Testing for Hyper IgM

Accurate diagnosis is key.

It is important to properly diagnose Hyper IgM Syndrome as early on as possible in order to properly manage and treat the patient. Patients with Hyper IgM Syndrome may present with different kinds of symptoms: from recurrent bacterial infections, to Pneumocystis jiroveci pneumonia (PJP/PCP), chronic diarrhea and/or neutropenia.

If your immunologist suspects that you may fall into one of the Hyper IgM Syndrome Families it is important to get testing done at the right lab that has expertise in testing for Primary Immune Deficiencies (PID), and in particular, Hyper IgM Syndrome and CD40 Ligand Deficiency. The following page will describe the testing needed to confirm diagnosis as well as some of the recommended sites in the US that have the expertise to do these testing.

The first line of testing for Hyper IgM Syndrome would be in addition to the common CBC and Metabolic Panel ordered by your physician. The immunologist will send out blood for immunoglobulin levels that will most likely show normal T-cell counts and B-cell counts. IgM levels that are typically normal or elevated while IgG and IgA levels are very low to non-existent. Once these results are in, the next step will be to test for various types of primary immune deficiencies that result in low immunoglobulin.

The Seattle Children’s hospital has a detailed page on testing for X-linked CD40 Ligand Deficiency that covers the two main tests needed for diagnosis: CD40L Gene Sequencing and CD40 Ligand Protein by flow cytometry. In all likelihood your immunologist will first want to run the CD40 Ligand flow cytometry and based on those results move ahead with CD40L Gene Sequencing.

CD40 Ligand flow cytometry: This is both a protein test and a functional test that uses two different monoclonal antibodies to determine whether CD40 ligand protein is expressed on the surface of activated T cells. It also utilizes a CD40-Ig fusion protein to determine if the expressed CD40 ligand protein is able to functionally bind to CD40. Because this test evaluates both CD40L protein and its function, it is able to identify at least 99% of patients with XHIGM.

CD40L Gene Sequencing: The gold standard for confirming a diagnosis of CD40 ligand (CD40L) deficiency in a patient with suggestive symptoms and abnormal CD40 ligand protein flow.

Choosing a Testing Site

There are several sites around the U.S. that offer testing by flow cytometry for initial screening for CD40L deficiency. These tend to be the medical centers that see many patients with PID and their academic medical centers who may also get licensing to offer their tests commercially. We will focus on the list of labs the Foundation has vetted and we know do a good job testing for CD40 Ligand Deficiency:

Feel free to contact us if you have any specific questions regarding diagnosis or want the foundation’s help in connecting with a physician at one of these diagnostic facilities please.