Description

• Inherited abnormality of procollagen amino acid sequence
• “Brittle bone disease”
• Bone hypomineralization and incomplete ossification result in brittle bones
• Incidence is 1/20,000 live births
• Abnormal collagen affects all connective tissue to varying degrees
• Time course is variable:
  • Most cases involve fractures during childhood followed by quiescence during adolescence and early adulthood

Etiology

• Procollagen defects result in abnormalities of bone and connective tissue matrix
• Defects in different sites on procollagen protein chain result in more severe forms
• Defects are inherited, either autosomal recessive (generally milder) or autosomal dominant (more severe)
• Lethal cases involve sporadic or new mutations
• Ehlers–Danlos syndrome involves mutations of the same procollagen protein in different locations

• Most cases involve pathologic fractures during childhood
• Multiple fractures often initiate evaluation for nonaccidental trauma, but the possibility of pathologic fractures also should be considered