[Non-secretory myeloma of heavy mu-chain type]

We report on a patient with a bone marrow plasmacell infiltration, since this case displays some outstanding clinical and laboratory features: the presence of massive splenomegaly and the absence of bone lesions; the cytoplasmic heavy chain type mu, without any light chain detectable by immunofluorescence (IF); the non secretory feature of this plasma cell proliferation. The position of such an entity within the spectrum of B-lymphoproliferative disorders, from mu heavy chain disease to non secretory IgM myeloma, is discussed.