Humans ; Leukemia, Biphenotypic, Acute ; Leukocytosis

Objective:To explore the treatment of the patients with severe phenotype of mucopolysaccharidosis (MPS) type ⅣA by analysing the clinical feature and diagnosis.Methods:Two pediatric patients diagnosed as MPS ⅣA in severe form were enrolled in Children′s Hospital Affiliated to Zhengzhou University from August 2021 to April 2022.Two children from 2 pedigrees with the main manifestations of short stature and bone deformities were retrospectively included.The clinical manifestations, biochemical indexes, and bone imaging findings were retrospectively analyzed.Peripheral blood leukocytes were collected and subjected to the N-acetylgalactosamine-6-sulfatase (GALNS) assay and genetic sequencing.Gene analysis of amniotic fluid cells at the 18 th week of the second pregnancy of the mother of case 2 was performed for prenatal diagnosis.Allogeneic hematopoietic stem cell transplantation (allo-HSCT) was performed in both patients and to explore the treatment of patients with MPS ⅣA. Results:Both cases presented clinical manifestations of short stature, joint laxity, pectus carinatum, and genu valgus.X-ray examination revealed the decreased bone mineral density, ulnar deviation of the radial epiphysis, kyphosis and scoliosis.The respiratory and skeletal systems were affected in both patients, and the optic nerve was suspiciously affected. GALNS gene analysis showed that there were 2 missense mutations of c. 1019G>A (p.G340D) and c. 706C>G (p.H236D) in case 1, and 2 missense mutations of c. 425A>G (p.H142R) and c. 463G>A (p.G155R) were detected in case 2.Mutations in both cases were inherited from their fathers and mothers, which were all newly discovered that have not been reported.Only the c. 463G>A mutation was detected in the amniotic fluid cells of the mother of case 2.It is confirmed that case 2 was the carrier of MPS ⅣA, whose gene mutation was from the mother, and case 2 did not suffer the same disease as the proband.Both cases were treated with allo-HSCT with full donor chimerism and no severe transplant complications were reported.Their GALNS activity was within the normal range, and the scores of activities of daily living were higher than those before transplantation. Conclusions:The MPS ⅣA patients with severe phenotype is a rare autosomal recessive disease caused by GALNS mutations that is difficult to diagnose and poor prognosis.Early detection, diagnosis, and effective treatment contribute to improve the long-term quality of life.The allo-HSCT is an effective therapeutic strategy for MPS ⅣA.