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Monoclonal gammopathy of undetermined significance (MGUS) is a necessary precursor condition to multiple myeloma (MM). Given the role of autophagy in modulating MM risk, we investigated whether genetic variation in autophagy-related genes influences susceptibility to MGUS. We analyzed the association of 34,042 common autophagy-related single nucleotide polymorphisms (SNPs) with MGUS across six independent cohorts, five from Europe and one from North America, comprising 2317 MGUS cases and 282,358 controls. We also assessed their impact on immune parameters, including absolute counts of 91 blood-derived immune cell subsets and 103 circulating immunological proteins. Meta-analysis revealed a genome-wide significant association between the ULK4_rs6599175C allele and increased MGUS risk (p = 3.35 × 10⁻⁸). Carriers of this allele showed reduced counts of memory B cell subsets (IgM+CD38+CD27+ and IgD+IgM+CD27+; p =.0038 and p =.0056, respectively) and natural effector B cells (CD24+CD38+IgD+IgM+ cells; p =.0060). Although these associations were not statistically significant after multiple testing correction, they suggest a role of ULK4 in early B-cell differentiation. Additionally, the CDKN2A_rs2811710 variant showed a suggestive association with MGUS risk (p = 2.17 × 10⁻⁴), affecting transcription factor binding involved in B-cell proliferation and differentiation, although it lacked association with immune markers. In conclusion, we confirm a genome-wide significant association of the ULK4 locus and MGUS risk, supporting its role in early B-cell differentiation, and identify CDKN2A as a candidate susceptibility locus warranting further investigation.