular matrix: collagen types, elastin, ground substance](https://durgical.com/en/histology/extracellular-matrix-collagen-types-elastin-ground-substance/)

## In embryology

- [Teeth](https://durgical.com/en/embryology/teeth/)

## Why it happens

- [How a single gene causes disease: enzymes, receptors and structural proteins](https://durgical.com/en/general-pathology/how-a-single-gene-causes-disease-enzymes-receptors-and-structural-proteins/)

## What it is

A group of inherited connective-tissue disorders, nearly always from COL1A1 or COL1A2 variants, with bone fragility and repeated fractures (“brittle bone disease”).

## Who gets it

Affects about 1 in 10,000 to 20,000 people worldwide. No Colombia-specific data were found; care is given in genetics and paediatric orthopaedic services.

## Causes

- COL1A1 or COL1A2 variants (≈ 90 % of cases), autosomal dominant; many are new (no family history)
- Rare recessive forms from genes that modify or fold collagen (CRTAP, P3H1, PPIB, SERPINF1 and others)

## Risk factors

- An affected parent (50 % chance of inheriting it in dominant forms)
- Germline mosaicism in healthy parents (explains some affected siblings)

## Pathophysiology

Type I collagen is a trimer of two α1 and one α2 chains. If a variant lowers the number of normal chains (null allele), half the usual amount of good-quality collagen is made: a mild form (type I). If it changes a glycine of the Gly–X–Y repeat, the abnormal chain enters the trimers and spoils them (dominant-negative effect): the triple helix folds late, is over-modified and degraded, giving severe forms (II, III, IV). Bone ends up with little matrix and disordered mineralisation; dentine, [sclera](https://durgical.com/en/anatomy/sclera/) (thin, showing the blue [choroid](https://durgical.com/en/anatomy/choroid/)) and the ear ossicles are also affected.

## Classification

- Type I: mild, non-deforming, blue sclerae, deafness in adulthood
- Type II: lethal in the perinatal period, fractures in utero
- Type III: progressively deforming, very short stature
- Type IV: moderate, normal or grey sclerae

## Symptoms and signs

- Fractures from minimal trauma, especially in childhood
- Blue or grey sclerae
- Hearing loss from adolescence or adulthood
- Dentinogenesis imperfecta (opalescent, fragile teeth)
- Short stature, bowing of long bones and scoliosis
- Ligament laxity and thin [skin](https://durgical.com/en/anatomy/skin/)

## Red flags

- Headache, cranial nerve signs or weakness (basilar invagination)
- Breathing difficulty from severe [chest](https://durgical.com/en/anatomy/region/chest/) deformity
- Multiple fractures in an infant: distinguish from child abuse

## Diagnosis

**Clinical**
Fractures from minimal trauma plus blue sclerae, dentinogenesis imperfecta, deafness or a family history.

**Tests**
Genetic testing of COL1A1, COL1A2 and recessive genes; calcium, phosphate, alkaline phosphatase and vitamin D to rule out other causes; audiometry.

**Imaging**
X-rays: osteopenia, fractures at different stages, thin bowed long bones and Wormian bones in the skull; bone densitometry (DXA); prenatal ultrasound in severe forms.

## Treatment

**Medical**
Bisphosphonates to raise bone density and reduce fractures, especially in children with moderate or severe forms

**Surgical**
Intramedullary rods (including telescopic rods that grow with the child) to correct deformity and prevent fractures

**Rehabilitation**
Physiotherapy, hydrotherapy and mobility aids that build strength without stressing bone

**Procedure**
Hearing aids or [stapes](https://durgical.com/en/anatomy/stapes/) surgery when hearing is lost

**Follow-up**
Follow-up of [spine](https://durgical.com/en/anatomy/region/spine/), hearing, teeth and breathing

## Complications

- Deformity and motor disability
- Scoliosis and respiratory failure
- Deafness
- Basilar invagination

## Prognosis

Highly variable: type I has a near-normal life expectancy; type II is usually fatal at birth; in type III respiratory failure is the main cause of death.

## Prevention

- Genetic counselling and prenatal diagnosis in affected families

## Test yourself

Think of the answer, then tap the question to see it.

## Which genes cause most cases of osteogenesis imperfecta?

COL1A1 and COL1A2, which encode the chains of type I collagen (≈ 90 % of cases).

## Why does a glycine change in collagen cause a severe form?

Glycine is the only residue that fits the centre of the triple helix; the abnormal chain enters the trimers and damages them (dominant-negative effect).

## Why do the sclerae look blue?

The collagen-poor sclera is thin and lets the colour of the underlying choroid show through.

## What must multiple fractures in an infant with osteogenesis imperfecta be distinguished from?

Child abuse; sclerae, teeth, family history, X-rays and genetic testing help.

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## Related conditions

- [Ehlers–Danlos syndrome](https://durgical.com/en/conditions/ehlers-danlos-syndrome/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Osteogenesis imperfecta: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/osteogenesis-imperfecta/) (MedlinePlus, US National Library of Medicine, 2026); [Osteogenesis imperfecta: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/001573.htm) (MedlinePlus, US National Library of Medicine, 2026); [COL1A1 gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/col1a1/) (MedlinePlus, US National Library of Medicine, 2026); [COL1A2 gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/col1a2/) (MedlinePlus, US National Library of Medicine, 2026).

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Source: https://durgical.com/en/conditions/osteogenesis-imperfecta/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/osteogenesis-imperfecta/