The process of HO in rare genetic disorders such as AHO/PHP/POH and the pathophysiological mechanisms by which alterations of PTH/PTHrP-Gsα-cAMP signaling led to ectopic bone formation are not fully understood; to date, investigations have been mainly conducted in mouse models (26, 31, 32). Here, PTHLH is linked to pseudohypoparathyroidism type 1A.