Abstract: Objective　To explore the clinical features, diagnosis, and treatment of congenital disorder of glycosylation type 1a (CDG-Ia), a rare inherited metabolic disease. Methods　The clinical data and the gene detection results of one case of CDG-Ia which was discovered because the case had encephalopathy and hepatopathy were retrospectively analyzed. The related literatures were reviewed. Results　Male infant suffered with face and trunk rash, motor development retardation, malnutrition, cheek fat plump, low limbs muscle tone, and bilateral crater nipple at 3 months old. Abnormal liver function and mild renal impairment were found after examination. The development quotient was low. Head MRI showed that bilateral frontal and temporal sulcus widening, and cerebellar atrophy. Urinary organic acids, amino acids, carnitine, and biotin activities were normal. Gene sequencing revealed that there were two heterozygous mutations, c.430T>C (p.F144L) and c.713G>C (p.R238P), in the PMM2 gene. The diagnosis of CDG-Ia was confirmed. Both of the infant’s parents were healthy, and each of them carries a pathogenic mutation. The infant had an elder brother who had mental disorder and died for liver and kidney function damage and hydronephrosis at 8 months old. Conclusion　CDG-Ia is an autosomal recessive disease. For infants with unexplained multiple organ damage, especially combined with intelligent and motor development retardations, strabismus, nipple retraction, and cerebellar atrophy, the possibility of CDG-Ia should be considered. Gene detection of PMM2 can help the diagnosis.