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Key Features

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Essentials of Diagnosis
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  • Recurrent bacterial infections, typically due to encapsulated pyogenic bacteria

  • Low immunoglobulin levels

  • Inability to make specific antibodies to vaccine antigens or infections

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General Considerations
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  • Can be either congenital or acquired

  • Defined as hypogammaglobulinemia with low levels of one or more of the immunoglobulins: IgM, IgG, and IgA

  • As a group, antibody deficiencies represent nearly half of all primary immunodeficiency diseases that can be classified into

    • Defects of B-cell development

    • Defects in Ig class switching

    • Functional B-cell deficiency

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Symptoms and Signs
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  • Defects in B-cell development

    • Patients are generally immunologically normal with the exception of a severe reduction of B cells in the blood and infections that result from their absence

    • Patients with early defects

      • Have little detectable lymphoid tissue

      • May lack tonsils or palpable lymph nodes

    • Patients with later defects may have palpable lymphoid tissue

    • In both groups, size of spleen is generally normal

  • Defects in class switching

    • Presents with various associated features depending on the genetic cause

    • Patients with defects in CD40L and CD40 can have

      • Risk of associated opportunistic infection with Pneumocystis and Cryptosporidium

      • Hypoplastic lymphoid tissue

    • Patients with defective activation-induced cytidine deaminase (AICDA) can have associated autoimmunity, including

      • Idiopathic (or immune) thrombocytopenic purpura (ITP)

      • Hemolytic anemia

      • Autoimmune hepatitis

      • Inflammatory bowel disease

      • Arthritis

      • Interstitial lung disease

    • Both AICDA and uracil DNA N-glycosylase (UNG) deficient patients suffer from lymphoid hyperplasia

  • Transient hypogammaglobulinemia

    • Represents a delay in the onset of immunoglobulin synthesis that results in a prolonged nadir

    • Symptomatic patients have recurrent infections, including upper respiratory tract infections, otitis, and sinusitis

  • Common variable immunodeficiency (CVID)

    • Patients have recurrent infections, most often of the sinopulmonary tract, but chronic gastrointestinal infections may manifest with recurrent diarrhea

    • Patients are at risk for

      • Bronchiectasis

      • Autoimmune diseases (ITP, autoimmune hemolytic anemia, rheumatoid arthritis, and inflammatory bowel disease)

      • Malignancies (especially gastric carcinoma and lymphoma)

    • Isolated IgA deficiency

      • Most patients are asymptomatic

      • However, can be associated with

        • Inflammatory bowel disease

        • Allergic disease

        • Asthma

        • Autoimmune disorders (thyroiditis, arthritis, vitiligo, thrombocytopenia, and diabetes)

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Differential Diagnosis
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  • Secondary causes of decreased amount of immunoglobulin in the peripheral blood

    • Certain medications

    • Protein-losing states

    • Malnutrition

    • Autoimmune conditions

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Diagnosis

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Laboratory Findings
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  • Characteristic feature of antibody deficiency is the absence or severe deficiency of one of the three predominant immunoglobulins found in blood, IgG, IgA, or IgM

    • All three immunoglobulin isotypes are severely reduced in early B-cell development defects; although, IgG deficiency is rarely seen in children younger than 4 months due to the presence of placentally transferred maternal IgG

    • In class switching defects, IgM production can be normal or elevated, whereas production of IgG and IgA is deficient

    • In functional B-cell deficiencies, a combination of antibody production abnormalities may be detected

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Treatment

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  • Primary goal is replacing deficient IgG to prevent ...

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