Infantile hypophosphatasia caused by compound heterozygous variants in the ALPL gene: a case report.

This article reports a case of infantile hypophosphatasia (HPP) due to compound heterozygous alkaline phosphatase-liver/bone/kidney (ALPL) gene mutations, and analyzes its clinical phenotype and genetic characteristics. A retrospective analysis was conducted on the clinical data, genetic testing results, and family history of a male infant with HPP. The infant presented with intrauterine and postpartum growth retardation, respiratory failure, feeding difficulties, vitamin B6-responsive epileptic seizures, bone hypomineralization, hypercalcemia, and very low alkaline phosphatase (ALP). Genetic testing revealed compound heterozygous ALPL mutations: c.533A>G (p.Tyr178Cys) and c.644T>A (p.Ile215Asn), inherited from his father and mother, respectively, both parents being phenotypically normal. The mother had previously terminated a pregnancy due to fetal bone deformity. This case of infantile HPP resulted from compound heterozygous ALPL mutations, with typical clinical features including bone hypomineralization, hypercalcemia, and profoundly low ALP. Without enzyme replacement therapy, the disease is progressing.