Transient hyperphosphatasemia in pediatric renal transplant patients--is there a need for concern and when?

TH of infancy and early childhood is characterized by transiently increased S-ALP, predominantly its bone or liver isoforms. There are neither signs of metabolic bone disease or hepatopathy corresponding to the increased S-ALP, nor a common underlying/triggering disease. TH may also occur in children post-renal Tx, which may raise significant concerns and anxiety. We describe four patients aged 2.8-7 yr in whom the TH occurred at 11-34 (median = 28) months after Tx and lasted from 40 to 105 (median = 63) days. No obvious cause/trigger of TH could be found; the clinical status and bone turnover were not altered. In cases of TH post-Tx, we recommend the evaluation of basic biochemical indices and wrist X-ray. If these results are normal, TH is most likely the diagnosis and the S-ALP can be monitored over the next three months without further testing. In patients with persisting TH for more than three months and/or in children with pre-existing or suspected metabolic bone disease, further evaluation may be indicated. In conclusion, TH is a benign disorder in patients post-Tx. Detailed investigation including bone biopsy is only indicated in patients with persisting TH.