SOX9 and hypophosphatemic rickets, X-linked recessive: Genome-wide association studies have identified genes involved in chondrogenesis, such as EP3000, CREBBP, SOX9, ATF4 and LHX4.45 A limited number of case reports have presented the association of this condition with abnormal skull morphology, especially due to a small posterior fossa in the context of bone disorders such as X-linked recessive hypophosphatemic rickets (OMIM #300554), or its X-linked dominant counterpart (OMIM # 307800).46,47 However, a clear mechanistic association between these conditions has not been accomplished.