Transient hyperphosphatasemia of infancy and early childhood (THI) is a benign condition characterised by transiently increased aktivity of serum alkaline phosphatase (S-ALP) in children under five years of age. Our patient with bilateral nephrolithiasis and a history of severe prematurity presented with high S-ALP, initially suggestive of disturbed bone metabolism.
However, the normal values of S-Ca, P, Mg, PTH, U-Ca/U-cr and normal wrist X-ray ruled out this possibility and pointed to the diagnosis of THI, which was further confirmed by the normalisation of S-ALP within one month.