Late diagnosis of hypophosphatasia in a case with Unverricht-Lundborg disease

A significant increase in the activity of serum alkaline phosphatase is commonly reported in patients on long-term antiepileptic treatment or after any uncomplicated fracture. We report a case of a 35-year-old male patient on five different anticonvulsant medications for treatment of the rare autosomal recessive neurodegenerative disorder, Unverricht-Lundborg disease. He presented with bilateral metatarsal fractures: however, his serum alkaline phosphatase activity remained below the lower limit of reference interval. Biochemical laboratory investigations revealed a longstanding low serum alkaline phosphatase and raised plasma pyridoxal-5′-phosphate concentration. Sequencing of genomic DNA revealed that he is heterozygous for a mutation in the ALPL gene, which is consistent with the diagnosis of hypophosphatasia.