Throughout its history, the primary mission of OMIM has been to collect and curate knowledge on human genes and genetic disorders and traits. OMIM currently has over 24 600 entries describing over 16 000 genes and 8600 phenotypes (Table 1). All entries in OMIM are given unique and stable MIM numbers. Genes and phenotypes are described in separate entries and Allelic Variants are included in the gene entries. MIM number prefixes aid in distinguishing the content of the entry: * (asterisk) denotes a gene entry; + (plus sign) denotes an entry describing both a gene and phenotype; # (number sign) denotes a phenotype with a known molecular basis; % and null denote phenotypes with varying levels of supporting information for familial occurrence. Although there are a number of phenotypes in OMIM that are not ascribed to mutations in specific genes, these do not represent the totality of Mendelian disease. High-throughput and lower-cost sequencing has enabled the discovery of many previously undescribed Mendelian phenotypes. Since 2014, OMIM has added approximately 300 new phenotypes per year, and the total number of phenotypes
