In MM patients, serum GDF-15 positively correlated with the concentrations of involved (i.e., κ in patients with monoclonal protein including κ-type light chains and λ in patients with λ-type monoclonal protein) free light chains in serum (R = 0.33; p = 0.004; Figure 2(a)) and involved light chains in urine (R = 0.35; p = 0.002) as well as with total (κ plus λ) serum free light chains (R = 0.35; p = 0.002) and urine light chains (R = 0.37; p = 0.001). This evidence concerns the gene GDF15 and Miyoshi myopathy.