Types of Ostegenesis Imperfecta
Type IV – Undefined
People with OI Type IV are moderately affected. Type IV can range in severity from relatively few fractures, as in OI Type I, to a more severe form resembling OI Type III. The diagnosis can be made at birth but often occurs later. Fracture might not occur until the child is already walking. People with Type IV OI have sufficient collagen quantity but has a poor collagen quality. General features of OI Type IV are the following:
- People with OI Type IV have moderate-to-severe growth retardation, which is one factor that distinguishes them clinically from people with Type I.
- The child’s height may be less-than-average for his or her age.
- Early loss of hearing
- Short stature, spinal curvature and barrel-shaped rib cage
- Bone deformity is mild to moderate
- Long bone fractures, vertebral compression, scoliosis, and ligament laxity may be present.
Type V – Moderate
OI Type V is moderate in severity. It is similar to OI Type IV in terms of frequency of fractures and the degree of skeletal deformity. General features of OI Type V are the following:
- Large, hypertrophic calluses in the largest bones at fracture or surgical procedure sites –the most conspicuous feature of this type
- Hypertrophic calluses arise spontaneously
Type VI – Extremely Rare; Moderate; Undefined mode of inheritance
OI Type VI is extremely rare. It is moderate in severity and similar in appearance and symptoms to OI Type IV. This type is distinguished by a characteristic mineralization defect seen in biopsied bone. General features of OI Type VI are the following:
- Same clinical features as Type IV.
- Distinguished histologically by “fish-scale” bone appearance.
Type VII – Undefined
The first described case of OI Type VII resembles Type IV OI in many aspects of appearance and symptoms. 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. General features of OI Type VII are the following:
- leg bones, humerus and femur are short
- Short stature is common
Type VIII – Undefined
Cases of OI Type VIII are similar to OI Types II or III in appearance and symptoms except for white sclerae. It is caused by absence or severe deficiency of prolyl 3-hydroxylase activity due to mutations in the LEPRE1 gene.
- Characterized by severe growth deficiency and extreme under-mineralization of the skeleton.