MPDU1 and congenital disorder of glycosylation: Only four patients received a confirmed diagnosis of CDG: PMM2-CDG (n = 2), MPDU1-CDG (n = 1), and SLC35A2-CDG (n = 1), whereas in 10 patients, an abnormal TIEF test was secondary to other inherited metabolic disorders: galactosemia (n = 4), hereditary fructose intolerance (n = 2), and peroxisomal disease (n = 2).