immunology allergic disorders
Hyper IgM Syndrome
Diagnosis of Hyper IgM Syndrome
CD40 ligand expression and genetic testing Diagnosis of hyper-IgM syndrome is suspected based on clinical criteria, including recurrent sinopulmonary infections, chronic diarrhea, and lymphoid hyperplasia. Serum Ig levels are measured; normal or elevated serum IgM levels and low levels or absence of other immunoglobulins support the diagnosis. Flow cytometry testing of CD40 ligand expression on T-cell surfaces should be done. When possible, the diagnosis is confirmed by genetic testing. Prenatal genetic testing can be offered to women considering pregnancy if they have a family history of CD40 ligand deficiency. Genetic testing of other relatives is not routinely done. Other laboratory findings include a reduced number of memory B cells (CD27) and absence of class-switched memory B cells (IgD-CD27). Family members of known patients should be tested if they have a clinical picture consistent with the disease. 