Type III is distinguished among the other classifications as being the "Progressive Deforming" Type. Type III is the next most severe form of Osteogenesis Imperfecta after Type II. It is the most severe form in which survival extends beyond the prenatal period. Type III Osteogenesis Imperfecta also has improperly formed collagen and often severe bone deformities plus additional complications.

It is common for a person with this type to have experienced 100 fractures by the time he or she reaches puberty. There are often fractures present at birth and X-rays may even show healed fractures that occurred before birth. Lifespan may be normal, albeit with severe physical handicapping. Loose joints and poor muscle development in their arms and legs making it impossible for them to ever accomplish walking.

Osteogenesis Imperfecta Type III can affect as many as one in sixty thousand people. Its hallmark feature is severe bone fragility and Osteopenia, which is progressively deforming. The mode of inheritance is thought to be autosomal recessive. People with type III Osteogenesis Imperfecta are generally shorter than average. They may have spinal deformities, respiratory complications, and brittle teeth.

Some of the characteristics of Type III Osteogenesis Imperfecta include ...

• Known as severe progressively deforming Osteogenesis Imperfecta.

• Short stature (some people only grow three feet tall).

• The sclera has variable hues, may be blue, purple, or grey tint.

• Abnormal collagen.

• In utero fractures are common.

• Soft bones that not only break easily but also bend.

• Loose joints and poor muscle development in arms and legs.

• They have major spinal curvature causing chronic back pain and respiratory problems.

• Barrel-shaped ribcage.

• They will always use a wheelchair for mobility throughout their entire life span.

• Their organs, which are the same size as any normal person's, are restricted within the smaller rib cage and because of this they experience problems with their organs.

• As with other types of OI, they have a triangular shaped face.

• Poor tooth development, often causing teeth to be brittle and discolored.

• Possible hearing loss.

• Possible respiratory problems.

• Poor tooth development, often causing teeth to be brittle and discolored.

• May live into adulthood.

• Vertigo is common in patients with severe OI.

• Constipation and hernias are also common in people with OI.