I was recently diagnosed with a rare blood cancer called Waldenstrom's Macroglobulinemia (aka: Lymphoplasmacytic Lymphoma). I've had high IgM, high kappa light chains, and a high kappa/lambda ratio since 2017, it turned into cancer in the past year or so. High kappa light chains alone are not cause for worry, it's only when it is combined with a high ratio and numerous other abnormal bone marrow findings that it becomes cause for concern. Trust your doctor on this one. There is no telling how many people with no issues whatsoever are walking around with high light chains never having a single symptom.