A novel KCNC1 gain-of-function variant causing developmental and epileptic encephalopathy: "Precision medicine" approach with fluoxetine.

Variable phenotypes, including developmental encephalopathy with (DEE) or without seizures and myoclonic epilepsy and ataxia due to potassium channel mutation, are caused by pathogenetic variants in KCNC1, encoding for Kv3.1 channel subunits. In vitro, channels carrying most KCNC1 pathogenic variants display loss-of-function features. Here, we describe a child affected by DEE with fever-triggered seizures, caused by a novel de novo heterozygous missense KCNC1 variant (c.1273G>A; V425M). Patch-clamp recordings in transiently transfected CHO cells revealed that, compared to wild-type, Kv3.1 V425M currents (1) were larger, with membrane potentials between -40 and +40 mV; (2) displayed a hyperpolarizing shift in activation gating; (3) failed to inactivate; and (4) had slower activation and deactivation kinetics, consistent with a mixed functional pattern with prevalent gain-of-function effects. Exposure to the antidepressant drug fluoxetine inhibited currents expressed by both wild-type and mutant Kv3.1 channels. Treatment of the proband with fluoxetine led to a rapid and prolonged clinical amelioration, with the disappearance of seizures and an improvement in balance, gross motor skills, and oculomotor coordination. These results suggest that drug repurposing based on the specific genetic defect may provide an effective personalized treatment for KCNC1-related DEEs.

Epilepsy in adult patients with tuberous sclerosis complex.

OBJECTIVES: Little is known about the evolution of epilepsy in individuals with tuberous sclerosis complex (TSC) in adulthood. This study aims at describing the characteristics of epilepsy in adult TSC patients attending a single multidisciplinary clinic. MATERIALS AND METHODS: We collected data about epilepsy (age at onset, seizure types, history of infantile spasms (IS), epilepsy diagnosis and outcome), genetic and neuroradiological findings, cognitive outcome and psychiatric comorbidities. RESULTS: Out of 257 adults with TSC, 183 (71.2%) had epilepsy: 121 (67.2%) were drug-resistant; 59 (32.8%) seizure-free, at a median age of 18 years. 22% of the seizure-free patients (13/59) discontinued medication. Median age at seizure onset was 9 months. Seventy-six patients (41.5%) had a history of IS. TSC2 pathogenic variants (p = 0.018), cortical tubers (p < 0.001) and subependymal nodules (SENs) (p < 0.001) were more frequent in those who developed epilepsy. Cognitive functioning was lower (p < 0.001) and psychiatric disorders more frequent (p = 0.001). We did not find significant differences regarding age, gender, mutation and tubers/SENs in seizure-free vs drug-resistant individuals. Intellectual disability (p < 0.001) and psychiatric disorders (p = 0.004) were more common among drug-resistant patients. CONCLUSIONS: Epilepsy in TSC can be a lifelong disorder, but one-third of individuals reach seizure freedom by early adulthood. In the long term, age at epilepsy onset has a crucial role in drug resistance and in developing intellectual disability, both in drug-resistant and drug-sensible patients. Patients with drug-refractory seizures tend to develop psychiatric issues, which should be recognized and adequately treated.

Tuberous sclerosis complex (TSC), lymphangioleiomyomatosis, and COVID-19: The experience of a TSC clinic in Italy.

Individuals with comorbidities are at higher risk of coronavirus disease 2019 (COVID-19) and worse outcome, but little information has been available about patients with genetic diseases and COVID-19. This study aims at evaluating the presence and outcome of COVID-19 in a cohort of Italian patients with tuberous sclerosis complex (TSC) and/or lymphangioleiomyomatosis (LAM), and at reviewing the possible effects of mTOR inhibitors on SARS-CoV-2 infection. We included 102 unselected individuals with a diagnosis of TSC and/or LAM assessed between January 1, 2020 and April 24, 2020 (29% children, 71% adults). Twenty-six patients were on mTOR inhibitors. Demographic data, TSC manifestations, presence, and outcomes in individuals with confirmed or suspected SARS-CoV-2 infection were evaluated. Health status and outcomes of all patients on mTOR inhibitors were assessed. One patient with severe TSC had polymerase chain reaction (PCR)-confirmed SARS-CoV-2 infection, was admitted to ICU, and died. Nine additional patients either met the definition of suspect case or presented with at least two of the most common symptoms of SARS-CoV-2 infection. All recovered fully. None of the patients treated with mTOR inhibitors for their underlying comorbidities was diagnosed with COVID-19, and those who showed suspicious respiratory symptoms recovered fully. This cohort study provides preliminary information on COVID-19 in people with TSC in Italy and suggests feasibility to systematically evaluate the role of mTOR inhibitors in SARS-CoV-2 infection.

Gabapentin treatment in a patient with KCNQ2 developmental epileptic encephalopathy.

De novo variants in KCNQ2 encoding for Kv7.2 voltage-dependent neuronal potassium (K+) channel subunits are associated with developmental epileptic encephalopathy (DEE). We herein describe the clinical and electroencephalographic (EEG) features of a child with early-onset DEE caused by the novel KCNQ2 p.G310S variant. In vitro experiments demonstrated that the mutation induces loss-of-function effects on the currents produced by channels incorporating mutant subunits; these effects were counteracted by the selective Kv7 opener retigabine and by gabapentin, a recently described Kv7 activator. Given these data, the patient started treatment with gabapentin, showing a rapid and sustained clinical and EEG improvement over the following months. Overall, these results suggest that gabapentin can be regarded as a precision therapy for DEEs due to KCNQ2 loss-of-function mutations.

Autism spectrum disorder in tuberous sclerosis complex: searching for risk markers.

BACKGROUND: Neuropsychiatric disorders are present in up to 90% of patients with Tuberous Sclerosis Complex (TSC), and represent an important issue for families. Autism Spectrum Disorder (ASD) is the most common neurobehavioral disease, affecting up to 61% of patients. The aims of this study were: 1) to assess the prevalence of ASD in a TSC population; 2) to describe the severity of ASD; 3) to identify potential risk factors associated with the development of ASD in TSC patients. METHODS: We selected 42 individuals over age 4 years with a definite diagnosis of TSC and followed at a TSC clinic in Northern Italy. We collected and reported clinical and genetic data, as well as cognitive level, for each of them. We administered the Social Communication Questionnaire (SCQ) as a reliable screening tool for ASD, and performed comparisons between the average scores and each clinical and genetic feature. RESULTS: Seventeen out of 42 patients (40.5%) had a score at the SCQ suggestive of ASD (≥15 points). When calculated for each cognitive level category, the average SCQ score tended to be progressively higher in patients with a worse cognitive level, and the number of pathological SCQ scores increased with worsening of intellectual disability. With respect to ASD severity, the scores were equally distributed, indicating that the degree of ASD in TSC patients may have a large variability. By comparing the average SCQ scores with the clinical features, we found statistically significant correlations with epilepsy, seizure onset before age one year, spasms, mutations in TSC2, cognitive level, sleep disorders, and other psychiatric problems, but not with seizure frequency, tubers localization and gender. CONCLUSIONS: Our study showed a prevalence of ASD of 40.5%, confirming the higher risk for this disorder in patients with TSC. However, the severity seems to have a notable variability in TSC patients. Risk factors for ASD are epilepsy, infantile spams, and mutations in TSC2.