Medd et al.,1 retrospectively studied the occurrence of paraproteinaemia after allo-SCT in a cohort of 91 patients. They detected a paraproteinaemia incidence of 32%, multiple in the majority of cases, with a predominance of an IgG isotype and with equal kappa/lambda restriction. In this report, the most important risk factor for the development of post-transplant paraproteinaemia was CMV reactivation, which was more frequent when alemtuzumab was included in conditioning regimen. The authors also described a poorer OS in patients with paraproteinaemia, with relapse being the commonest cause of death in this group of patients. None of the patients with paraproteinaemia subsequently developed myeloma or a lymphoproliferative disorder and only one patient developed cryoglobulinemia.