In what type of disease is a "cotton wool" pattern in bone commonly observed?

The presence of a "cotton wool" pattern in bone is most commonly associated with Paget's disease. This condition is characterized by abnormal and excessive remodeling of bone, leading to the formation of structurally disorganized and enlarged bones. The "cotton wool" appearance refers to the radiological finding that presents as areas of radiolucency and radiopacity within the affected bones, resembling a fluffy, cotton-like texture.

Paget's disease typically affects the pelvis, skull, spine, and long bones. The altered bone structure can lead to symptoms like bone pain, deformity, and an increased risk of fractures. The distinctive cotton wool appearance is a reflection of the chaotic bone remodeling processes that occur, featuring areas of both increased and decreased density.

In contrast, other conditions listed in the question do not exhibit this specific radiological pattern associated with Paget's disease. Dentinogenesis imperfect pertains to dental formation issues and does not affect bone structure in the same way. Fibrous dysplasia involves the abnormal growth of fibrous tissue in bones, leading to a different presentation on imaging. Pemphigus vulgaris is an autoimmune disease primarily affecting the skin and mucous membranes, without any characteristic bone pattern observed in radiology.