Considering all the investigations performed, the diagnosis of “Multiple myeloma IgG lambda stage III A associated with type I cryoglobulinemia; JAK2 positive Essential Thrombocythemia” was established and it was considered necessary to start the treatment for multiple myeloma, due to the advanced stage of the disease and the presence of cryoglobulinemia, while there were no criteria for starting or continuing the treatment for ET. The gene discussed is JAK2; the disease is plasma cell myeloma.