The mononuclear cells from AL amyloidosis patients had lower expression levels than the cells from myeloma patients for BDNF, calmodulin, phospho‐TBK1, and phospho‐ULK1 in CD4+ T cells and phospho‐GSK3β in monocytes, but higher levels of HO1 in monocytes. Here, BDNF is linked to plasma cell myeloma.