Although eosinophils have been found in close proximity to plasma cells within the BM [183] and they are known to secrete the soluble factors APRIL and IL-6 [91,92], which somehow could be involved in MM cell proliferation, it remains unclear whether their activity is relevant to BM plasma cells maintenance [91] or not [93,184]. This evidence concerns the gene TNFSF13 and Miyoshi myopathy.