OMIM Frequently Asked Questions (FAQs)

What is OMIM?

Online Mendelian Inheritance in Man (OMIM®) is a continuously updated catalog of human genes and genetic disorders and traits, with particular focus on the molecular relationship between genetic variation and phenotypic expression. It is thus considered to be a phenotypic companion to the Human Genome Project. OMIM is a continuation of Dr. Victor A. McKusick's Mendelian Inheritance in Man, which was published through 12 editions, the last in 1998. OMIM is currently biocurated at the McKusick-Nathans Institute of Genetic Medicine, The Johns Hopkins University School of Medicine.

What numbering system is used in the OMIM database?

Each OMIM entry is given a unique six-digit number as summarized below:

1----- (100000- ) 2----- (200000- ) Autosomal loci or phenotypes (entries created before May 15, 1994)

3----- (300000- ) X-linked loci or phenotypes

4----- (400000- ) Y-linked loci or phenotypes

5----- (500000- ) Mitochondrial loci or phenotypes

6----- (600000- ) Autosomal loci or phenotypes (entries created after May 15, 1994)

Allelic variants (mutations; see 1.4) are designated by the MIM number of the entry, followed by a decimal point and a unique 4-digit variant number. For example, allelic variants in the factor IX gene (300746) are numbered 300746.0001 through 300746.0101.

What do the symbols preceding a MIM number represent?

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.

See also the description of symbols used in the disorder column of the OMIM Gene Map and Morbid Map.

How are mutations cataloged in OMIM?

Mutations are cataloged in OMIM in the Allelic Variants section of gene entries (see 1.2). For most genes, only selected mutations are included. Criteria for inclusion include the first mutation to be discovered, high population frequency, distinctive phenotype, historic significance, unusual mechanism of mutation, unusual pathogenetic mechanism, and distinctive inheritance (e.g., dominant with some mutations, recessive with other mutations in the same gene). Most of the allelic variants represent disease-causing mutations. A few polymorphisms are included, many of which show a positive correlation with particular common disorders.

These criteria are spelled out in more detail in:

Amberger, J. et al. Nucleic Acids Research 43:D789, 2015 (PMID 25428349).

What is the OMIM Gene Map and Morbid Map?

The OMIM Gene Map and Morbid Map present the cytogenetic locations of genes and disorders, respectively, that are described in OMIM. Only OMIM entries for which a cytogenetic location has been published in the cited references are represented in the Gene Map and Morbid Map.

The OMIM Gene Map can be searched by gene symbol (e.g., "SOD1"), chromosomal location (e.g., "5", "1pter", "Xq" ), or by disorder keyword (e.g., "alzheimer").

What do brackets [ ], braces { }, a question mark (?), and the numbers (1)(2)(3)(4) mean in the Disorder column of the Gene Map?

Brackets, "[ ]", indicate "nondiseases," mainly genetic variations that lead to apparently abnormal laboratory test values (e.g., dysalbuminemic euthyroidal hyperthyroxinemia).

Braces, "{ }", indicate mutations that contribute to susceptibility to multifactorial disorders (e.g., diabetes, asthma) or to susceptibility to infection (e.g., malaria).

A question mark, "?", before the phenotype name indicates that the relationship between the phenotype and gene is provisional. More details about this relationship are provided in the comment field of the map and in the gene and phenotype OMIM entries.

The number in parentheses after the name of each disorder indicates the following: (1) the disorder was positioned by mapping of the wildtype gene; (2) the disease phenotype itself was mapped; (3) the molecular basis of the disorder is known; (4) the disorder is a chromosome deletion or duplication syndrome. Move the cursor over the number to display this information.

Can I suggest the addition of a reference to an OMIM record, or make other comments?

Please use the form available at the Contact Us tab at the top of the page.

How should I cite OMIM?

It is usually most appropriate to cite the actual journal article for the data of interest.

Citing OMIM as a whole:

Online Mendelian Inheritance in Man, OMIM®. McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University (Baltimore, MD), {date}. World Wide Web URL:

Citing a specific entry in OMIM:

Online Mendelian Inheritance in Man, OMIM®. Johns Hopkins University, Baltimore, MD. MIM Number: {MIM number}: {Date last edited}: . World Wide Web URL:

Citing an OMIM entry for personal communication:

{Authors};{Date}. Personal Communication in OMIM® Online Mendelian Inheritance in Man. MIM Number: {MIM number} Johns Hopkins University, Baltimore, MD. World Wide Web URL:

Citing the printed version of MIM:

McKusick, V.A.: Mendelian Inheritance in Man. A Catalog of Human Genes and Genetic Disorders. Baltimore: Johns Hopkins University Press, 1998 (12th edition).

What are the software requirements for can be optimally viewed using recent versions of Firefox and Google Chrome, and Internet Explorer 9.0+ on Microsoft Windows; recent versions of Firefox, Google Chrome and Safari on Mac OS X; and a recent version of Firefox on Linux.

How is OMIM funded?

OMIM curation and updating is funded by a grant from the National Human Genome Research Institute (NHGRI) [1U41HG006627]. Initial development of the website was supported by Johns Hopkins Medicine and a grant from the Maryland Department of Health and Mental Hygiene. OMIM is hosted at University of California Santa Cruz (UCSC) Genome Bioinformatics.

Tutorials and other guides for using OMIM.

A quick reference overview and guide (PDF).

Recent publications:

Amberger JS, Bocchini CA, Schiettecatte F, Scott AF, Hamosh A. Online Mendelian Inheritance in Man (OMIM®), an online catalog of human genes and genetic disorders. Nucleic Acids Res. 2015 Jan;43(Database issue):D789-98. PMID: 25428349. (View PDF)
Amberger J, Bocchini C, Hamosh A. A new face and new challenges for Online Mendelian Inheritance in Man (OMIM). Hum Mutat. 2011 May;32(5):564-7. PMID: 21472891. (View PDF)

Where can I access OMIM's website?

OMIM's primary website is available at A mirror site is available at

What reference assembly does OMIM use for the genomic coordinates?

OMIM uses genomic reference build GRCh38 available at

If you wish to get genomic coordinates for GRCh37 /hg19, that data is available from NCBI at

What is a Phenotypic Series?

A Phenotypic Series is a tabular view of genetic heterogeneity of similar phenotypes across the genome. The link is available under the Phenotype-Gene mini-table in many phenotype entries. A list of disorders with a phenotypic series is available here.

What is MIMMatch?

MIMmatch is a way to follow OMIM entries that interest you and to find other researchers who may share interest in the same entries. By registering as a MIMmatch user, you will be able to receive alerts about updates to your genes and diseases of interest. In addition, you may choose to share your name with other MIMmatch registrants. Your name will appear only to other MIMmatch users and only on those entries you designate.

A bonus to all MIMmatch users is the option to sign up for updates on new gene-phenotype relationships.

Your information WILL NOT be shared with any third party, and you will receive no more than one e-mail notification per day.