TRANSIENT HYPERPHOSPHATASEMIA OF INFANCY AND CHILDHOOD - A STUDY OF SERUM ALKALINE-PHOSPHATASE BY ELECTROFOCUSING TECHNIQUES

Objective.-To evaluate serum alkaline phosphatase (ALP) isoenzymes, us ing a sensitive electrofocusing technique, in transient hyperphosphata semia of infancy and childhood. Design.-Randomized study of infants an d children who provided serum samples when an unusual magnitude of tot al ALP activity was noted. Setting.-Reference enzyme laboratories in G orizia and Bergamo (Italy) and in Charleston, SC (USA). Patients.-A to tal of 135 infants and children noted to have markedly increased total ALP activity. Main Outcome Measures.-Recognition of the disease patho genesis with appropriate treatment instituted. Results.-Three groups o f patients were identified: (1) previously healthy patients who showed additional laboratory evidence of viral and protozoal infection, in w hom the ALP isoenzyme pattern reflected the primary target organ(s) of the infection; (2) patients with clinical evidence of failure to thri ve due to preexisting disease, along with a superimposed infection (th e ALP isoenzyme pattern reflected the specific infection and fractions associated with the primary disease); and (3) patients exhibiting fai lure to thrive (nonorganic or caloric deficit) who did not show eviden ce of infection. The total ALP in the third group was lower than in th e other groups, was of hepatic and bone origin, and decreased when a p ositive caloric balance was established. Conclusion.-We examined sever al mechanisms to explain the hyperphosphatasemia. A perplexing questio n remains: Will a small group of infants and children respond to infec tion with this magnitude of ALP activity? Conversely, do all children respond, but a small number fortuitously undergo laboratory measuremen ts that include ALP levels?