The term osteogenesis imperfecta (OI) is used for a group of disorders in which genetic defects result in abnormally brittle bones that fracture easily. A number of types have been described based on the severeity of disease. This group of disorders is also known as ‘brittle bone disease’.
The form of OI described here is extremely rare and has overlapping features with other forms caused by different gene mutations.
Some fetuses suffer bone fractures while in utero while others may suffer breaks during the birthing process or later. Repeated fractures in limb bones and abnormal curvature of the spine may result in shortness of adult stature. Involvement of the rib cage may lead to breathing difficulties and can be fatal.
The facial features can result in a distinctive appearance. The skull sutures do no form properly resulting in a malformed skull and hydrocephalus (increased pressure on the brain) in some infants. The midface is underdeveloped and the orbits containing the eyes can be shallow resulting in a prominent appearance and protrusion of the eyes. The white part of the eye (sclera) can be bluish in color.
This variant of osteogenesis imperfecta is inherited in an autosomal recessive pattern in which two copies of a specific mutation must be present. Those who carry only a single copy of the mutation such as the parents are clinically normal. Such parents can expect, however, that 25% of their children will inherit this condition.
This condition is usually diagnosed at birth or soon thereafter by pediatricians. Orthopedists, geneticists, and ophthalmologists may be involved in the diagnosis as well. Individuals with OI need to be handled gently to avoid further breakage. Fractures must be stabilized promptly and hydrocephalus also requires prompt treatment. When the bulging eyes interfere with normal blinking because of the shallow eye sockets, it may be necessary to reconstruct the bony orbital cavity. A drug known as pamidronate has been shown in some patients with OI to increase bone density and decrease the risk of fractures. Mobility can be seriously impaired. Depending upon the bones involved and the severity of this condition, lifespan may be limited to infancy or childhood.