Mortality in various types of osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a group of closely related inherited diseases characterized by abnormal bone fragility. The current clinical classification system delineates 6 types, one of which (type II) is so severe that mortality is 100%, either intrauterine or perinatal. The types are differentiated by clinical groups, by severity, and by the presence or absence of other features such as blue sclerae or dentinogenesis imperfecta. There are no known previous studies of mortality in OI.

From a registry created in association with the Brittle Bone Society, 743 patients with OI in England and Wales were observed in the period 1980-1993. These were classified into 3 groups (type IA, type III, and types IB, IVA, and IVB combined). Average annual mortality rates were determined in each group by sex and attained age. These rates were compared with 1981 rates in the population of England and Wales, matched by sex and age. Results are given in terms of exposures, observed and expected deaths, and 2 indices of excess mortality: mortality ratios and excess death rates per 1000 person-years.

In type IA, 51.5% of the OI cases overall, there was no significant excess mortality (mortality ratio 108%, based on 15 deaths). In type III, on the other hand, excess mortality was very high in children and still significantly high at ages 15-34 years. In the combined group of types IB, IVA, and IVB, the mortality ratio was 157% in patients aged 45 and up (not significant at the 95% confidence level), but higher ratios at younger ages were significant, even though based on a total of only 5 deaths.