In the vast majority of cases, bone alkaline phosphatase in children is not serious when it is 250 IU/dl, because the normal level of bone alkaline phosphatase in children is less than 200 IU/dl. Only after alkaline phosphatase reaches 500 IU/dl is a child considered to have a more typical vitamin D deficiency rickets, at which time children may develop occipital baldness, chicken chest, square skull, X-leg, O-leg, etc, O-leggedness, etc. Bone alkaline phosphatase in children is mildly elevated at 250 IU/dl, and most children do not have specific manifestations of rickets.