Health utilities and quality of life in individuals with tuberous sclerosis complex (TSC) who experience epileptic seizures: A web-based survey.

OBJECTIVES: Individuals with tuberous sclerosis complex (TSC) experience a wide range of health impacts, including epileptic seizures, negatively impacting their health-related quality of life (HRQoL). Health state utility values (HSUVs) are index values representing HRQoL and are used as key inputs for health economic analyses. Such data are currently very limited in the TSC population. The objective of this study was to generate HSUVs for TSC health states, defined by the number and type of seizures experienced in the previous week, and to compare with UK normative values. METHODS: This cross-sectional study involved 186 participants (individuals with TSC = 61, caregivers reporting for individuals with TSC = 125) from Europe and North America who completed a web-based survey. Participants completed the [EuroQol - 5 dimensions - 3 levels] (self-report version for individuals with TSC or proxy version 1 for caregivers). RESULTS: The mean age of individuals with TSC was 27.3 years (self-reported: 41.3 years, caregiver-reported: 20.5 years); 56% were males. Most individuals with TSC (71%) reported experiencing between one and ten seizures in the week prior to participating in the study. The most frequently reported type of seizure was focal: simple partial (50%). Across all participants (combined self-report and caregiver-report), the mean HSUV was 0.474 (95% confidence interval [CI]: 0.424-0.524), significantly lower than the UK norm (0.856, 95%CI: 0.848-0.864) [1]. Mean HSUV and HRQoL scores were consistently lower when reported by caregivers than when self-reported by individuals with TSC (HSUV = 0.351 vs. 0.727). This is in part because caregivers reported for individuals with TSC who experienced more frequent and severe seizures than those who were able to self-report. HSUVs incrementally decreased with the experience of more frequent (1-5 per week: HSUV = 0.666 vs. >20: HSUV = 0.290) and more severe seizures (focal: simple partial: HSUV = 0.450 vs. generalized: convulsive: HSUV = 0.194). CONCLUSIONS: The HRQoL and HSUV index scores indicate substantial impairment among individuals with TSC; HSUVs were shown to decrease considerably with increases in seizure frequency or seizure severity, indicating that more burdensome seizure health states are associated with poorer HRQoL.

Determining the pathogenicity of patient-derived TSC2 mutations by functional characterization and clinical evidence.

Tuberous sclerosis complex (TSC) is a genetic condition characterized by the growth of benign tumours in multiple organs, including the brain and kidneys, alongside intellectual disability and seizures. Identification of a causative mutation in TSC1 or TSC2 is important for accurate genetic counselling in affected families, but it is not always clear from genetic data whether a sequence variant is pathogenic or not. In vitro functional analysis could provide support for determining whether an unclassified TSC1 or TSC2 variant is disease-causing. We have performed a detailed functional analysis of four patient-derived TSC2 mutations, E92V, R505Q, H597R and L1624P. One mutant, E92V, functioned similarly to wild-type TSC2, whereas H597R and L1624P had abnormal function in all assays, consistent with available clinical and segregation information. One TSC2 mutation, R505Q, was identified in a patient with intellectual disability, seizures and autistic spectrum disorder but who did not fulfil the diagnostic criteria for TSC. The R505Q mutation was also found in two relatives, one with mild learning difficulties and one without apparent phenotypic abnormality. R505Q TSC2 exhibited partially disrupted function in our assays. These data highlight the difficulties of assessing pathogenicity of a mutation and suggest that multiple lines of evidence, both genetic and functional, are required to assess the pathogenicity of some mutations.