Understanding May-Hegglin Anomaly: Symptoms, Causes, and Care
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
May-Hegglin anomaly is a rare inherited genetic disorder in which the body makes abnormally large platelets and too few platelets. It is caused by a change in the MYH9 gene. Many people have no symptoms or only mild ones, but the condition can raise the risk of bruising and bleeding, especially after an injury or surgery [1].
Quick Answer: What is May-Hegglin anomaly?
May-Hegglin anomaly is a rare genetic disorder in which the body makes abnormally large platelets and too few of them, caused by an inherited change in the MYH9 gene. Many people have no symptoms, while others bruise easily or have nosebleeds or heavy bleeding. Most people need no treatment, but providers take extra precautions before procedures. [1]
What the research says
It can be mistaken for immune thrombocytopenia (ITP). In a prospective study in China, 42 patients with persistent, unexplained low platelets were screened using platelet size thresholds (mean platelet volume of 14.55 fL or higher, platelet-large cell ratio of 58% or higher, or giant platelets seen on a blood smear); 7 of them (16.7%) were diagnosed with MYH9-related disease, all within 1 month, which avoided unnecessary ITP treatment (Chen et al., Res Pract Thromb Haemost, 2026 [2]).
May-Hegglin anomaly sits within a wider MYH9-related disease family that can affect more than platelets. In a Japanese study that sequenced 15,684 people with hearing loss, 24 patients from 18 families had MYH9-associated hearing loss, and some had rapid deterioration of about 50 dB within 5 years; the authors note that MYH9-related disease, which includes May-Hegglin anomaly, Epstein, Fechtner, and Sebastian syndromes, can also involve hearing loss, kidney inflammation, and cataracts (Goto et al., Genes, 2026 [3]).
What Is May-Hegglin Anomaly?
May-Hegglin anomaly is a rare genetic disorder where your body makes abnormally large platelets and too few platelets. Platelets are blood components that help form clots to stop bleeding when you are injured. You are born with the genetic change, which may cause you to bleed or bruise more easily than someone without the disorder, and you may be more likely to lose a lot of blood after major surgery. On the other hand, many people with the condition do not have symptoms or major problems at all [1].
Whether or not you have symptoms, it is important to know if you have it, so that you and your providers can take steps to reduce your risk of injury or blood loss [1].
May-Hegglin anomaly is one of several MYH9-related disorders, all of which involve a mutation in the MYH9 gene. The other three are Epstein syndrome, Fechtner syndrome, and Sebastian syndrome, and because they share the same cause, these names may eventually fade into the single term “MYH9-related disorder” [1].
What is the diagnostic triad of May-Hegglin anomaly?
The diagnostic triad of May-Hegglin anomaly is giant platelets, a low platelet count and Döhle bodies. Together they help providers distinguish it from other disorders that cause abnormal platelets [1]:
Feature | Description |
Macrothrombocytopenia | Abnormally large platelets. |
Thrombocytopenia | A low platelet count. Fewer than 150,000 platelets per microliter of blood is considered low, and in this condition counts range from about 40,000 to 80,000 up to normal values. |
Döhle bodies | Small rod-shaped structures inside leukocytes, a type of white blood cell. |
The triad of giant platelets, a low platelet count, and Döhle bodies defines May-Hegglin anomaly.
What are the symptoms and bleeding risks of May-Hegglin anomaly?
Many people with May-Hegglin anomaly have enough healthy platelets to avoid bleeding symptoms, while others may bruise or bleed easily. If you do have symptoms, they will likely depend on how low your platelet count is. Signs and symptoms may include [1]:
Easy bruising and bleeding.
Frequent nosebleeds (epistaxis).
Bleeding gums.
Heavy periods (menorrhagia).
Red, purple, or brown spots on your skin (purpura).
Heavy bleeding after surgery, a dental procedure, or delivering a baby.
Easy bruising, nosebleeds, bleeding gums, and heavy periods are common signs of a low platelet count.
What causes May-Hegglin anomaly, and how is it inherited?
With May-Hegglin anomaly, you usually inherit a mutation in your MYH9 gene from one of your biological parents, although in some people the change appears for the first time (a new, or de novo, variant). The mutation causes problems with how platelets form, so they are too large and unusually shaped, and it also causes a low platelet count that may make you bruise or bleed easily. The condition is inherited in an autosomal dominant pattern, which means you only need one copy of the mutated gene to have the disorder [1].
You cannot prevent May-Hegglin anomaly, but if you plan to have biological children it may be a good idea to speak with a genetic counselor. If you or your partner has the condition, there is a 50% chance your child will be born with it too, and a genetic counselor can help you assess the risks and your options [1].
How is May-Hegglin anomaly diagnosed and tested?
Most people do not realize they have May-Hegglin anomaly until a blood test done for an unrelated reason, such as routine blood work during pregnancy, shows a low platelet count and giant platelets. Because the condition is so rare, providers do not often suspect it at first and will likely need to rule out several other conditions that affect platelets before making a diagnosis [1].
Test | Purpose |
Complete blood count (CBC) | Shows whether your platelet count is low. |
Peripheral blood smear | Shows whether you have large platelets, and lets providers look for Döhle bodies in your leukocytes. |
Genetic testing | Shows whether you have a mutation in the MYH9 gene. |
Your provider may also recognize other signs of low platelets, such as an increased bleeding time [1].
How is May-Hegglin anomaly managed with lifestyle adjustments?
Most people with May-Hegglin anomaly do not have symptoms serious enough to need treatment. Still, your provider may need to take extra precautions to prevent serious blood loss after surgery, such as giving you desmopressin by IV or a platelet transfusion before a medical procedure. You may also need a platelet transfusion to restore your levels after an emergency blood loss [1].
If you are pregnant, you may need additional monitoring. Most people with May-Hegglin anomaly deliver healthy babies without complications, but any condition that raises the chance of bleeding poses risks, so your pregnancy provider will advise you on how to protect you and your baby [1].
Self-Care and Prevention
One of the best things you can do is talk with your healthcare provider about how to manage the condition. Be informed about [1]:
Medications: know which medications may interfere with your platelets so you can avoid them or take them in safe doses.
Dental care: good oral hygiene can help prevent bleeding gums.
Activities that can lead to injury: you may need to avoid, or take precautions with, activities where it is easy to get hurt, such as contact sports.
Pregnancy risks: work closely with your pregnancy provider to monitor your health.
Management focuses on safety around procedures, preventing injury, and monitoring during pregnancy.
What is the outlook for May-Hegglin anomaly?
May-Hegglin anomaly is a lifelong condition, but for most people it does not interfere with daily life. Many people have no symptoms or only mild ones, and if you do have a low platelet count, your provider can recommend ways to manage blood loss if you are injured [1]. Because the wider MYH9-related disease family can also involve hearing, kidney, and eye problems in some people, tell your provider about any changes in your hearing, kidneys, or vision [3].
What is the bottom line on May-Hegglin anomaly?
May-Hegglin anomaly involves abnormal platelets and a low platelet count, but that does not mean you will have problems. Much depends on how low your platelet count is, and many people still have enough platelets to prevent serious blood loss, while others are at risk of severe bleeding [1].
Your next step: if you have a low platelet count with giant platelets, or a family history of the condition, talk with your healthcare provider so you understand which precautions apply to you, and ask whether genetic counseling is right for you and your partner [1].
Frequently Asked Questions
Is May-Hegglin anomaly a type of cancer?
No. It is an inherited genetic disorder of platelets, not a cancer.
Can May-Hegglin anomaly be cured?
May-Hegglin anomaly is a lifelong genetic condition, but most people do not have symptoms serious enough to need treatment, and providers take extra precautions before surgery or procedures.
How common is May-Hegglin anomaly?
May-Hegglin anomaly is rare, with fewer than 200 cases reported in medical studies.
Do people with May-Hegglin anomaly always bleed easily?
No. Many people have enough healthy platelets to prevent bleeding symptoms, and how severe symptoms are depends on how low the platelet count is.
What are Döhle bodies?
Döhle bodies are small rod-shaped structures inside leukocytes, a type of white blood cell, and they are one of the three features that help providers recognize May-Hegglin anomaly.
Can I play sports if I have May-Hegglin anomaly?
You may need to avoid or take precautions with activities where it is easy to get hurt, such as contact sports. Ask your provider what is safe for you.
Does May-Hegglin anomaly affect pregnancy?
Most people go on to deliver healthy babies without complications, but any condition that raises the chance of bleeding poses risks, so you may need additional monitoring from your pregnancy provider.
What gene is responsible for May-Hegglin anomaly?
A mutation in the MYH9 gene. Epstein, Fechtner, and Sebastian syndromes are related MYH9 disorders.
What is a normal platelet count?
A normal platelet count is about 150,000 to 450,000 per microliter of blood; fewer than 150,000 is considered low. In May-Hegglin anomaly, counts range from about 40,000 to 80,000 up to normal values.
Should I see a genetic counselor?
Seeing a genetic counselor may be a good idea if you plan to have biological children. If you or your partner has May-Hegglin anomaly, there is a 50% chance your child will have it too.
Related Reading
Platelet Count (PLT) Blood Test: Normal Range, Low and High Results Explained explains what a platelet count measures and what abnormal results mean.
Bernard-Soulier Syndrome: The Rare Bleeding Disorder That Leaves You With Fewer, Larger Platelets — and Why Most People Still Live Full, Active Lives covers another inherited disorder with large platelets and bleeding.
Immune Thrombocytopenia: Symptoms, Causes, and Treatment explains a common low-platelet condition that inherited disorders can mimic.
Peripheral Blood Smear: Why It's Done, How It Works and What It Shows describes the microscope test that shows platelet size and cell features.
References
Cleveland Clinic. May-Hegglin Anomaly. Cleveland Clinic. September 25, 2024. https://my.clevelandclinic.org/health/diseases/may-hegglin-anomaly
Chen W, Arif AR, Ding Y, et al. A proactive large platelet-driven screening strategy for the early recognition of MYH9-related disease: a Chinese prospective cohort study. Res Pract Thromb Haemost. 2026;10(5):106824. PMID 42598527. https://doi.org/10.1016/j.rpth.2026.106824
Goto S, Sasaki A, Nishio SY, et al. The clinical details of MYH9-related disease and DFNA17 in a large Japanese hearing loss cohort. Genes (Basel). 2026;17(2). PMID 41751538. https://doi.org/10.3390/genes17020154
Medical disclaimer
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. The clinical information in this guide reflects source material last reviewed in September 2024; the “What the research says” section draws on more recent studies.
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