As expected, AQP9, CD27, and HVCN1 had a mild to moderate diagnostic value in CD, especially when using normal intestinal tissues as controls, and the diagnostic value of AQP9 was much better than that of CD27 and HVCN1. Although the diagnostic value of CD27 has been reported in multiple myeloma (31), its diagnostic value in CD has not been described previously. The gene discussed is AQP9; the disease is plasma cell myeloma.