Can monoclonal IgM kappa light chain gammopathy turn into multiple myeloma?

It can. Yes, it can . It will depend on how much is the quantity of the monoclonal proteine, how many plasma cells on the bone marrow and ultimately whether one has end organ damages/ whether some other organs are affected significantly by the monoclonal protein. That is why some blood work, imaging study and bone marrow biopsy need to be done.