Since 2015 Asfotase alfa (AA, Strensiq®, Alexion Pharmaceuticals, Inc., Boston, MA, USA), a human recombinant TNAP enzyme replacement therapy, is approved in many countries for long-term enzyme replacement therapy (ERT) in patients with pediatric-onset HPP to treat bone manifestations of the disease [13, 14]. Here, ALPL is linked to hypophosphatasia.