The majority of patients with OI have a relatively mild disorder which improves over succeeding weeks and months. Most patients will eventually be free of symptoms. However, in some patients, the symptoms are more severe, the duration of the illness may be longer, and the expected recovery may not occur. Overall, on follow-up, the majority of patients with OI have improved. More than half of the patients remained on treatment. Those patients with antecedent events, such as a viral infection, appeared to do better overall than those who developed the condition spontaneously.