Benign familial hyperphosphatasemia: a report of two families and review of the literature.

Benign familial hyperphosphatasemia is a rare biochemical abnormality of hereditary nature, characterized by the presence of persistently elevated levels of serum alkaline phosphatase in several members of the same family, in the absence of disease or any known cause of hyperphosphatasemia. To date, there have been 29 pedigrees reported in the literature. Another two families affected with hyperphosphatasemia, originating in an increase in the bone isoenzyme, are described. The epidemiology, inheritance, isoenzymatic patterns, postulated mechanisms and clinical significance of this entity are discussed.