Transient hyperphosphatasemia of infancy and childhood: A study of serum alkaline phosphatase by electrofocusing techniques

Objective. - To evaluate serum alkaline phosphatase (ALP) isoenzymes, using a sensitive electrofocusing technique, in transient hyperphosphatasemia of infancy and childhood. Design. - Randomized study of infants and children who provided serum samples when an unusual magnitude of total ALP activity was noted. Setting. - Reference enzyme laboratories in Gorizia and Bergamo (Italy) and in Charleston, SC (USA). Patients. - A total of 135 infants and children noted to have markedly increased total ALP activity. Main Outcome Measures. - Recognition of the disease pathogenesis with appropriate treatment instituted. Results. - Three groups of patients were identified: (1) previously healthy patients who showed additional laboratory evidence of viral and protozoal infection, in whom the ALP isoenzyme pattern reflected the primary target organ(s) of the infection; (2) patients with clinical evidence of failure to thrive due to preexisting disease, along with a superimposed infection (the ALP isoenzyme pattern reflected the specific infection and fractions associated with the primary disease); and (3) patients exhibiting failure to thrive (nonorganic or caloric deficit) who did not show evidence of infection. The total ALP in the third group was lower than in the other groups, was of hepatic and bone origin, and decreased when a positive caloric balance was established. Conclusion. - We examined several mechanisms to explain the hyperphosphatasemia. A perplexing question remains: Will a small group of infants and children respond to infection with this magnitude of ALP activity? Conversely, do all children respond, but a small number fortuitously undergo laboratory measurements that include ALP levels?