By observing the distribution of iNKT cells in different MM patients, we found that the quantity of iNKT cells which primarily was CD4−CD8+ and DN iNKT cells were defective in NDMM and RMM patients, the production of Th1 cytokines (IFN‐γ and TNF) by iNKT cells also reduced and Th2 cytokines (IL‐4 and IL‐13) by iNKT cells increased in NDMM and RMM patients. The gene discussed is IFNG; the disease is Miyoshi myopathy.