OMIM evaluates reports of new phenotypes in the context of those present in the catalog. Reports describing a purportedly novel phenotype are evaluated to answer the following questions: How many patients have been described in how many reports? What shared features actually define the phenotype, and how thorough are the clinical descriptions? Does this constellation of features represent a new entity? Do the different features of a disorder constitute clinical variability of a single disorder or define separate disorders? Have the same or similar features been described under a different name? Is the phenotype similar to others in OMIM? Can the phenotype be classified with any other disorders? Answering these questions must also take into account the views and possible disagreements in the genetics community as well as published nosologies. Finally, because the definition of a phenotype (constellation of features) as a genetic entity is an evolving process, the naming of a disorder in OMIM may change over time, but a MIM number remains a stable identifier. OMIM splits phenotypes by their molecular basis. Individual members of a genetically heterogeneous
