The brittle bone diseases are a large group of conditions characterised by excessive fragility of the bones present from childhood. The severity of the condition may vary.
Some affected individuals have multiple fractures, in others the condition is difficult to diagnose.
It is conventional to describe four varieties of osteogenesis imperfecta. Type II usually causes such severe fractures that infants are stillborn or die in the first few weeks of life. Type III is severe but consistent with good survival although there may be markedly impaired growth. Types I and IV are milder conditions with good stature and relatively few fractures. Associated problems may include lax joints, fragile teeth, excessive sweating and easy bruising.