Mannose‐phosphate‐dolichol utilization defect 1 (MPDU1) is involved in the flipping of DPM and dolichol‐phosphate‐glucose (DPG) across the ER membrane and for efficient use of DPM and DPG within the ER lumen.6, 7 MPDU1‐CDG patients have CDG‐I with epilepsy, psychomotor retardation, and skin abnormalities.7, 8, 9 Here, we describe two siblings with a G73E substitution in MPDU1 without skin involvement, but with dilatation of the biliary ducts and dystroglycanopathy symptoms including elevated creatine kinase (CK), dilated cardiomyopathy (DCM), buphthalmos, and glaucoma. This evidence concerns the gene MPDU1 and dilated cardiomyopathy.