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 in OMIM continues to grow. The phenotype–gene relationships are tabulated in OMIM’s Morbid Map of the Human Genome (Morbid Map). Currently, over 6200 phenotypes have been attributed to molecular alterations in over 3900 genes (Figure 1). To enable the discovery of new disease pathways and assist in organization and classification of disease, OMIM groups clinically similar phenotypes with different genetic bases into Phenotypic Series. OMIM currently has over 420 Phenotypic Series comprising over 3500 phenotypes. Several phenotypes reside in more than one series. For example, nine forms of limb-girdle muscular dystrophy are also classified as the less severe manifestation of mutations in the dystroglycanopathy genes (FKRP, POMGNT1, POMT2, etc.).
