Osteogenesis imperfecta (OI), also known as brittle bone disease is a collection of genetic disorders that typically affect the bones. The term means imperfect bone formation. For people with this condition bones break easily, often from very light taps or with no reason at all. They suffer frequent multiple fractures, and in serious cases fractures may happen even before birth. Milder cases usually suffer a few fractures over their lifetimes.

There are 8 types of osteogenesis imperfecta. The mildest form is Type I and the most serious is type II. The other types fall between these 2 categories and have overlapping signs & symptoms. Nowadays, genetic factors are used to categorise the osteogenesis imperfecta diagnosis uses into its different types. While OI is often diagnosed based on clinical symptoms, clinical geneticists may run biochemical (collagen) or molecular (DNA) tests to assist in OI diagnosis of OI in certain cases. Usually there's a wait of several weeks before test results are known.

Type I

- Most common and mildest form
- Bones fracture easily
- Most fractures occur before puberty
- Normal or near-normal height
- Loose joints and muscle weakness
- Whites of the eyes (sclera) usually have a blue, purple, or grey tint
- Triangle-shaped face
- Brittle teeth possible
- Collagen structure is normal, but the amount is less than normal

Type II

- Most serious - often fatal at or shortly after birth, usually due to breathing problems
- Numerous fractures and severe bone deformity
- Small stature with underdeveloped lungs
- Tinted sclera
- Collagen improperly formed

There is no cure for OI so far. Treatment focusses on avoiding or controlling the symptoms, increasing self-dependent movement, and maximising bone mass & muscle strength with regular exercise. Care of fractures, extensive surgical and dental procedures, and physical therapy are often recommended for people with OI. Mobility aids like wheelchairs, braces, are frequently used by more severe types of OI.

Swimming and water therapy allows independent movement with little danger of fracture. For other who can, walking with or without mobility aids is good exercise. Suitable and safe exercise must be recommended by the physician and/or physical therapist.

Maintaining a healthy weight, eating a nutritious diet, and avoiding smoking, excessive alcohol and caffeine and staying from steroid medications improves health of children & adults diagnosed with OI.

Medicines like growth hormone treatment, treatment with intravenous and oral drugs called bisphosphonates, an injected drug called teriparatide (for adults only) and gene therapies are being researched for their potential effectiveness in treating this disease.