Bruton tyrosine kinase inhibitor in non-IgM lymphoplasmacytic lymphoma: a case report and literature review.

Non-Waldenström macroglobulinemia (non-WM) lymphoplasmacytic lymphoma (LPL) is a rare subtype with limited clinical evidence and no confirmed treatment guidelines. Bruton tyrosine kinase (BTK) inhibitors represent one of the mainstay therapies in WM, but their role in non-WM LPL remains unclear. We report a case of IgG-type non-WM LPL successfully treated with a second-generation BTK inhibitor, tirabrutinib. The patient demonstrated a rapid decline in M-protein and improvement in anemia, with a durable partial response. This case adds to the limited literature supporting BTK inhibitor use in non-WM LPL and highlights the need for further studies to define optimal treatment strategies.