In this special issue we want to introduce new insights into a complex relationship between monoclonal gammopathy of unknown significance (MGUS) [
1,
2], monoclonal gammopathy of renal significance (MGRS) [
3], immunoglobulin light chain amyloidosis (AL) [
4] and monoclonal gammopathy with clinical significance (MGCS) [
5]. All of them are categorized as M‑protein related diseases. …