Familial hyperphosphatasemia: diagnosis in early infancy and response to human thyrocalcitonin therapy.

Familial hyperphosphatasemia is an uncommon hereditary disorder of membranous bone with concurrent overproduction and overdestruction of bone and bone collagen by osteocytes. This process does not allow normal maturation into compact lamellar bone. Two cases of severely affected children are presented which demonstrate that the condition can be diagnosed in early infancy by abnormalities in the long bones. At this stage the skull may appear normal and the characteristic thickening of the calvarium appears later. The disease is treatable with human thyrocalcitonin; these and previously reported cases have responded favorably.