Introduction: Mucopolysacharridosis IVA (MPS IVA), also known as Morquio A syndrome, is a rare, autosomal recessive disorder caused by a deficiency of the lysosomal enzyme N-acetylgalatosamine-6-sulfate-sulfatase (GALNS). Reduced GALNS activity results in impaired catabolism of glycosaminoglycans (GAGs), keratin sulfate (KS) and chondroitin-6-sulfate (C6S). It leads multisystemic complications involving the musculoskeletal, respiratory, cardiovascular, and digestive systems; however there is no central nervous system impairment. There is no definite therapy for MPS IVA, and current management options are palliative. Method: Thirteen patients were diagnosed as MPS IVA via enzyme activity assay at Samsung medical center in Korea. The GALNS genes of all patients were analyzed. Patients’ charts were retrospectively reviewed about clinical manifestations. Result: Ten patients had severe clinical phenotype, and 2 had intermediate phenotype, on the basis of clinical phenotype criteria. One patient had a mild phenotype, and his final adult height was 168.5cm. Radiologic findings indicated skeletal abnormalities in all patients, especially in the hips and extremities. Eight patients had an odontoid hypoplasia, 3 showed atlantoaxial instability, and 4 patients had no abnormalities except platyspondyly in cervical spine. Six patients had kyphoscoliosis in spine and 10 patients had genu valgum. Two pairs of siblings were included, so 11 different GALNS mutations were detected. c.451C＞A accounted for 23.8% (5/21) and detected in both 2 pairs of siblings. Eight patient tested pulmonary function and all were normal. Conclusion: MPS IVA is a severe progressive systemic skeletal disorder that has the potential to cause disease in most bone-related system. An understanding of the manifestations of MPS IVA may allow early diagnosis and therapy in the early stage may improve the quality of life of patients.