Which feature is commonly observed in osteogenesis imperfecta type IV?

• A. Bowing of long bones
• B. Increased scleral hue
• C. Hyperextension of joints
• D. Normal bone density

Answer: (A)

Fragile bones from defective type I collagen produce fractures that deform the skeleton as a child grows. In osteogenesis imperfecta type IV, repeated fractures and imperfect healing commonly cause the long bones to bend, producing noticeable bowing and curved limbs as the child grows. This skeletal deformity is a hallmark of the moderate, deforming form of the condition.

Blue sclera is more characteristic of other OI types and can be variable in type IV, so relying on scleral color isn’t as defining. Hyperextension of joints isn’t a defining feature of this form, and normal bone density would contradict the underlying fragility of bone in OI, where bone mass is typically reduced.