Common, Variable, Unclassified Immunodeficiency (“Acquired” Hypogammaglobulinemia)
This designation includes the most common form of hypogammaglobulinemia diagnosed in adults. The disorder is heterogeneous in presentation, with variable age of onset (usually after 2 years of age, most frequently between 15 and 35 years of age) and patterns of in-heritance. The clinical signs and symptoms are similar to X-linked agammaglobulinemia.
A panel of experts who met under the auspices of the World Health Organization (WHO) in 1983 recognized several variants of common variable immunodeficiency.
1. Most variants of “acquired hypogammaglobulinemia” have normal or increased numbers of B lymphocytes in peripheral blood, but the B cells remain immature and do not respond adequately to in vivo stimulation.
2. T-cell function appears deficient in most cases, with abnormally low prolifera-tive responses to T-cell mitogens. T-cell receptor stimulation is followed by re-duced release of interleukins and reduced expression of CD40L (CD159). Thus, lack of proper T-cell help seems responsible for the lack of B-lymphocyte re-sponses.
3. In some patients the defect seems to result from excessive suppressor T-lym-phocyte activity.
Sinopulmonary infections, primarily sinusitis, and bacterial pneumonia are the predomi-nant infections. Chronic obstructive pulmonary disease and bronchiectasis are frequent complications. Intestinal giardiasis is common and in some patients can lead to malab-sorption. Opportunistic infections involving P. carinii, mycobacteria, viruses, and other fungi are more frequent in these patients. Clinical features that differentiate common vari-able immunodeficiency from infantile agammaglobulinemia and other forms of hypogam-maglobulinemia are the increased incidence of autoimmune disease and malignancy among these patients. There is a high frequency of autoimmune cytopenias, pernicious anemia, arthritis, inflammatory arthritis, sprue, and polymyositis. Malignancy, particularly of the gastrointestinal lymphoid system, and nodular lymphoid hyperplasia at the intestinal tract are also common clinical manifestations.
Serum immunoglobulin levels are variably depressed. In general the levels of IgG are 2 SD or more below the normal level for age. The aggregate level of the three major im-munoglobulin isotypes is usually below 300 mg/dL. The patients lack isohemagglutinins and fail to produce specific antibodies after immunization or infection. In contrast to what is observed in infantile agammaglobulinemia, these patients have, as noted, normal or in-creased numbers of B lymphocytes in peripheral blood, and those B cells can often be stimulated in vitro to produce immunoglobulins. Lymphoid tissues and tonsils, lymph nodes and spleen may be enlarged. Lymph node biopsies show morphological changes including necrobiosis of the follicles (also seen in the spleen) and/or reticular cell hyper-plasia (which may be the major contributing factor for the development of lym-phadenopathy and splenomegaly and in some patients seem to evolve into lymphoreticu-lar malignancies).
Overall, therapy is similar to that for infantile agammaglobulinemia. Special emphasis should be directed toward preventing pneumonia and progression to bronchiectasis. IVIg should be administered at a dose and frequency to maintain total IgG levels of greater than 600 mg/dL at all times.