Metabolic bone disease

Bone is a complex organ that is highly metabolically active, particularly in children. Normal metabolism is dependent upon the three main elements, matrix, mineral and cells that are integral components of bone. In addition, there are several humoral factors that also influence bone. Abnormalities in any of these components can give rise to metabolic bone disease. Abnormalities of mineralisation are the commonest manifestation of metabolic bone disease although some are ultimately derived from problems within the supporting cellular components. On the one hand these present themselves as osteomalacic conditions that principally show themselves as mineralisation defects within the growth plates, a condition that is known as rickets, whilst more generalised mineralisation defects, known as osteoporosis are principally caused by Osteogenesis Imperfecta but can also present as a secondary phenomenon following, for instance, prolonged steroid therapy. Conversely, there are several rarer conditions that cause an increase in bone density, some of which cause a decrease in bone fragility but some which, paradoxically are associated with increased tendency to fracture. Many of these conditions have a genetic origin. This article summarises these conditions.