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MYH9 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

MYH9 gene

MYH9 encodes the myosin‑9 protein, a subunit of myosin IIA, and mutations cause a disorder characterized by bleeding problems, hearing loss, kidney disease, and cataracts.

Normal Function

The MYH9 gene provides instructions for making a protein called myosin‑9. This protein is one part (subunit) of the myosin IIA protein.

There are three forms of myosin II, called myosin IIA, myosin IIB and myosin IIC. They play roles in cell movement (cell motility); maintenance of cell shape; and cytokinesis, which is the step in cell division when the fluid surrounding the nucleus (the cytoplasm) divides to form two separate cells. While some cells use more than one type of myosin II, certain blood cells such as platelets and white blood cells (leukocytes) use only myosin IIA.

Each type of myosin II protein consists of two heavy chains and four light chains. The heavy chains each have two parts: a head region and a tail region. The head region interacts with actin, a protein that is important for cell movement and shape. The long tail region interacts with other proteins, including the tail regions of other myosin proteins.

Health Conditions Related to Genetic Changes

MYH9‑related disorder

More than 45 mutations in the MYH9 gene have been found to cause MYH9‑related disorder. This disorder is characterized by bleeding problems, hearing loss, kidney (renal) disease, and clouding of the lens of the eyes (cataracts). Most of the mutations that cause this condition change single protein building blocks (amino acids) in the myosin‑9 protein. Mutations that are located near the head of the myosin protein tend to lead to a more severe disorder than mutations that are located toward the tail of the protein. Recurring mutations involving the amino acid arginine at position 702 in the protein tend to result in many problems, including a severely reduced amount of platelets (thrombocytopenia), early‑onset renal disease, and hearing loss in infancy.

Mutations in the MYH9 gene lead to the production of a nonfunctional protein. A nonfunctional myosin‑9 protein cannot properly interact with other subunits to form myosin IIA. Platelets, which only express myosin IIA, are most affected by a lack of functional myosin‑9, accounting for the thrombocytopenia seen in all individuals with MYH9‑related disorder.

Nonsyndromic hearing loss

MedlinePlus Genetics provides information about Nonsyndromic hearing loss.

Other Names for This Gene

  • cellular myosin heavy chain, type A
  • MYH9_HUMAN
  • myosin heavy chain, non‑muscle IIa
  • myosin, heavy chain 9, non‑muscle
  • myosin‑9
  • NMHC‑II‑A
  • NMMHC II‑a
  • NMMHC‑A
  • NMMHC‑IIA
  • NMMHCA
  • non‑muscle myosin heavy chain A
  • non‑muscle myosin heavy chain IIa
  • nonmuscle myosin heavy chain II‑A

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

  • Tests of MYH9

Scientific Articles on PubMed

  • PubMed

Catalog of Genes and Diseases from OMIM

  • MYOSIN, HEAVY CHAIN 9, NONMUSCLE; MYH9

Gene and Variant Databases

  • NCBI Gene
  • ClinVar

References

  • Althaus K, Greinacher A. MYH9‑related platelet disorders. Semin Thromb Hemost. 2009 Mar;35(2):189‑203. doi: 10.1055/s-0029-1220327. Epub 2009 Apr 30. Citation on PubMed
  • Kunishima S, Saito H. Advances in the understanding of MYH9 disorders. Curr Opin Hematol. 2010 Sep;17(5):405‑10. doi: 10.1097/MOH.0b013e32833c069c. Citation on PubMed
  • Sekine T, Konno M, Sasaki S, Moritani S, Miura T, Wong WS, Nishio H, Nishiguchi T, Ohuchi MY, Tsuchiya S, Matsuyama T, Kanegane H, Ida K, Miura K, Harita Y, Hattori M, Horita S, Igarashi T, Saito H, Kunishima S. Patients with Epstein‑Fechtner syndromes owing to MYH9 R702 mutations develop progressive proteinuric renal disease. Kidney Int. 2010 Jul;78(2):207‑14. doi: 10.1038/ki.2010.21. Epub 2010 Mar 3. Citation on PubMed

Genomic Location

The MYH9 gene is found on chromosome 22.

Frequently Asked Questions

Patients often experience easy bruising, prolonged bleeding after cuts or dental work, nosebleeds, and, in severe cases, spontaneous internal bleeding such as gastrointestinal or intracranial hemorrhage. Platelet function tests typically show low platelet count or dysfunctional platelets.
Diagnosis involves a combination of clinical evaluation, platelet function tests, and DNA sequencing of the MYH9 gene. A positive genetic test confirms the diagnosis and helps guide surveillance for associated complications.
Management focuses on preventing and controlling bleeding: antifibrinolytic agents (e.g., tranexamic acid), platelet transfusions for severe bleeding, and careful use of anticoagulants. Avoiding medications that impair platelet function (e.g., NSAIDs) is also advised.
Cataracts in MYH9 patients often develop in adolescence or early adulthood. Surgery is considered when visual acuity drops below 20/40 or when cataracts interfere with daily activities. Pre‑operative evaluation should include assessment of platelet function to minimize surgical bleeding risk.
Hearing loss usually begins in early childhood and progresses over time. Regular audiologic evaluations are recommended, and hearing aids or cochlear implants may be considered when thresholds worsen. Early intervention can improve communication outcomes.
Kidney involvement can range from mild proteinuria to progressive renal failure. Annual urinalysis and serum creatinine tests are advised, with more frequent monitoring if proteinuria is detected. Early referral to a nephrologist is important for managing blood pressure and proteinuria.
MYH9 mutations are inherited in an autosomal dominant manner, meaning a single copy of the mutated gene can cause disease. If a parent carries the mutation, each child has a 50% chance of inheriting it. Genetic counseling is recommended for family planning.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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