Comprehensive Evaluation of IgM Deficiency

Initial Evaluation

A complete blood count with differential should be performed to assess for cytopenias or abnormalities in lymphocyte counts, as recommended by the American Academy of Allergy, Asthma, and Immunology 1
A comprehensive serum immunoglobulin panel (IgG, IgA, IgM, IgE) is necessary to confirm IgM deficiency and evaluate other immunoglobulin levels, according to the American Academy of Allergy, Asthma, and Immunology 1, 2
Serum protein electrophoresis and immunofixation should be conducted to rule out monoclonal gammopathies, as suggested by the International Myeloma Society 3, 4
Serum free light chain analysis is essential to evaluate for potential plasma cell disorders, as recommended by the International Myeloma Society 3, 4
Specific antibody production testing, including measurement of pneumococcal antibody titers before and after vaccination, should be performed to assess functional antibody responses, as advised by the Infectious Diseases Society of America 5
Opsonophagocytic assay may be considered for a more valuable functional assessment of antibody responses, according to the American Academy of Allergy, Asthma, and Immunology 2

Flow cytometric analysis of lymphocyte subsets, including enumeration of B cells, T cells (CD4+ and CD8+), and NK cells, should be performed, as recommended by the American Academy of Allergy, Asthma, and Immunology 1
Evaluation of memory B cell counts is crucial, particularly in patients with low IgM levels and reduced class-switched memory B cells, which may indicate a permanent form of immunodeficiency, as suggested by the American Academy of Allergy, Asthma, and Immunology 1
T-cell functional studies may be necessary if clinically indicated by history of opportunistic infections, as advised by the American Academy of Allergy, Asthma, and Immunology 1

Complement studies (CH50, C3, C4) should be conducted to rule out complement deficiencies, as recommended by the Infectious Diseases Society of America 5

Coombs test and testing for cold agglutinin disease should be performed if hemolysis is suspected, as suggested by the European Society for Medical Oncology 6

Evaluation for characteristic clinical signs and symptoms of serum viscosity should be performed, as recommended by the National Comprehensive Cancer Network 7, 6
Fundoscopy should be conducted to assess for venous engorgement ('sausaging') in retinal veins, as advised by the European Society for Medical Oncology 6

Anti-myelin-associated glycoprotein, anti-ganglioside M1, and anti-sulfatide IgM antibodies should be tested, as suggested by the European Society for Medical Oncology 6

Bone marrow aspiration and biopsy may be necessary if there is suspicion of lymphoproliferative disorders or if other cell lines are affected, as recommended by the International Myeloma Society and the European Society for Medical Oncology 3, 6
CT scans of chest, abdomen, and pelvis should be performed if organomegaly or lymphadenopathy is suspected, particularly in patients with IgM monoclonal proteins, as advised by the National Comprehensive Cancer Network and the European Society for Medical Oncology 7, 6
Hepatitis C serology should be tested, especially in patients with cryoglobulinemia, as recommended by the National Comprehensive Cancer Network 7
Evaluation for amyloidosis should be performed if clinically suspected, as suggested by the European Society for Medical Oncology 6

Transient deficiencies of IgM can occur in infancy and early childhood, but persistent deficiency in adults warrants thorough investigation, as recommended by the American Academy of Allergy, Asthma, and Immunology 1