Hi thanks for asking question. You have plasma cell disorder that is MGUS. Regular follow up done for it as it might get converted into smoldering and then multiple myelona that is plasma cell tumour. As far as prominent liver concerned there are variety of causes. You have mentioned about some immune issue.So autoimmune disease or connective tissue disease like rheumatoid arthritis or sjogren syndrome like disease might enlarge liver. Second if you have associated abdomen pain, vomiting , yellow sclera do your serum viral marker to rule out viral hepatitis. If bleeding from any area present do your serum ldh and blood reticulocyte testing to rule out hemolytic anemia.Blood peripheral smear examination also helpful. Meanwhile take nutritional diet with less fat and fried food. Regularly consult doctor and even if condition worsening liver biopsy done to rule out metastasis of any primary tumour. Wish you good health