Abstract
This case report is a neonate with hypophosphatasia（HPP）. She has respiratory problems immediately after birth, and developed vitamin B6-dependent seizures from day 13. She was diagnosed with severe perinatal hypophosphatasia because she had significant low serum ALP level, thinning of ribs and rickets-like changes in the limbs.
Seizures and abnormal brain waves rapidly disappeared after intravenous administration of pyridoxine. She received ALP enzyme replacement therapy（ERT）from day 22. Respiratory failure improved and she could be weaned off ventilator at 2 months of age. In addition, bone mineralization improved and rickets-like changes mostly disappeared at 3 months of age. She left the hospital at 5 months of age. Most of the perinatal severe HPP have reported homozygous mutations in the responsible gene. But she had a heterozygous mutation in c.1559delT and should be noted. Although the clinical course of HPP can be predicted to some extent from the ALPL variants, the severity of symptoms may differ even in patients with the same variants.
Additional tests may identify other genetic modifiers. Future physical growth and development, and dental follow-up are important for evaluating the relationship between genotype and clinical course.
