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X-Linked Agammaglobulinemia (XLA) Diagnosis: Symptoms & Testing

XLA (Bruton's agammaglobulinemia) is a primary immunodeficiency caused by BTK gene mutations → absent B cells → profoundly low immunoglobulins. Presents in males <2 years after maternal IgG wanes.

Clinical Features

Recurrent sinopulmonary infections (otitis, sinusitis, pneumonia) – encapsulated bacteria (S. pneumoniae, H. influenzae).
Chronic enteroviral infections (meningoencephalitis, dermatomyositis-like syndrome).
Failure to thrive, chronic diarrhea (Giardia, Campylobacter).
Absent tonsils/lymph nodes; no lymphoid tissue on exam.
Autoimmune phenomena (arthritis, cytopenias) paradoxically occur.

Diagnostic Workup

Additional Studies

Chest X-ray/CT: Bronchiectasis, chronic lung changes.
Sinus CT: Chronic sinusitis.
MRI brain: If neurologic symptoms (enterovirus).
Sweat chloride: Rule out CF (can mimic recurrent infections).

Management

IVIG/SCIG replacement lifelong.
Prophylactic antibiotics (controversial; individualized).
Live vaccines contraindicated.
Genetic counseling for family.

Early diagnosis prevents irreversible organ damage; newborn screening for SCID detects some XLA.

Blood Disorders - Related Articles

Test	Expected in XLA
Immunoglobulins (IgG, IgA, IgM)	Very low/absent (IgG <200 mg/dL typical)
B cells (CD19+)	<1% of lymphocytes (absent)
T cells (CD3+, CD4+, CD8+)	Normal or elevated
Vaccine titers	Absent specific antibodies
BTK genetic testing	Pathogenic variant confirms diagnosis
Bone marrow	Arrest at pre-B stage; no mature B cells