Type I OI-mild

The most common mutation causing OI type I causes a reduction in the production of otherwise normal type I collagen secondary to the effect of a null allele mutation. This means that Type I means too little of "normal" collagen.     Patients often have normal stature but a slightly low stature does not preclude the diagnosis of type I OI. "Type I OI" does not equal "mild OI". Individuals may have few or no fractures, mostly during the first years of life or even at birth, or numerous fractures throughout their lives. They may have triangular face but may have normal faces.  They are usually fully ambulatory, and do not have bowing of the long bones, although vertebral fractures may be present.  Most have blue sclera, but it can be white, or blue color may fade as the individual grows older. This condition is transmitted as an autosomal dominant trait. Despite the absence of fractures, bone density can be very low, with no relation with clinical severity, underscoring the relative lack of significance of bone density measurements assessing severity in patients with OI. In many instances bone density is normal during the first months of life, and individuals progressively fail to increase bone mineral density with age. In some cases the diagnosis is an incidental finding after a fracture. Dentinogenesis imperfecta can be present even in very mild cases. Early hypoacusia  and cardio-vascular problems, particularly aortic valvular disease can be present in these subjects. 

Most common and usually mildest type of Osteogenesis Imperfecta.
Bones predisposed to fracture. Most fractures occur before puberty.
Normal or near-normal stature.
Loose joints and low muscle tone.
Sclera (whites of the eyes) usually have a blue, purple, or gray tint.
Triangular face.
Tendency toward spinal curvature.
Bone deformity absent or minimal.
Brittle teeth possible.
Hearing loss possible, often beginning in early 20s or 30s.
Collagen structure is normal, but the amount is less than normal.

Type IV-moderate OI with short stature

These individuals typically have short stature, bowing of long bones, and vertebral fractures. Scoliosis and joint laxity may be present. Patients with this form of OI are generally able to ambulate, but they may require aids for walking. Based on the presence of DI, moderate OI has been sub-divided in two forms, "a" and "b". These patients have white sclera. Precise diagnosis of this type of OI is often difficult, as the clinical characteristics are not clear in the literature, and different centers base the diagnosis on different criteria.