This is a genetic condition characterized by the bones that break easily sometimes for no known reason. This develops because of the mutation in several different genes that don’t effectively work which can affect the normal production of collagen. The severity of the condition varies among the affected case with some only experiencing just a few fractures to others having several hundred fractures in their lifetime. There are around VIII identified forms of OI from type I through type VIII which are distinguished by their symptoms and genetic factors. Type I is the milder form of the condition and type II is the severe form as the infants often die shortly after birth from life-threatening breathing problems.
Type I
This accounts for around 50% of the OI cases and is characterized by mild bone fragility, minimal limb deformities and few fractures. They can also present compression fractures of the vertebrae, chronic pain, hearing loss that occurs in young adulthood, gross motor developmental delays, muscle weakness and joint and ligament weakness.
Type II
This severe form presents very short limbs, small chests, soft skulls, underdeveloped lungs, respiratory and swallowing problems. They also present numerous fractures, severe bone deformity and the improper formation of the collagen. The infants are low birth weight and usually die within weeks of delivery.
Type III
This is considered to be one of the most severe forms that is characterized by the structurally defective type I collagen. The infants have mildly shortened and bowed limbs, multiple fractures at birth, bowing and progressive malformation of the long bones. They also have short stature, loose joints and poor muscle development of the arms and the legs, spinal curvature and hearing loss in some case.
Type IV
This condition can be mild to severe and the fractures may not occur until the child begins to walk. They also present moderate to severe growth retardation, bowing of the long bones, shorter than average stature and possible hearing loss. The barrel-shaped rib cage may be detected, hearing loss possible and the brittle teeth can be apparent in some case.
Type V
The features of this type appear to be similar to type IV presenting unusually large calluses at the sites of fractures, calcification of membranes between the bones of the forearm which can restrict the rotation of the forearm and the bone may appear to be mesh-like when examined under the microscope.
Type VI
This is an extremely rare form appearing to be moderate in severity presenting signs similar to type IV. This type is distinguished from the other forms by the mineralization defect that is evident when the biopsied bone is examined.
Type VII
This type appears to be similar to type IV in several aspects of its appearance and symptoms while some cases may resemble the type II. This type presents short leg bones, short arm bone and short stature.
Type VIII
This type appears to resemble the type II or type III in symptoms except for the white sclera among the infants. Among the children of this type, the severe growth deficiency occurs and the extreme under-mineralization of the skeleton is also evident.
References
http://www.oif.org/site/PageServer?pagename=AOI_Types
https://ghr.nlm.nih.gov/condition/osteogenesis-imperfecta
https://rarediseases.org/rare-diseases/osteogenesis-imperfecta/
