May-Hegglin Anomaly

What is May-Hegglin anomaly?

May-Hegglin anomaly is a rare genetic disorder where your body makes abnormally large platelets and too few platelets (thrombocytopenia). Platelets are blood components that help form clots to stop the bleeding when you’re injured.

Having May-Hegglin anomaly means you were born with a genetic mutation (change) that may cause you to bleed or bruise more easily than someone without the disorder. You may be more likely to experience blood loss (hemorrhage) after a major surgery. On the other hand, many people with May-Hegglin anomaly don’t experience symptoms or major issues at all.

Regardless of whether you’re experiencing symptoms, it’s important to know if you have May-Hegglin anomaly. That way, you and your providers can take steps to reduce your risk of injury or blood loss.

What is the triad of May-Hegglin anomaly?

May-Hegglin anomaly causes three distinct features, including:

• Abnormally large platelets (macrothrombocytopenia).
• Low platelet count (thrombocytopenia).
• Small rod-shaped structures inside your leukocytes (a type of white blood cell) called Döhle bodies.

These three criteria help providers distinguish May-Hegglin anomaly from other disorders that cause abnormal platelets.

How common is this condition?

May-Hegglin anomaly is a rare condition, with fewer than 200 cases reported in medical studies. As it’s so rare, healthcare providers don’t often suspect it at first. Your provider will likely need to rule out several other conditions that may affect your platelets before you receive a diagnosis.

What are the symptoms of May-Hegglin anomaly?

Many people with May-Hegglin anomaly have enough healthy platelets to prevent symptoms related to excessive bleeding. If you do have symptoms, they’ll likely depend on how low your platelet count is.

Signs and symptoms may include:

• 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.

What causes May-Hegglin anomaly?

With May-Hegglin anomaly, you inherit a mutation (change) on your MYH9 gene from one of your biological parents. The mutation causes problems with how platelets form so they’re too large and unusually shaped. The MYH9 mutation also causes a low platelet count that may cause you to bruise or bleed easily.

People inherit May-Hegglin anomaly in an autosomal dominant pattern. This means you only have to have one copy of the mutated MYH9 gene to have the disorder.

How is May-Hegglin anomaly diagnosed?

Most people don’t realize they have May-Hegglin anomaly until a blood test done for an unrelated reason shows a low platelet count and giant platelets. For example, you may learn there’s an issue during routine blood work to screen for health issues during pregnancy.

Tests to diagnose May-Hegglin anomaly include:

• Complete blood count (CBC): This test can show if your platelets are low. Platelet counts in this condition vary from 40,000 to 80,000 platelets per microliter of blood to normal platelet values. For reference, fewer than 150,000 platelets per microliter are considered low.
• Peripheral blood smear (PBS): This test can show if you have large platelets. Providers also look for Döhle bodies (the rod-shaped structures) in your leukocytes.
• Genetic tests: This test can show if you have a mutation involving your MYH9 gene.

Your healthcare provider may recognize other signs of low platelets like an increased bleeding time.

How is May-Hegglin anomaly treated?

Most people with May-Hegglin anomaly don’t experience symptoms that are serious enough to need treatment. Still, your healthcare provider may need to take extra precautions to prevent serious blood loss after surgery. For example, your provider may give you desmopressin by IV or a platelet transfusion before a medical procedure to offset any risk of severe blood loss.

You may also need a platelet transfusion to restore your levels in case of emergency blood loss.

You may require additional monitoring if you’re pregnant. Although most people with May-Hegglin anomaly go on to deliver healthy babies without complications, any condition that increases your chances of bleeding poses risks. Your pregnancy provider will advise you on what steps to take to protect you and the fetus.

Can May-Hegglin anomaly be prevented?

There’s nothing you can do to keep from getting May-Hegglin anomaly. Still, it may be a good idea to speak to a genetic counselor if you plan to have biological children. If you or your partner has May-Hegglin anomaly, there’s a 50% chance that your child will be born with the disorder, too.

A genetic counselor can help you assess any potential risks and advise you on your options.

What can I expect if I have May-Hegglin anomaly?

May-Hegglin anomaly is a lifelong condition. Fortunately, for most people, this doesn’t mean it interferes with their lives. Many people with this disorder don’t experience symptoms or only have mild symptoms. If it causes a low platelet count, your healthcare provider can recommend ways to manage blood loss if you’re injured.

How do I take care of myself?

One of the best things you can do if you learn you have May-Hegglin anomaly is to speak with your healthcare provider about how to manage the condition. Be informed about:

• Medications: Know which medications may interfere with your platelets, so you can avoid them or take them in safe doses.
• Proper dental care: Taking care of your oral hygiene can prevent bleeding gums.
• Activities that can lead to injury: You may need to avoid or take precautions when you’re doing things where it’s easy to get hurt, like playing contact sports.
• Pregnancy risks: Work closely with your pregnancy provider to monitor your health so May-Hegglin anomaly doesn’t get in the way of you having a healthy pregnancy.

What questions should I ask my healthcare provider?

If you learn you have May-Hegglin anomaly, questions to ask your provider might include:

• How severe is the thrombocytopenia (low platelets)?
• When should I be concerned about low platelet counts?
• Which symptoms should I look out for?
• Which changes can I make in my everyday life to help manage my condition?
• Should my partner and I get genetic counseling?

What is a MYH9-related disorder?

May-Hegglin anomaly is a MYH9-related disorder. These disorders involve a mutation on the MYH9 gene. Research shows that May-Hegglin anomaly and three other conditions involving abnormal platelets and low platelet counts all involve MYH9 mutations. The other three are:

• Epstein syndrome.
• Fechtner syndrome.
• Sebastian syndrome.

As they’re so closely related and share the same cause, it’s likely that eventually, these condition names will fade away, and they’ll all just be “MYH9-related disorder.”