Novel BTK Mutation in Patient with Late Diagnosis of X-Linked Agammaglobulinemia.

X-linked agammaglobulinemia (XLA) is a genetic disorder with mutation in Bruton's tyrosine kinase (BTK). Defects in B cell development and immunoglobulin production lead to recurrent infections following loss of maternal IgG at 6 months of age. A 55-year-old male with a longstanding common variable immunodeficiency diagnosis on infusion therapy presented to the clinic with cutaneous T-cell lymphoma, which inspired overall repeat evaluation.