ABSTRACT
Abstract Mucopolysaccharidosis type IH (MPS IH) is caused by homozygous IDUA gene pathogenic variants. This results in deficiency of the enzyme α-L-iduronidase (IDUA), which is necessary for the degradation of glycosaminoglycans (GAGs). This study outlines the long-term outcomes in adult Irish patients affected with MPS IH, who were followed up for mean 28 years post Haematopoietic Stem Cell Transplantation. Nineteen adult MPS IH patients underwent HSCT in childhood. The participant cohort represents 6 families. Among the 13 patients with Irish Traveller ethnicity, 6 patients were either siblings or first cousins. All these related patients were homozygous for p. Trp402Ter (W402X). Mean age at the first transplantation was 8 months (range 3-21). Five patients had undergone a second transplantation (n=5, 26%) in childhood, due to graft failure. None of the patients had a cardiac valve surgery at the time of the study. 14/19 patients had mild to moderate aortic or mitral valve insufficiency or stenosis. 3/19 patients used non-invasive ventilation at night. Two patients had tracheostomy in situ. Both sensorineural as well as conductive hearing defects. No corneal clouding post corneal transplantation (n=8) was observed. Six patients attended regular secondary school. Multidisciplinary follow-up is needed to address the disease specific complications in adulthood.