Pathogenic DDX41 variants were the most commonly identified, and in UKBB showed a significantly increased risk of MM (OR 5.7 [95% CI 3.9–8.3], p = 6.0 × 10-20) and increased all-cause mortality (HR 1.35 [95% CI 1.1–1.7], p = 0.0063). Here, DDX41 is linked to Miyoshi myopathy.