Additionally, soluble (s)CD138, which is proteolytically shed by matrix metalloproteases and sheddases, is present at high levels in the serum of MM patients and is heavily implicated in disease progression: it acts as a key mediator between MM cells and the BM microenvironment on which they rely, promoting signaling pathways that lead to tumor cell proliferation, angiogenesis, and metastasis. Here, SDC1 is linked to Miyoshi myopathy.