Osteomalacia, translated “soft bones”, was first recognised by the pathologist Pommer in 1885 as a specific illness and separate from osteoporosis. It is characterised by a mineralisation malfunction of the normally structured organic bone matrix in adults and histologically by a high proportion of non-mineralised osteoid (“wide seams of osteoid”) (Fig. 52.1a–d). Paradoxically, the total mass of the bone matrix is raised. Nevertheless, there is an increased risk of fracture. Mineralisation malfunctions of the growing skeleton, in addition, are accompanied by changes of the epiphysis and stronger deformities of the skeleton and are referred to as rickets.