X-linked Agammaglobulinemia (XLA)
X-linked agammaglobulinemia (XLA) is an X-linked syndrome that typically presents in childhood with recurrent sinopulmonary infections (otitis, sinusitis, pneumonia, etc.), low immunoglobulin levels and low or absent B cells. Patients may also have recurrent gastrointestinal infections (Giardia, Campylobacter, rotavirus, etc.), enteroviral meningoencephalitis, arthritis and inflammatory bowel disease.
Key Clinical Features
- Recurrent sinopulmonary infections: Pneumonia, bronchitis, sinusitis, otitis media, etc.
- Hypogammaglobulinemia: Markedly low IgG, IgM and IgA levels that become apparent after maternal antibody has diminished
- Diminished lymphatic tissue: Small or absent tonsils, adenoids and lymph nodes
- B lymphopenia: Low or absent B cell numbers
Molecular Defects Associated with XLA
- Btk (Bruton's tyrosine kinase)
Suggested Testing Approach
- Flow cytometry only or flow cytometry + gene sequencing: 7 cc whole blood in heparin sodium anticoagulant (green top tube) shipped overnight at ambient temperature. Please include 5-7 cc of whole blood from a normal individual in a separate tube as a control for flow cytometry studies in any shipped samples.
- Gene sequencing only: 2-5 cc whole blood in heparin sodium or EDTA anticoagulant. Ship overnight at ambient temperature.
- Alternative sources of DNA can be used as well (buccal swabs, CVS, etc.). Please contact the lab for questions or information.
- Flow cytometry: Platelets are evaluated by flow cytometry for intracellular Btk protein expression
- Gene sequencing: All exons (-1 to 18) are evaluated by bidirectional sequencing from genomic DNA. Sequencing includes all exon/intron boundaries.
CPT Codes for Testing
- Flow cytometry: 83907(1), 88184(1), 83912(1)
- Btk gene sequencing: 83907(1), 83981(1), 83898(19), 83894(19), 83904(38), 83912(1)
- Flow cytometry: Five business days from receipt of sample.
- Gene sequencing: Btk — Four to six weeks from receipt of sample.
Testing Packet for X-linked Agammaglobulinemia
Sample Submission Form, Available Tests and Sample Requirements/Shipping Instructions (PDF)