Psychosocial outcomes of bone marrow transplant for individuals affected by Mucopolysaccharidosis I Hurler Disease: patient social competency

Therapy development for the mucopolysaccharidoses: Updated consensus recommendations for neuropsychological endpoints

Neurological dysfunction represents a significant clinical component of many of the mucopolysaccharidoses (also known as MPS disorders). The accurate and consistent assessment of neuropsychological function is essential to gain a greater understanding of the precise natural history of these conditions and to design effective clinical trials to evaluate the impact of therapies on the brain. In 2017, an International MPS Consensus Panel published recommendations for best practice in the design and conduct of clinical studies investigating the effects of therapies on cognitive function and adaptive behavior in patients with neuronopathic mucopolysaccharidoses. Based on an International MPS Consensus Conference held in February 2020, this article provides updated consensus recommendations and expands the objectives to include approaches for assessing behavioral and social-emotional state, caregiver burden and quality of life in patients with all mucopolysaccharidoses.

Mucopolysaccharidosis Type I: A Review of the Natural History and Molecular Pathology

Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive inherited disease, caused by deficiency of the enzyme α-L-iduronidase, resulting in accumulation of the glycosaminoglycans (GAGs) dermatan and heparan sulfate in organs and tissues. If untreated, patients with the severe phenotype die within the first decade of life. Early diagnosis is crucial to prevent the development of fatal disease manifestations, prominently cardiac and respiratory disease, as well as cognitive impairment. However, the initial symptoms are nonspecific and impede early diagnosis. This review discusses common phenotypic manifestations in the order in which they develop. Similarities and differences in the three animal models for MPS I are highlighted. Earliest symptoms, which present during the first 6 months of life, include hernias, coarse facial features, recurrent rhinitis and/or upper airway obstructions in the absence of infection, and thoracolumbar kyphosis. During the next 6 months, loss of hearing, corneal clouding, and further musculoskeletal dysplasias develop. Finally, late manifestations including lower airway obstructions and cognitive decline emerge. Cardiac symptoms are common in MPS I and can develop in infancy. The underlying pathogenesis is in the intra- and extracellular accumulation of partially degraded GAGs and infiltration of cells with enlarged lysosomes causing tissue expansion and bone deformities. These interfere with the proper arrangement of collagen fibrils, disrupt nerve fibers, and cause devastating secondary pathophysiological cascades including inflammation, oxidative stress, and other disruptions to intracellular and extracellular homeostasis. A greater understanding of the natural history of MPS I will allow early diagnosis and timely management of the disease facilitating better treatment outcomes.

Assessments of neurocognitive and behavioral function in the mucopolysaccharidoses

The mucopolysaccharidoses (MPS) are a group of rare, inherited lysosomal storage disorders in which accumulation of glycosaminoglycans (GAGs) leads to progressive tissue and organ dysfunction. In addition to a variety of somatic signs and symptoms, patients with rapidly progressing MPS I (Hurler), II, III, and VII can present with significant neurological manifestations, including impaired cognitive abilities, difficulties in language and speech, behavioral abnormalities, sleep problems, and/or seizures. Neurological symptoms have a substantial impact on the quality of life of MPS patients and their families. Due to the progressive nature of cognitive impairment in these MPS patients, neurocognitive function is a sensitive indicator of disease progression, and a relevant outcome when testing efficacy of therapies for these disorders. In order to effectively manage and develop therapies that address neurological manifestations of MPS, it is important to use appropriate neurocognitive assessment tools that are sensitive to changes in neurocognitive function in MPS patients. This review discusses expert opinions on key issues and considerations for effective neurocognitive testing in MPS patients. In addition, it describes the neurocognitive assessment tools that have been used in clinical practice for these patients. The content of this review is based on existing literature and information from a meeting of international experts with extensive experience in managing and treating MPS disorders.

Social Functioning and Behaviour in Mucopolysaccharidosis IH [Hurlers Syndrome]

BACKGROUND

Mucopolysaccharidosis type IH (MPS-IH) [Hurlers Syndrome] is a developmental genetic disorder characterised by severe physical symptoms and cognitive decline. This study aimed to investigate the behavioural phenotype of MPS-IH treated by haematopoietic cell transplantation, focusing on social functioning and sleep. Parental stress was also measured.

METHODS

Participants were 22 children with MPS-IH (mean age 9 years 1 month), of whom 10 were male (45%). Parents completed the Social Responsiveness Scale (SRS), Child Behaviour Checklist (CBCL), Children's Sleep Habit Questionnaire and Parent Stress Index, Short Form (PSI-SF).

RESULTS

Twenty-three per cent of children with MPS-IH scored in the severe range of the SRS, suggesting significant difficulties in social functioning. Children with MPS-IH were more than 30 times more likely to receive scores in the severe range than typically developing children. Thirty-six per cent scored in the mild-to-moderate range, suggesting milder, but marked, difficulties in social interaction. Although children with MPS-IH did not show significantly higher rates of internalising, externalising or total behaviour problems than the normative sample, they received scores that were significantly higher on social, thought and attention problems and rule-breaking behaviour, and all the competence areas of the CBCL. Parents of children with MPS-IH did not score significantly higher on parental stress than parents in a normative sample.

CONCLUSIONS

Parents of children with MPS-IH rate their children as having problems with social functioning and various areas of competence more frequently than previously thought, with implications for clinical support.

Outcomes of Long-Term Treatment with Laronidase in Patients with Mucopolysaccharidosis Type I

OBJECTIVE

To evaluate long-term outcomes of laronidase enzyme replacement therapy in patients with attenuated mucopolysaccharidosis type I.

STUDY DESIGN

Retrospective analyses of case notes, laboratory results, and data from clinical trials were used to evaluate urinary glycosaminoglycans, forced vital capacity (FVC), 6-minute walk test (6MWT), height-for-age Z score, cardiac valve function, corneal clouding, and visual acuity in 35 patients with attenuated mucopolysaccharidosis type I (Hurler-Scheie and Scheie syndromes) for up to 10 years following the initiation of laronidase therapy.

RESULTS

Statistically significant (P < .001) reductions in mean urinary glycosaminoglycan levels relative to baseline were observed 6 months after treatment initiation and were sustained throughout follow-up. Disease remained stable after treatment initiation with no statistically significant changes in mean FVC, 6MWT, or height-for-age Z score. At last assessments, mitral and aortic valve function remained stable in 65% (22/34) of patients; corneal clouding remained stable in 78% (18/23); visual acuity remained stable in 33% (8/24) and improved in 42% (10/24) of patients. Younger patients (<10 years at treatment initiation) maintained disease measures closer to norms for age for FVC, 6MWT, and height and showed fewer deteriorations in mitral and aortic valve disease and corneal clouding compared with patients aged ≥10 years at treatment initiation.

CONCLUSION

Laronidase treatment resulted in disease stabilization in the majority of patients with a mean follow-up of 6.1 years. Data suggest that early treatment may result in better outcomes.

Receiving enzyme replacement therapy for a lysosomal storage disorder: a preliminary exploration of the experiences of young patients and their families

Medical intervention for lysosomal storage disorders becomes part of life, shaping the reality of the condition for affected individuals and families. Enzyme replacement therapy (ERT) is available to treat some lysosomal storage disorders. ERT is costly and time consuming, requiring frequent hospital visits to receive intravenous infusions. This qualitative study sought to explore the impact of receiving ERT for a lysosomal storage disorder on the health related quality of life (HRQoL) of young patients and their families. Fifteen semi-structured interviews were conducted with young people and parents and siblings of young people accessing ERT for Pompe disease, Gaucher disease or mucopolysaccharidosis types I or II living in Victoria, Australia. Interviews were transcribed then analyzed thematically. The biopsychosocial model assisted in interpreting themes. Findings revealed positive attitudes towards ERT, with noticed improvements in physical and psychosocial well-being. Participants prioritised intervention over other activities and provided suggestions for improving current service delivery. Communication with family members and professionals was deemed important, especially in respect to information provision. Participants described challenges associated with living with a lysosomal storage disorder and receiving ERT and coping strategies, such as positive thinking and ways to manage uncertainty. These findings provide valuable insights into the impact of living with a chronic genetic condition and receiving intensive treatment on HRQoL.