Osteogenesis Imperfecta defined -a genetic disorder of the bones causing them to be brittle and easily broken because of a gene-related mutation of collagen.
DOminant FORMS OFO.I.
Type I - most common and mildest - Bones fracture easily - Normal stature - Loose joints and weak muscles - Whites of eyes have blue, purple, or gray tint - Minimal/no bone deformity - Hearing loss possible at 20-30 yrs
Type II - most severe form - Lethal at or after birth - Severe bone deformity - Small stature -underdeveloped lungs - Tinted eyes
Type III - Bones fracture easily - may have fractures at birth - Short stature - Tinted eyes - Loose joints & Poor muscle development - Barrel-shaped rib cage - triangular face - Possible respiratory problems
Type IV -Between Type I and Type III in severity. -Bones fracture easily -Most fractures occur before puberty -Shorter than average stature -Sclerae are normal in color -Mild to moderate bone deformity -Tendency toward spinal curvature -Barrel-shaped rib cage -Triangular face -Brittle teeth possible -Hearing loss possible -Collagen improperly formed.
Type V -Clinically similar to Type IV in appearance and symptoms of OI. -A dense band seen on x-rays adjacent to the growth plate of the long bones. -Unusually large calluses (hypertrophic calluses) at the sites of fractures or surgical procedures. -Calcification of the membrane between the radius and ulna. (This leads to restriction of forearm rotation) -White sclera -Normal teeth -Bone has a “mesh-like” appearance when viewed with microscope -Dominant inheritance pattern
Type VI -Clinically similar to Type IV in appearance and symptoms of OI. -The alkaline phosphatase (an enzyme linked to bone formation) activity level is slightly elevated in OI Type VI. -This can be determined by a blood test. -Bone has a distinctive “fish-scale” appearance when viewed under the microscope. -Diagnosed by bone biopsy. -Whether this form is inherited in a dominant or recessive manner is unknown, but researchers believe the mode of inheritance is most likely recessive. -Eight people with this type of OI have been identified.
Recessive Forms ofO.I.
Type VII -The first described cases resemble Type IV OI in many aspects -In other instances the appearance and symptoms are similar to Type II lethal OI, except infants had white sclera, a small head and a round face. -Short stature -Short humerus (arm bone) and short femur (upper leg bone) -Coxa vera is common (the acutely angled femur head affects the hip socket) -Results from recessive inheritance of a mutation to the CRTAP (cartilage-associated protein) gene -Partial function of CRTAP leads to moderate symptoms while total absence of CRTAP was lethal in all 4 identified cases. Type VIII-Resembles lethal Type II or Type III OI in appearance and symptoms -except that infants have white sclera. -Severe growth deficiency. Extreme skeletal under mineralization. -Caused by a deficiency of P3H1 (Prolyl 3-hydroxylase 1) due to a mutation to the LEPRE1 gene.