In this report, we document a case of LPL distinguished by the presence of monoclonal IgG-λ immunoglobulin and free λ light chains, alongside its distinctive molecular characteristics and therapeutic outcomes.<h4>Patient concerns</h4>A 58-year-old male presented with fatigue, leukocytosis (75.45 × 109/L, 88.8% lymphocytes), lymphadenopathy, and splenomegaly. The gene discussed is LPL; the disease is Lymphadenopathy.