At the time of established HPP diagnosis the following supportive diagnostic findings have been documented: 96% (48/50) showed a documented low AP activity, 88% (44/50) typical HPP-associated symptoms, 58% (29/50) elevated levels of AP substrates (PLP and PEA), 48% (24/50) radiological abnormalities, 18% (9/50) genetic testing of the ALPL gene as performed at the time of diagnosis and in 12% (6/50) an HPP positive family history was known. Here, ALPL is linked to hypophosphatasia.