Objective
To describe the prevalence and clinical characteristics of transient hyperphosphatasemia (TH) in a cohort of healthy infants and toddlers.
Patients and Methods
We performed a secondary data analysis of children enrolled in a study examining the epidemiology of vitamin D deficiency among healthy infants and toddlers. Children aged 8 to 24 months were enrolled at well-child visits conducted from 2005 - 2007 in an urban primary care pediatric clinic. Children with a chronic disease or using medications known to affect bone metabolism were excluded. At enrollment, we collected data regarding child age, gender, height, and weight; and maternal race/ethnicity. We measured serum levels of alkaline phosphatase, 25-hydroxyvitamin D, parathyroid hormone (PTH), calcium, magnesium and phosphorus. We divided participants into three categories, based on serum AP levels at enrollment: normal (AP 110 to 400 U/L), intermediate (AP >400 to 1000 U/L), and TH (AP >1000 U/L). We used the Fisher exact test and analysis of variance to evaluate differences in clinical characteristics among the three groups.
Results
Nine of 316 children (2.8%) had an AP > 1000 U/L (mean 2165 U/L, range 1006 to 4293 U/L). Sixteen children (5.1%) had an intermediate serum AP (mean 544 U/L, range 423 to 835 U/L). Mean weight-for-age z-score, length-for-age z-score and weight-for-length z-scores were similar across all three AP groups. Compared to the 291 children without TH, children in the intermediate AP and TH groups had similar mean serum levels of 25-hydroxyvitamin D, PTH, calcium, magnesium, and phosphorus.
Conclusions
TH appears to be a relatively common condition among healthy infants and toddlers. TH was not associated with anthropometric measures, vitamin D status, PTH, or serum minerals. Recognition of this benign condition is important to avoid unnecessary investigations.