Germline DDX41 mutations are involved in familial myelodysplastic syndromes (MDS) and acute myeloid leukemias (AML). We analyzed the prevalence and characteristics of DDX41-related myeloid malignancies in an unselected cohort of 1385 patients with MDS or AML. Using targeted next-generation sequencing, we identified 28 different germline DDX41 variants in 43 unrelated patients which we classified as causal (n=21) or unknown significance (n=7) variants. We focused on the 33 patients having causal variants, representing 2.4% of our cohort. Median age was 69 years, most patients were males (79%). Only 9 patients (27%) had a family history of hematological malignancy, while 15 (46%) had personal history of cytopenias years prior to MDS/AML diagnosis. Most patients had normal karyotype (85%) and the most frequent somatic alteration was a second DDX41 mutation (79%). High-risk DDX41 MDS/AML patients treated with intensive chemotherapy (n=9) or azacitidine (n=11) had an overall response rate of 100% and 73%, respectively, with a median overall survival of 5.2 years. Our study highlights that germline DDX41 mutations are relatively common in adult MDS/AML, often without known family history, arguing for systematic screening. Salient features of DDX41-related myeloid malignancies include male preponderance, frequent pre-existing cytopenias, additional somatic DDX41 mutation and relatively good outcome.