Diagnostic approach of hypogammaglobulinemia in infancy.

Primary B-cell immunodeficiency is the most frequent immune defect in infancy. Selective absence of serum and secretory immunoglobulin IgA is the most common, with rates ranging from 1/333 persons to 1/16 000, among different races. By contrast, it has been estimated that hypo/agammaglobulinemia occurs with a frequency of 1/50 000 persons. Patients with antibody deficiency are usually recognized because they have recurrent infections with encapsulated bacteria or a history of failure to respond adequately to antibiotic treatment. However, some individuals, mainly those affected by IgA deficiency (SIgAD) or transient hypogammaglobulinemia of infancy , may have few or no infections.