Osteitis fibrosa cystica

Osteitis fibrosa cystica /ˌɒstiːˈaɪtᵻs faɪˈbroʊsə ˈsɪstᵻkə/, abbreviated OFC, also known as osteitis fibrosa, osteodystrophia fibrosa, and Von Recklinghausen's disease of bone (not to be confused with Von Recklinghausen's disease, neurofibromatosis type I), is a skeletal disorder caused by hyperparathyroidism, which is a surplus of parathyroid hormone from over-active parathyroid glands. This surplus stimulates the activity of osteoclasts, cells that break down bone, in a process known as osteoclastic bone resorption. The hyperparathyroidism can be triggered by a parathyroid adenoma, hereditary factors, parathyroid carcinoma, or renal osteodystrophy. Osteoclastic bone resorption releases minerals, including calcium, from the bone into the bloodstream. In addition to elevated blood calcium levels, over-activity of this process results in a loss of bone mass, a weakening of the bones as their calcified supporting structures are replaced with fibrous tissue (peritrabecular fibrosis), and the formation of cyst-like brown tumors in and around the bone. The symptoms of the disease are the consequences of both the general softening of the bones and the excess calcium in the blood, and include bone fractures, kidney stones, nausea, moth-eaten appearance in the bones, appetite loss, and weight loss.