Is There a Clinical Significance of Very Low Serum Immunoglobulin E Level?

Purpose: It has been well known that high serum immunoglobulin (Ig) E levels are associated with allergies, parasitic infections and some immune deficiencies; however, the potential effects and clinical implications of low IgE level on the human immune system are not well known. To determine the disorders accompanying very low IgE levels in children and adults. Methods: The patients whose IgE levels were determined between January 2015 and September 2020 were analyzed, and the ones with an IgE level <2.5 IU/mL were included in the study. Demographic data, immunoglobulin levels, auto-antibody results, and the diagnoses of the patients were noted from the electronic recording system of the hospital. Result: The IgE levels were measured in 34,809 patients (21,875 children, 12,934 adults), and 180 patients had IgE levels <2.5 IU/mL. Eighty patients were children (0.37%), 100 were adults (0.77%). There was a malignant disease in 45 (11 of them children) (25%), autoimmune diseases in 30 (4 of them children) (16.7%) and immunodeficiency in 19 (16 of them children) (10.6%) of the patients. The most common reasons were other disases, immunodeficiency and malignancy in children; and malignancy, autoimmune disorders and other diseases in the adults, in rank order. The IgE level did not show any correlation with the levels of other immunoglobulins.Conclusion: Although rare, a low IgE level has been shown to accompany malignancies, autoimmune disorders and immune deficiencies. Patients with very low IgE levels should be carefully monitored for systemic disorders.