GNAS and pseudohypoparathyroidism type 1A: Mutations in GNAS exons that encode the alpha-subunit of the stimulatory G protein (Gαs) lead to Albright Hereditary Osteodystrophy (AHO), which is characterized by brachydactyly, brachymetacarpia, short stature, and frequently subcutaneous ossifications (SCO), i.e. heterotopic bone formation [1]–[4].