GNAS and progressive osseous heteroplasia: Defects of the GNAS gene have been associated with different phenotypes such as pseudohypoparathyroidism Ia, Ib, and Ic (PHP-Ia, -Ib, -Ic), pseudopseudohypoparathyroidism (PPHP), progressive osseous heteroplasia (POH), and osteoma cutis (OC) [3].