COG3 and Failure to thrive: Cells: deficient in sialylation of both N‐ and O‐glycans, slower brefeldin A induced disruption of the Golgi matrix, reduction in COG1, COG5, COG6, and COG7 protein levels but not COG2, COG3 and COG4, COG5, COG6, and COG7 were also mislocalizedPatients: cerebellar atrophy, Elevated blood creatine phosphokinase, Alternating esotropia, psychomotor retardation, failure to thrive, intolerance to wheat and dairy products, lack of bowel or bladder control, dry skin with keratosis pilaris, mild contractures of the lower extremities