The enthesopathy of vitamin D-resistant osteomalacia in adults

A case of an adult patient with vitamin D-resistant osteomalacia or X-linked hypophosphatemic osteomalacia (XLH) with diffuse calcification of entheses was reported. XLH is the most frequent cause of rickets in developed countries. It is characterized by an impaired renal transport of the phosphate and mutation of PFEX (phosphate regulating gene, with homologies to endopeptidase on the X-chromosome). In childhood, the classic clinical presentation includes short stature and bow leg. While at this age the main radiographic features are characterised by rickets, in adult life they are dominated by a generalised calcific enthesopathy. Concerning the pathogenesis of the enthesopathic lesions of XLH, no convincing hypothesis has yet been made. As in our patient, the extension and the severity of enthesopathy seems not related to the severity of the biochemical changes nor to the treatment with calcitriol. The calcified enthesopathy is an integral part of XLH and it is possible that it is found in adult because many years are necessary to produce it.