Bone Abstracts

Objectives: To evaluate the frequency of low serum alkaline phosphatase (ALP) activities in patients referred to a tertiary children’s hospital. Another item was to explore potentially missed diagnoses and to evaluate the role of laboratory screening for hypophosphatasia.

Study design: A retrospective evaluation over an 6-year period (between December 2010 and December 2016) carried out to identify children and adolescents, referred to Anna Meyer Children’s University Hospital in Florence, younger than 16 years old with low ALP activity for sex, age, and pubertal stage.

Results: Of 16.896 patients and 26.724 analyzed samples in our Hospital, 523 (3.1%) patients had low ALP activities. Most of these had transient hypophosphatasemia. However, 32 (6.1%) patients were identified as study-positive for persistent low ALP activity. Of these, four patients had been evaluated for rheumatologic problems, 12 patients with orthopaedic problems (unexplained fractures), two patients for endocrine problems (short stature), two patients for respiratory failure in the first years of age, three patients for neurosurgical problems (craniosynostosis and intracranial hypertension), one patient nephrology problems, two patients poor feeding and failure to thrive, and six patients for neurological problems (recurrent seizures). No patient had been recalled for such low values in suspicion of hypophosphatasia.

Conclusions: Missed diagnoses of hypophosphatasia are frequent in a tertiary children’s Hospital. However, patients with persistently low ALP activity require clinical, biochemical, and radiological assessment for hypophosphatasia, even in the absence of obvious clinical symptoms. Our data is important also because early detection of cases of hypophosphatasia, with the availability of enzyme replacement therapy, can be life-saving or avoid years of undiagnosed morbidity. In our patients, a retesting with pyridoxal-5’-phosphate and phosphoethanolamine concentrations and subsequently for ALPL gene mutations will be necessary for confirm the suspicion of hypophosphatasia.

Disclosure: The authors declared no competing interests.