Infantile hypophosphatasia without bone deformities presenting with severe pyridoxine-resistant seizures

• The precise metabolic cause of the seizures in HPP remains unknown.
• A curative therapy for the epilepsy of HPP is still not available.
• The treatment in HPP with only seizures should be enzyme replacement therapy.

An infant carrying a heterozygous c.43_46delACTA and a heterozygous c.668 G>A mutation in the ALPL gene with hypophosphatasia in the absence of bone deformities presented with therapy-resistant seizures. Pyridoxal phosphate was extremely high in CSF and plasma. Pyridoxine treatment had only a transient effect and the severe encephalopathy was fatal. Repeated brain MRIs showed progressive cerebral damage. The precise metabolic cause of the seizures remains unknown and pyridoxine treatment apparently does not cure the epilepsy.