Online Mendelian Inheritance in Man (OMIM) is a database that catalogues all the known diseases with a genetic component, and — when possible — links them to the relevant genes in the human genome and provides references for further research and tools for genomic analysis of a catalogued gene. OMIM is one of the databases housed in the U.S. National Center for Biotechnology Information (NCBI) and included in its search menus.
Mendelian Inheritance in Man was started in the early 1960s and is available as a book currently in its 12th edition. The online version, OMIM, has been available since 1987, moved to the World Wide Web by NCBI in 1995, and in 2004 contained more than 15,000 records.
Collection process and use
The information in OMIM was collected and processed from its inception under the leadership of Dr. Victor A. McKusick at Johns Hopkins University, assisted by a team of science writers and editors. Relevant articles are identified, discussed and written up in the relevant entries in the MIM database.
The database has been used as a resource for locating literature relevant to inherited conditions.
The MIM code
Every disease and gene is assigned a six digit number of which the first number classifies the method of inheritance.
If the initial digit is 1, the trait is deemed autosomal dominant; if 2, autosomal recessive; if 3, X-linked. Wherever a trait defined in this dictionary has a MIM number, the number from the 12th edition of MIM, is given in square brackets with or without an asterisk (asterisks indicate that the mode of inheritance is known; a number symbol (#) before an entry number means that the phenotype can be caused by mutation in any of two or more genes) as appropriate e.g., Pelizaeus-Merzbacher disease [MIM #312080] is an X-linked recessive disorder. As per the OMIM website, An asterisk (*) before an entry number indicates a gene.
A number symbol (#) before an entry number indicates that it is a descriptive entry, usually of a phenotype, and does not represent a unique locus. The reason for the use of the number symbol is given in the first paragraph of the entry. Discussion of any gene(s) related to the phenotype resides in another entry(ies) as described in the first paragraph.
A plus sign (+) before an entry number indicates that the entry contains the description of a gene of known sequence and a phenotype.
A percent sign (%) before an entry number indicates that the entry describes a confirmed mendelian phenotype or phenotypic locus for which the underlying molecular basis is not known.
No symbol before an entry number generally indicates a description of a phenotype for which the mendelian basis, although suspected, has not been clearly established or that the separateness of this phenotype from that in another entry is unclear.
A caret (^) before an entry number means the entry no longer exists because it was removed from the database or moved to another entry as indicated. 
Range of MIM codes: Method of inheritance
- 100000–299999: Autosomal loci or phenotypes (created before May 15, 1994)
- 300000–399999: X-linked loci or phenotypes
- 400000–499999: Y-linked loci or phenotypes
- 500000–599999: Mitochondrial loci or phenotypes
- 600000–above : Autosomal loci or phenotypes (created after May 15, 1994)
These codes have been used in the medical literature to provide a unified index to genetic diseases.
- Comparative Toxicogenomics Database, a database that integrates chemicals and genes with human diseases, including OMIM data.
- DECIPHER, a database of chromosomal imbalance and associated phenotype in humans, using Ensembl resources.
- Medical classification
- Mendelian inheritance
- Online Mendelian Inheritance in Animals
- List of OMIM disorder codes
- OMIM home page