Our previous work has definitively shown that the peripheral blood of MM patients is colonized by CD19+ clonotypic B cells (Szczepek, Seeberger, Wizniak, Mant, Belch, and Pilarski, 1998), as well as by clonotypic IgM+ B cells (Reiman et al. 2001; Taylor et al. 2002). The gene discussed is CD19; the disease is Miyoshi myopathy.