There is a strong likelihood that a transversion at the invariant +1 position of the splice donor site would disrupt splicing, as evidenced by previous examples of splice donor site transversions resulting in a disease phenotype (e.g., splice site disruption leading to hereditary thrombocythemia [102], in congenital afibrinogenemia [103], and mutations in CHD7 leading to CHARGE syndrome [104]). This evidence concerns the gene CHD7 and familial thrombocytosis.