Hyperphosphatasemia: report of three cases.

We report the radiographic findings in three cases of hyperphosphatasemia. Often classified as a congenital bone dysplasia, the skeletal manifestations of this disorder are diagnostic. These features simulate Paget's disease both radiographically and with respect to salient biochemical markers. Typically, presentation is at early childhood with skull deformity, refusal to weight bear, and bowing of the extremities. Notable radiographic features include bowing of the long bones, thickening of the cortex, osteopenia, coarsened trabecular pattern, expansion of the medullary cavity, and thickening of the intramembranous portion of the calvarium. Histologic features include absence of lamellar bone and haversian systems, with thick osteoid seams and increased number of osteoclasts. An autosomal recessive pattern of inheritance has been suggested, although autosomal dominant varieties have been postulated.