A Diagnostic Algorithm for Children with Low Alkaline Phosphatase Activities: Lessons Learned from Laboratory Screening for Hypophosphatasia.

OBJECTIVES: To explore the role of laboratory screening for hypophosphatasia and propose a diagnostic pathway for children with low serum alkaline phosphatase (ALP) activities. STUDY DESIGN: A retrospective hospital-based study over an 8-year period was conducted to identify children younger than 16 years of age with low ALP activity (<100 U/L). Study-positive patients were contacted for repeat sampling, and those with persistently low ALP had plasma pyridoxal-5'-phosphate and urinary phosphoethanolamine measured. RESULTS: Of 323 064 analyzed samples, 1526 had ALP activities <100 U/L. Most patients had transient hypophosphatasemia. Of 50 patients with last-recorded ALP <100 U/L, 32 were excluded given previous ALP >100 U/L. Eighteen were identified as study-positive. Of the 15 surviving children, 13 were traceable. Four had persistently low ALP activity on retesting, of whom 2 had raised pyridoxal-5'-phosphate and phosphoethanolamine concentrations and were subsequently tested for ALPL gene mutations; a 4-year-old asymptomatic girl with a novel homozygous ALPL missense mutation and a 23-year-old female with a heterozygous mutation. There was significant overlap in ALP activities between study-positive and 11 current patients with hypophosphatasia. We propose a diagnostic algorithm for children with low ALP activities based on clinical and biochemical variables. CONCLUSIONS: Patients with persistently low ALP activity require further clinical, biochemical, and radiological assessment for hypophosphatasia, even in the absence of clinical symptoms. The proposed diagnostic algorithm for children with low ALP will facilitate early detection of cases of hypophosphatasia, which, with the availability of enzyme replacement for hypophosphatasia, can be life-saving or avoid years of undiagnosed morbidity.

Use of Vandetanib in Metastatic Medullary Carcinoma of Thyroid in a Pediatric Patient With Multiple Endocrine Neoplasia 2B.

We describe a child with advanced, metastatic, inoperable medullary carcinoma of thyroid associated with multiple endocrine neoplasia 2B and rearranged during transfection mutation with a positive response to vandetanib treatment. He responded well with a fall in calcitonin levels and a reduction in size of the thyroid malignancy, lymph nodes, and pulmonary metastases. He has been on vandetanib for 4 years with good clinical and biochemical response. Vandetanib has a role in the treatment of patients including children with inoperable locally advanced and metastatic medullary carcinoma of thyroid. More information is needed on its use in children and long-term outcome.