A patient with hypophosphatemic rickets and ossification of posterior longitudinal ligament caused by a novel homozygous mutation in ENPP1 gene

► A novel mutation in ENPP1 gene was found in a patient with hypophosphatemic rickets. ► This mutation caused skipping of exon 21 and a premature stop codon in exon 22. ► She also showed widespread ossification of posterior longitudinal ligament. ► Enpp1 knockout mouse is a model of ossification of posterior longitudinal ligament. ► This case shows the role of ENPP1 in phosphate metabolism and ectopic ossification.