Idiopathic retroperitoneal fibrosis--is serum alkaline phosphatase a marker of disease activity?

Two patients are presented in whom extensive investigations were carried out to determine the cause of a raised serum alkaline phosphatase. Idiopathic retroperitoneal fibrosis was diagnosed in both cases and the serum alkaline phosphatase returned to normal following treatment with corticosteroids and coincident with resolution of the patients' symptoms.