Osteitis fibrosa cystica is commonly associated with hyperparathyroidism. Hemorrhagic cystic lesions (brown tumors) usually occur in the long bones. Treatment is parathyroidectomy Osteomalacia is defined as a defect in mineralization of adult bone that results from abnormalities in vitamin D metabolism. Treatment generally involves vitamin D supplementation. Osteogenesis imperfecta is a genetically determined disorder in the structure or processing of type I collagen. Treatment is surgical and involves orthoses to prevent fractures and correction of deformities by multiple osteotomies. Osteitis deformans is also known as Paget's disease. Osteopetrosis is a rare skeletal deformity associated with increased density of the bones.