One FGFR3 mutation (c.1620C>A p.N540K), one likely pathogenic GNAS mutation (c.2288C>T p.A763V), and one TRPS1 mutation (c.2527_c.2528dupTA p.S843fsX72) was identified in three pedigrees with hypochondroplasia, pseudohypoparathyroidism Ia (PHP-Ia), and trichorhinophalangeal syndrome type I (TRPS I). Here, GNAS is linked to trichorhinophalangeal syndrome type I.