Osteogenisis imperfecta (OI) is "a rare genetic .
disorder of collagen synthesis associated with broad .
spectrum of musculoskeletal problems, most notably bowing .
and fractures of the extremities, muscle weakness, .
ligamentous laxity, and spinal deformities.".
(Binder, 386). Other collagen-containing extraskeletal .
tissues, such as the sclerae, the teeth, and the heart .
valves are also affected to a variable degree. OI has a .
"common feature of bony fragility associated with defective .
formation of collagen by osteoblasts and fibroblasts." .
(Smith, 1983, 13) This disease, involving defective .
development of the connective tissues, is usually the result .
of the autosomal dominant gene, but can also be the result .
of the autosomal recessive gene. Spontaneous mutations are .
common and the clinical presentation of the disease remains .
to be quite broad. (Binder, 386) .
OI is most commonly referred to as "brittle bones", .
but other names include: fragilitas ossium, hypolasia of .
the mesenchyme, and osteopsathyrosis. Osteogenisis .
imperfecta is still not completely understood, and while .
there have been advances in diagnosing the disease, .
treatment is still limited.
CAUSES.
Osteogenisis imperfecta is the result of mutations .
in the genes for type I collagen.
In the mild dominantly inherited form of OI (type I), " a .
non-functional allele for the alpha 1 (I) chain halves .
collagen synthesis," (Smith, 1995, 169) and is largely .
responsible for the inheritance. Single base mutations in .
the codon for glycine causes lethal (type II) OI by wrecking .
the formation of the collagen triple helix. Types III and .
IV are the "less dram- atic outcomes of similar glycine .
mutations in either the alpha 1 (I) or the alpha 2(I) .
chains.(Smith, 1995, 169).
The clinical signs can be caused from defective .
osteoblastic activity and defective mesenchymal collagen .
(embryonic connective tissue) and its derivatives, such as .
sclera, bones, and ligaments.