Thus, development of highly specific mouse mAbs against human CRBN may provide a tool to determine: (1) the levels of CRBN; (2) the localization of CRBN; (3) the functional roles of CRBN in each individual cellular organelle; and (4) especially to confirm the relationship between CRBN expression and IMiD sensitivity or between CRBN expression and proteasome inhibitor sensitivity in patients with MM. The gene discussed is CRBN; the disease is Miyoshi myopathy.