2025 – PAGE 112 – ALLERGY & IMMUNOLOGY

AGAMMAGLOBULINEMIA (AKA X-LINKED AGAMMAGLOBULINEMIA, AKA BRUTON’S AGAMMAGLOBULINEMIA)

Agammaglobulinemia (AKA X-linked agammaglobulinemia or Bruton’s agammaglobulinemia) is X-linked, so it is seen in Boys. There is a total absence of B cells, which means there are NO IMMUNOGLOBULINS. NO Igs! Labs may show high T-cell counts. Patients have tiny or absent tonsils and no palpable lymph nodes. It results in recurrent Bacterial infections and presents around 6 months of age. You might be presented with a child who has a history of “many antibiotic courses.” This could refer to recurrent infections with enCAPSulated organisms, especially Pseudomonas, Streptococcus pneumonia, and Haemophilus influenza. Look for sepsis, meningitis, and recurrent pneumonia. Pneumocystis pneumonia (AKA PCP) does NOT occur in this disorder. If you see PCP, think Hyper-IgM or SCID! TREAT with IVIG for life and give prophylactic antibiotics. BMT is curative.

MNEMONIC: The age of presentation (6 months) happens to be around the same age when the mother’s immunoglobulins/antibodies begin to wane!

PEARL: C1-C4 complement deficiency also results in bacterial infections, but not as severe. CH50 is a good lab test to differentiate these two entities. CH50 is low in C1-C4 complement deficiency and normal is Bruton’s agammaglobulinemia. When CH50 is normal, it means ALL of the complement pathways are okay (C1–C9).

TRANSIENT HYPOGAMMAGLOBULINEMIA OF INFANCY

In transient hypogammaglobulinemia of infancy, B-cells are not deficient, but there are low levels of IgG ± IgA. Infections similar to Bruton’s (encapsulated organisms) start at around 3–6 months of age. Since the child will start developing his/her own immunoglobulins, NO TREATMENT is necessary in asymptomatic infants, but antibiotic prophylaxis may be useful in those who have recurrent sinopulmonary infections. The hypogammaglobulinemia can last for years, but children usually outgrow the problem by about 3–6 years of age. Antibody titers to the protein antigens of organisms the child has been immunized against are normal. Titers against polysaccharide antigens may be low (low-yield fact).