In the intricate script of human DNA, OMIM helps us find the typos that change lives.
Explore OMIMImagine a vast library containing the entire collective knowledge of human genetics—a catalog of every gene discovered and every inherited condition linked to our DNA.
This repository exists today as Online Mendelian Inheritance in Man (OMIM), an indispensable digital compass guiding clinicians and researchers through the complex landscape of human genetic variation 1 . For neurologists diagnosing a rare movement disorder, pediatricians evaluating a child with unusual symptoms, or laboratories interpreting genetic test results, OMIM provides the critical bridge between our growing understanding of the human genome and real-world clinical applications 2 .
Total Entries
Gene Entries
Daily Users
The story of OMIM begins not with computer code, but with the printed page. Dr. Victor A. McKusick, often hailed as the "Father of Medical Genetics," recognized the need to catalog all known Mendelian traits and disorders 2 . His seminal work, Mendelian Inheritance in Man, first published in 1966, laid the foundation for what would become OMIM 1 .
Twelve editions published between 1966 and 1998 tracked the rapid advancements in genetic science 1 .
McKusick's catalogs went online in 1987, making them searchable and accessible to researchers worldwide 2 .
First edition of Mendelian Inheritance in Man published by Dr. Victor A. McKusick 1 .
Transition from printed text to dynamic database with online accessibility 2 .
OMIM becomes freely available on the World Wide Web through collaboration between Johns Hopkins University and NCBI 3 .
Curated and updated daily by a dedicated team at Johns Hopkins University School of Medicine 4 .
At its core, OMIM is a comprehensively curated compilation of human genes and genetic phenotypes—the observable characteristics resulting from genetic variation 1 . What sets OMIM apart from simple repositories is its expert synthesis of complex scientific literature into coherent, structured entries that illuminate the relationships between genes and conditions 1 .
Each entry in OMIM is assigned a unique, stable six-digit identifier known as a MIM number 1 . These numbers are preceded by specific symbols that immediately convey the nature of the entry to experts in the field:
| Symbol | Entry Type | Description | Example |
|---|---|---|---|
| * | Gene | A known gene with established sequence | 100640 (ADRB2 gene for beta-2 adrenergic receptor) |
| # | Phenotype | Descriptive entry for a disorder with known molecular basis | #143100 (Huntington disease) |
| % | Phenotype | Mendelian disorder with unknown molecular basis | %236200 (Autoimmune polyendocrine syndrome) |
| + | Combined | Entry describing both a gene and related phenotype | +162240 (CRYGA gene and cataract) |
Include comprehensive information on gene structure, function, expression patterns, and known variants 1 .
One of OMIM's most powerful features is the Phenotypic Series—collections of clinically similar disorders caused by variants in different genes 1 2 . Viewing these series side-by-side reveals fascinating patterns in human genetics.
PS118220 - Group of inherited neurological disorders affecting peripheral nerves.
PS303350 - Group of inherited disorders characterized by progressive lower limb weakness and spasticity.
PS164400 - Group of inherited brain disorders affecting coordination and balance.
To understand how OMIM fuels scientific advancement, consider a fictional but representative research scenario involving a team investigating a rare neurological disorder.
Researchers begin with a patient presenting with a distinctive combination of symptoms: progressive muscle weakness, unusual eye movement abnormalities, and specific changes on brain MRI.
The team suspects a genetic cause, likely with autosomal recessive inheritance based on family history.
| Gene | Chromosomal Location | Known Function | Similar Disorders | Inheritance Pattern |
|---|---|---|---|---|
| Novel Gene | 2q24.3 | Mitochondrial protein synthesis | Leigh syndrome, COX deficiency | Autosomal recessive |
| AFG3L2 | 18p11.21 | Mitochondrial protease | Spinocerebellar ataxia type 28 | Autosomal dominant |
| SPG7 | 16q24.3 | Mitochondrial metalloprotease | Hereditary spastic paraplegia | Autosomal recessive |
The team's discovery, supported by OMIM's structured knowledge, represents a significant advance. They establish a new gene-disease relationship, enabling genetic testing for other families with similar symptoms and contributing to our understanding of mitochondrial biology.
OMIM serves as a central hub connecting researchers to a network of specialized databases and analytical tools. These resources form an essential toolkit for modern genetic investigation:
| Resource Category | Examples | Primary Function | Research Application |
|---|---|---|---|
| Genome Browsers | Ensembl, UCSC Genome Browser | Genomic context and regulation | Viewing gene location, regulatory elements |
| Variant Databases | ClinVar, dbSNP, gnomAD | Pathogenic and population variants | Assessing variant frequency and pathogenicity |
| Protein Resources | UniProt, HPRD | Protein structure and function | Understanding molecular consequences |
| Model Organisms | MGI, FlyBase, WormBase | Animal model information | Exploring gene function in other species |
| Clinical Resources | ClinGen, GeneReviews, ClinicalTrials.gov | Patient care and trials | Translating findings to clinical practice |
These interconnected resources create a research ecosystem that accelerates discovery 1 . When a clinician identifies a novel gene variant in a patient with an unusual genetic syndrome, they can use OMIM to access relevant literature, then follow links to ClinVar to see if the variant has been reported previously, check gnomAD for its frequency in general populations, examine UniProt for the variant's location within the protein structure, and review MGI for mouse models with mutations in the same gene 1 .
OMIM's impact extends far beyond a simple reference tool—it plays a fundamental role in how we classify, understand, and ultimately treat genetic conditions.
One of OMIM's most significant contributions is in the nosology (classification and naming) of genetic diseases 2 .
This careful curation creates a stable foundation for the entire field. While disease names may evolve as understanding deepens, the MIM number remains constant, providing a fixed reference point that unifies clinical names and aliases 2 .
OMIM plays an increasingly vital role in clinical diagnostics, particularly as next-generation sequencing becomes more common in medical practice 2 .
For rare neurological disorders, which represent a substantial portion of Mendelian conditions, OMIM has become an indispensable tool for neurologists seeking to understand the molecular basis of their patients' conditions 2 .
As Dr. McKusick himself recognized, cataloging human genes and genetic disorders is not merely an academic exercise—it is fundamental to understanding human biology and developing treatments for the thousands of conditions that trace back to our DNA 2 . In the intricate script of the human genome, OMIM provides the critical annotations that help us read between the lines.