<unk>  <unk>  is a primary immunodeficiency disorder.<unk>  is the most<unk>  antibody deficiency affecting both children and adults. The characteristic immunological defect in<unk>  is impaired B cell differentiation with defective production of immunoglobulin. Impaired B cell differentiation leads to low serum concentrations of immunoglobulin G (IgG), low immunoglobulin A (IgA) and/or immunoglobulin M (IgM), as well poor or absent response to immunization. The majority of patients are diagnosed between the ages of 20 and 40 years. Recurrent bacterial infections of the sino-pulmonary tract (sinusitis and pneumonia) are most<unk>  manifestations of patients with<unk> . Opportunistic and unusual infections are uncommon, but may occur. In addition to recurrent infections, patients with<unk>  have evidence of immune dysregulation leading to autoimmunity. Patients may suffer from chronic lung disease, gastrointestinal and liver disorders, granulomatous infiltrations, lymphoid hyperplasia, splenomegaly, or malignancy. Various forms of primary and secondary hypogammaglobulinemia must be excluded before the diagnosis of<unk> . The diagnosis of<unk>  requires a suggestive clinical history, a reduced total serum concentration of IgG, plus low IgA or IgM, and poor responses to both protein- and polysaccharide-based vaccines.
Common variable immunodeficiency
Combined immunodeficiency
Severe combined immunodeficiency
X-linked severe combined immunodeficiency
X-linked agammaglobulinemia
Wiskott-Aldrich syndrome
Primary immunodeficiency
Chédiak-Higashi syndrome