A small number of serum lipids were found to be rhythmic in both RA patients and controls, including 9HOTrE, 12(13)EpOME, 13HOTrE and the ceramides CER[N(18)DS(24)], CER[N(18)DS(26)], CER[N(22)DS(18)], CER[N(24)DS(18)] and CER[N(29)S(18)]. The gene discussed is CBLN1; the disease is rheumatoid arthritis.