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3 Things to Know About Inhibitors

Without question, factor clotting concentrates help people with hemophilia and other bleeding disorders lead a healthier life. Factor improves blood clotting and can prevent or stop deadly bleeding episodes.

But what happens if the factor stops working?

In some cases, a patient’s immune system can develop a resistance to factor. When this happens, the body stops accepting the factor as a natural part of the blood supply and creates an antibody called an inhibitor.

Antibodies are normally a positive response by the body to help fight off infection. But in the case of hemophilia, the antibody/inhibitor can be detrimental. True to its name, it inhibits treatment for bleeding episodes by destroying the factor.

Although no one knows why inhibitors occur, it is essential that hemophilia patients and their caregivers be aware of this serious complication. The Hemophilia Federation of America states that inhibitors occur in up to 30 percent of hemophilia patients, making them one of the most dangerous and costly consequences of the disease.

In order to stop a bleed caused by an inhibitor, patients may require frequent, large amounts of factor concentrates or special blood products such as bypassing agents. Special therapy such as Immune Tolerance Induction (ITI) may also be needed to re-train the body to accept factor treatment. Moreover, inhibitor bleeding complications significantly increase a patient’s need for hospitalization.

While inhibitors cannot be predicted, patients and caregivers can arm themselves with useful knowledge about this complication. There are three main components to understand about inhibitors:

  1. Warning signs
  2. Risk factors
  3. Testing and treatment options

Warning signs

If a patient is not responding well to treatment, an inhibitor may be present. With less severe inhibitors, symptoms may go undetected – primarily because the inhibitor is not affecting the factor treatment. However, more severe inhibitors can lead to serious reactions in patients and can ultimately bring on a dangerous bleed. Anyone vested in the bleeding disorder community must closely monitor treatment response and be able to recognize bleeding symptoms and irregularities.

Risk factors

Even though any patient can develop an inhibitor, there are potential risk factors that may make someone more susceptible to the complication:

  • Age
  • Race/ethnicity
  • Type of hemophilia gene defect
  • Frequency and amount of treatment
  • Family history of inhibitors
  • Type of factor product used
  • Presence of other immune disorders

Testing and treatment options

Although inhibitors are typically detected in the earlier stages of factor treatment, any patient who is unresponsive to treatment should be tested for the complication. And due to their evolving development, children receiving factor should be tested for inhibitors at least once a year.

To test for inhibitors, blood tests are done to determine how long it takes for the factor concentrate to cause a person’s blood to clot.  If clotting does not occur within a certain period of time following factor infusion, a Bethesda assay test will be performed to confirm the inhibitor diagnosis and identify the type of inhibitor present.

Patients with inhibitors should also seek care at a hemophilia treatment center (HTC). These specialized health care centers are staffed with professionals experienced in treating blood disorders. These centers routinely test for inhibitors, at patients’ annual physicals and prior to any surgery performed on the patient.

Worthwhile research is underway to increase understanding of inhibitors, including the CDC’s “Inhibitor Project.” The goal is to determine which patients are most likely to develop an inhibitor and what factors put them at higher risk.

In the meantime, hemophilia patients and caregivers must build awareness about inhibitors. A collaborative effort between patients, caregivers and healthcare professionals can help prevent potentially dangerous complications.

Mark Helm owns and operates Herndon Pharmacy, a specialty provider of factor products to individuals with hemophilia and other rare bleeding disorders. A lifelong hemophilia patient, Helm has dedicated his life and career to advancing care and treatment options for patients with chronic blood conditions. 

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