Benign osteopetrosis: a review of 42 cases showing two different patterns.

Radiographs of 42 patients with benign osteopetrosis were reviewed. Clinical notes were available for approximately half of these. According to the classification of Bollerslev and Andersen in 1987, 29 patients had type II disease of whom 18 sustained fractures. Thirteen patients had type I disease; only one of these patients sustained fractures. Transverse banding of the metaphyses was a common feature in type II disease; it was not seen in any of the type I cases. This review confirms that type II patients are at high risk of fracture, while type I patients are not. The presence of sclerotic metaphyseal bands distinguishes between the two types, its presence being enough to confirm type II. However, its absence is not an indication of type I disease, since it is not seen in all cases of type II. Banding does not correlate with liability to fracture. Typing patients with the benign form of osteopetrosis is important in order to anticipate the fracture pattern.