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Background: Although secondary hypogammaglobulinemia is more frequent than primary hypogammaglobulinemia, its etiology and management are poorly described, particularly for mild hypogammaglobulinemia., Methods: This retrospective observational study included all adult patients with a gammaglobulin level <6.4g/L on serum electrophoresis identified at Dijon teaching hospital between April and September 2012. Clinico-biological features, etiologies and infectious complications were collected at inclusion and compared between group 1 (gammaglobulin <5g/L, severe hypogammaglobulinemia), and group 2 (gammaglobulin <6.4 and ≥5g/L, mild hypogammaglobulinemia)., Results: Among the 4011 serum electrophoreses, 570 samples from 389 patients had gammaglobulin levels below 6.4g/L: 156 (40%) in group 1 and 233 (60%) in group 2. Mean age±SD was 67 (15) years, and sex ratio was 1.04 (M/F) with no difference between the two groups. An etiology was identified in 79% and 58% of patients in groups 1 and 2, respectively (p<0.0001). The main etiologies were similar in both groups and included malignant hemopathy treated with cytostatic agents (n=129, 33%), smoldering or newly-diagnosed hemopathy without treatment (n=49, 13%) and immunosuppressive treatment (n=91, 23%). The incidence of hypogammaglobulinemia-related infections was 22/100/year, with no significant difference between the two groups (p=0.17). Vaccination coverage against pneumococcus was 33%, and higher in group 1 (46% vs. 24%; p<0.0001). When no cause was known at inclusion, an etiology was discovered in 22/130 patients (17%), 11 in each group., Conclusions: Though mild hypogammaglobulinemia does not meet the classical criteria for hypogammaglobulinemia (<5g/L), the etiology and infectious risk are similar. It therefore requires investigation and vaccination., (Copyright © 2014 European Federation of Internal Medicine. Published by Elsevier B.V. All rights reserved.)

The discovery of hypogammaglobulinemia, which is defined as a plasmatic level of immunoglobulin (Ig) under 5 g/L is rare in clinical practice. However, the management of immunodepressed patients in rheumatology, sometimes due to the use of immunosuppressive treatments such as anti-CD20 in chronic inflammatory rheumatisms, increases the risk of being confronted to this situation. The discovery of hypogammaglobulinemia in clinical practice, sometimes by chance, must never be neglected and requires a rigorous diagnosis approach. First of all, in adults, secondary causes, in particular lymphoid hemopathies or drug-related causes (immunosuppressors, antiepileptics) must be eliminated. A renal (nephrotic syndrome) or digestive (protein-losing enteropathy) leakage of Ig is also possible. More rarely, it is due to an authentic primary immunodeficiency (PID) discovered in adulthood: common variable immunodeficiency (CVID) which is the most frequent form of PID, affects young adults between 20 and 30 years and can sometimes trigger joint symptoms similar to those in rheumatoid arthritis; or Good syndrome, which associates hypogammaglobulinemia, thymoma and recurrent infections around the age of 40 years. In most cases, after confirming hypogammaglobulinemia on a second test, biological examinations and thoracic-abdominal-pelvic CT scan will guide the diagnosis, after which the opinion of a specialist can be sought depending on the findings of the above examinations. At the end of this review, we provide a decision tree to guide the clinician confronted to an adult-onset hypogammaglobulinemia., (Copyright © 2010 Société française de rhumatologie. Published by Elsevier SAS. All rights reserved.)