Four novel mutations in the N-acetylgalactosamine-6-sulfate sulfatase gene among Egyptian patients with Morquio A disease

Oral immunotherapy tolerizes mice to enzyme replacement therapy for Morquio A syndrome

Immune response to therapeutic enzymes poses a detriment to patient safety and treatment outcome. Enzyme replacement therapy (ERT) is a standard therapeutic option for some types of mucopolysaccharidoses, including Morquio A syndrome caused by N-acetylgalactosamine-6-sulfate sulfatase (GALNS) deficiency. Current protocols tolerize patients using cytotoxic immunosuppressives, which can cause adverse effects. Here we show development of tolerance in Morquio A mice via oral delivery of peptide or GALNS for 10 days prior to ERT. Our results show that using an immunodominant peptide (I10) or the complete GALNS enzyme to orally induce tolerance to GALNS prior to ERT resulted in several improvements to ERT in mice: (a) decreased splenocyte proliferation after in vitro GALNS stimulation, (b) modulation of the cytokine secretion profile, (c) decrease in GALNS-specific IgG or IgE in plasma, (d) decreased GAG storage in liver, and (e) fewer circulating immune complexes in plasma. This model could be extrapolated to other lysosomal storage disorders in which immune response hinders ERT.

Mutation spectrum and pivotal features for differential diagnosis of Mucopolysaccharidosis IVA patients with severe and attenuated phenotype

Mucopolysaccharidosis IVA (MPS IVA) is a lysosomal storage disease caused by biallelic mutations in GALNS gene and characterized by progressive skeletal deformities with short stature. The aim of this study was to evaluate the genotype, longitudinal height measurement and clinical features of MPS IVA patients. Thirty-two patients from 22 families were enrolled. The ages of patients at diagnosis ranged from two months to 18 years of age, and followed up for three to twenty years. They were classified as severe and attenuated form (intermediate and mild) according to their height measurements. The mean height standard deviation scores (SDS) for Turkish standards at 0-3, 5 and 10 years of ages were found to be -1.1, -4.2 and -7.3 respectively in patients with severe phenotype, while they were +0.4, -1.5 and -3 for intermediate phenotype. Patients with severe form reached a mean final height of -8.5 SDS, and mild phenotype -3.6 SDS. The most common initial and current symptoms in the patients with the severe phenotype were pectus carinatus and/or kyphosis deformities which occurred between 5 months and 3 years of age, and genu valgum deformity which developed after 3 years of age. However, kyphoscoliosis was the most common initial and current findings in the attenuated phenotype. Although, initial symptoms appeared in early childhood in the intermediate phenotype, similar to the severe phenotype, the clinical findings progressed slowly and genu valgum deformity did not develop. In patients with mild phenotype, the onset of symptoms was after 5 years of age. In conclusion, this study provides significant insights into the initial and follow-up clinical features and height values that contribute to the differential diagnosis of the severe and intermediate phenotypes in early childhood. Eleven mutations in GALNS gene in which one of them is novel (c.416G>A) were associated with the severe phenotype and three mutations (c.1038C>A, c.850T>G, c.752G>A) lead to the attenuated phenotype.