A seven-month-old boy with a diagnosis of vitamin-D deficiency rickets is presented. After treatment with vitamin-D, biochemical and radiological improvement was noted. At 14-months of age the plasma alkaline phosphatase activity valve was found to be elevated even though rickets was not present. A diagnosis of hyperphosphatasemia was established. Although rare in infancy, transient hyperphosphatasemia may occur following vitamin-D deficient rickets. This possibility should be considered when evaluating laboratory results in such cases.

Keywords: vitamin-D deficient rickets, transient hyperphosphatasemia, alkaline phosphatase