Notably, four of the five “classical” reference genes (B2M, GAPDH, HMBS, and HPRT1) systematically occupied the last four positions (9th to 12th, respectively) in the final stability ranking generated by RefFinder, as well as in the four individual rankings generated by geNorm, NormFinder, BestKeeper, and the comparative Δ-Ct method, both when analyzing all experimental samples (AL amyloidosis patients and controls) and when focusing on AL patients only (Figure 3, Supplementary Figures S6 and S7). This evidence concerns the gene HPRT1 and AL amyloidosis.