A chronic bone disease that is characterized by the abnormal breakdown of bone followed by abnormal bone formation is known as

Paget's disease

Explanation:

When cellular deforming and remodelling of many bones takes place and this occurs as a chronic condition then this is known as Paget's disease. There is excessive breakdown of bone as well as disorganised formation of new bones. Such problem leads to weakening of the bone due to which complications such as deformity, fracture and arthritis occurs. The disease does not spread from one bone to another and the entire skeleton is not affected in such a disease, it only affect few or more bones. There is currently no known cure for the disease.