Genetic and phenotypic spectrum associated with IFIH1 gain-of-function.

IFIH1 gain-of-function has been reported as a cause of a type I interferonopathy encompassing a spectrum of autoinflammatory phenotypes including Aicardi-Goutières syndrome and Singleton Merten syndrome. Ascertaining patients through a European and North American collaboration, we set out to describe the molecular, clinical and interferon status of a cohort of individuals with pathogenic heterozygous mutations in IFIH1. We identified 74 individuals from 51 families segregating a total of 27 likely pathogenic mutations in IFIH1. Ten adult individuals, 13.5% of all mutation carriers, were clinically asymptomatic (with seven of these aged over 50 years). All mutations were associated with enhanced type I interferon signaling, including six variants (22%) which were predicted as benign according to multiple in silico pathogenicity programs. The identified mutations cluster close to the ATP binding region of the protein. These data confirm variable expression and nonpenetrance as important characteristics of the IFIH1 genotype, a consistent association with enhanced type I interferon signaling, and a common mutational mechanism involving increased RNA binding affinity or decreased efficiency of ATP hydrolysis and filament disassembly rate.

Long-term Outcome of Allogeneic Hematopoietic Stem Cell Transplantation in Patients With Juvenile Metachromatic Leukodystrophy Compared With Nontransplanted Control Patients.

IMPORTANCE: Allogeneic hematopoietic stem cell transplantation (HSCT) has been the only treatment option clinically available during the last 20 years for juvenile metachromatic leukodystrophy (MLD), reported with variable outcome and without comparison with the natural course of the disease. OBJECTIVE: To compare the long-term outcome of patients who underwent allogeneic HSCT with control patients who did not among a cohort with juvenile MLD. DESIGN, SETTING, AND PARTICIPANTS: Patients with juvenile MLD born between 1975 and 2009 and who received HSCT at a median age of 7 years (age range, 1.5-18.2 years) and nontransplanted patients with juvenile MLD born between 1967 and 2007 were included in this case-control study. The median follow-up after HSCT was 7.5 years (range, 3.0-19.7 years). Patients underwent HSCT at 3 German centers between 1991 and 2012. The analysis was done between July 2014 and August 2015. MAIN OUTCOMES AND MEASURES: Survival and transplantation-related mortality, loss of gross motor function (Gross Motor Function Classification in MLD), loss of any language function, and magnetic resonance imaging (MRI) severity score for cerebral changes. To explore prognostic factors at baseline, patients who underwent HSCT (hereafter, transplanted patients) were a priori divided into stable vs progressive disease, according to gross motor and cognitive function. RESULTS: Participants were 24 transplanted patients (11 boys, 13 girls) and 41 control patients (22 boys, 19 girls) who did not receive transplantation (hereafter, nontransplanted patients) with juvenile MLD. Among the transplanted patients, 4 children died of transplantation-related mortality, and 2 additional children died of rapid MLD progression 1.5 and 8.6 years after HSCT, resulting in a 5-year survival of 79% (19 of 24). Among the nontransplanted patients, 5-year survival after disease onset was 100% (41 of 41). However, 11 died of MLD progression, resulting in similar overall survival within the observation period. Nine of the long-term survivors after HSCT had disease progression, while 11 showed stable disease. Compared with the nontransplanted patients, the transplanted patients were less likely to lose their gross motor or language function and demonstrated significantly lower MRI severity scores at the latest examination. Patients after HSCT were more likely to have a stable disease course when undergoing HSCT at an early stage with no or only mild gross motor deficits (Gross Motor Function Classification in MLD level 0 or 1) and an IQ of at least 85, when age at disease onset was older than 4 years, or when MRI severity scores were low (preferably ≤17). CONCLUSIONS AND RELEVANCE: Among patients with juvenile MLD, patients who underwent HSCT had a better gross motor and language outcome and lower MRI severity scores compared with nontransplanted patients. Transplantation at a presymptomatic or early symptomatic stage of juvenile MLD is associated with a reasonable chance for disease stabilization.

Natural history of infantile G(M2) gangliosidosis.

OBJECTIVE: G(M2) gangliosidoses are caused by an inherited deficiency of lysosomal ß-hexosaminidase and result in ganglioside accumulation in the brain. Onset during infancy leads to rapid neurodegeneration and death before 4 years of age. We set out to quantify the rate of functional decline in infantile G(M2) gangliosidosis on the basis of patient surveys and a comprehensive review of existing literature. METHODS: Patients with infantile G(M2) gangliosidosis (N = 237) were surveyed via questionnaire by the National Tay Sachs & Allied Diseases Association (NTSAD). These data were supplemented by survival data from the NTSAD database and a literature survey. Detailed retrospective surveys from 97 patients were available. Five patients who had received hematopoietic stem cell transplantation were evaluated separately. The mortality rate of the remaining 92 patients was comparable to that of the 103 patients from the NTSAD database and 121 patients reported in the literature. RESULTS: Common symptoms at onset were developmental arrest (83%), startling (65%), and hypotonia (60%). All 55 patients who had learned to sit without support lost that ability within 1 year. Individual functional measures correlated with each other but not with survival. Gastric tube placement was associated with prolonged survival. Tay Sachs and Sandhoff variants did not differ. Hematopoietic stem cell transplantation was not associated with prolonged survival. CONCLUSIONS: We studied the timing of regression in 97 cases of infantile G(M2) gangliosidosis and conclude that clinical disease progression does not correlate with survival, likely because of the impact of improved supportive care over time. However, functional measures are quantifiable and can inform power calculations and study design of future interventions.