They do not simply result from the direct effects of MM cells on bone cells through the release of deleterious “bone factors” (such as Wnt signaling inhibitors), but rather from the complex interactions between MM cells and their microenvironment, activated accessory cells surrounding MM cells, mainly stromal cells, able to release deleterious bone factors such as RankL (activating OC) and activin A (suppressing OB). The gene discussed is BGLAP; the disease is Miyoshi myopathy.