FKBP11 and Miyoshi myopathy: 41 (215949_x_at) IGHM encodes for the constant part of the heavy mu chain and is a marker of B-cell differentiation, as has also been shown by others.42 In a similar fashion, (219117_s_at) FKBP11, a member of the FKBP family of peptidyl-prolyl cis/trans isomerases, has been found to be uniquely highly expressed in MM;43 its downregulation in the low CIg group furthers supports the dedifferentiation of the low immunoglobulin-producing plasma cells.