Also called brittle bones, osteogenesis imperfecta is a hereditary disease of bones and connective tissue. It causes fragile bones, thin skin, blue sclera, poor teeth, hypermobility of the joints, and progressive deafness.
The disease occurs in many forms. In the rare congenital form, in which fractures are present at birth, the patient usually dies during the first few days or weeks after birth. In the late-appearing form (osteogenesis imperfecta tarda), the child appears normal at birth but develops recurring fractures - mostly of the extremities - after age 1.
Some children with osteogenesis imperfecta tarda have gross multiple fractures and deformities; others have an increased tendency to fracture but no significant deformities. Some have multiple fractures during childhood, improve after puberty, and then begin to fracture more frequently later in life, particularly during pregnancy and then again after menopause.
Causes and pathophysiology
Osteogenesis imperfecta may result from autosomal dominant or recessive inheritance. Clinical signs may result from defective osteoblastic activity and defective mesenchymal collagen (embryonic connective tissue) and its derivatives (sclera, bones, and ligaments). The reticulum fails to differentiate into mature collagen or may cause collagen to develop abnormally, leading to immature and coarse bone formation. Cortical bone thinning also occurs.
Signs and Symptoms
In the four most common types of OI, symptoms may include:
X-rays show evidence of multiple old fractures and skeletal deformities. A skull X-ray shows wide sutures with small, irregularly shaped islands of bone (wormian bones) between them. These findings can help differentiate osteogenesis imperfecta from child abuse.
Serum calcium and serum phosphorus levels are normal.
Analysis of deoxyribonucleic acid may reveal the diagnosis in some families.
Because no cure exists, the goal of treatment is to prevent deformities through the use of traction, immobilization, or both and to aid normal development and rehabilitation. Limb deformities may be corrected by multiple osteotomies and rod placement.
Other measures include assessing for and treating scoliosis, a common complication, and promoting preventive dental care and repair of dental caries.
Patients with mild osteogenesis imperfecta may need little treatment after age 15, when the fracture rate begins to decrease. Women need special attention during pregnancy and after menopause, when their tendency to fracture may return.
Genetic counseling is recommended for prospective parents if one or both are affected by this disorder.
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