A female infant, delivered at 37 weeks' gestation, presents with severe bowing of long bones. Physical examination shows blue sclera and x-rays show broad and crumpled long bones. As the attending physician, you suspect a disorder in connective tissues and order an evaluation of collagen gene defects. Results demonstrate the infant harbors a mutation in theCOL1A1gene. The presenting symptoms and molecular analysis indicate this child is suffering from which of the following disorders?

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Quizplus · Accepted Answer

The symptoms and mutation in the COL1A1 gene are indicative of osteogenesis imperfecta, a disorder characterized by brittle bones, blue sclera, and defects in type I collagen.  Osteogenesis imperfecta consists of a group of at least 4 types (mild, extensive, severe, and variable). The disorder is characterized by brittle bones and abnormally thin sclerae, which appear blue owing to the lack of connective tissue. The symptoms arise due to defects in 2 a-collagen genes, the COL1A1 and COL1A2 genes. There have been over 100 mutations identified in these 2 genes. The mutations lead to decreased expression of collagen or abnormal pro1 proteins. The abnormal proteins associate with normal collagen subunits, which prevents the triple helical structure of normal collagen to form. The result is degradation of all the collagen proteins, both normal and abnormal.

A Female Infant, Delivered at 37 Weeks' Gestation, Presents with Severe