Alkaline Phosphatase > 2000 U/L in an Infant With Stool Changes: A Case Report

Transient hyperphosphatasemia (TH) is a benign condition observed among healthy infants and children < 5 years old. It is characterized by an elevation in serum alkaline phosphatase (ALP) in the absence of other signs of organ disease. Prognosis is excellent, and ALP levels stabalize within 4 months. The aim of this case report is to promote broader awareness of TH so further unnecessary workup is avoided. The patient was a 12-month-old girl who presented with pale stools, a single episode of bloody stool, and elevation (incidentally found) in her ALP of 2379 IU/L. A small anal fissure was present, and the remainder of her physical examination was typical. The differential diagnosis included biliary atresia, liver disease, bone disease, and TH. Further testing was typical and included complete blood count (CBC, consisting of hemoglobin, hematocrit, white blood cell count, and platelet count), comprehensive metabolic panel (CMP, consisting of glucose, creatinine, BUN, electrolytes, and liver function markers), calcium, phosphate, parathyroid hormone, gamma-glutamyl transferase, and 25-hydroxy vitamin D. Liver ultrasound was also typical without evidence of biliary atresia. The diagnosis of TH was made. The patient was monitored clinically. Repeat blood work was completed 2 months later, with ALP levels returning to the typical range. Overall, TH is a benign self-limiting condition that can be managed by observation and serial measurement of ALP without further unnecessary investigations.