Tuberous sclerosis associated neuropsychiatric disorders (TAND) and the TAND Checklist

Coexistence of Autism Spectrum Disorders Among Three Children with Tuberous Sclerosis Complex: Case reports and review of literature

Tuberous sclerosis complex (TSC) is a multisystem neurocutaneous disorder inherited in an autosomal dominant manner and characterised by benign tumours in the brain and other vital organs such as the heart, eyes, kidneys, skin and lungs. Links between autism spectrum disorder (ASD) and TSC have been postulated for many decades, with TSC considered to be one of the main syndromic causes of ASD; however, precise confirmation of a relationship between these two disorders required validated diagnostic tools. Fortunately, accurate evaluation of this relationship is now possible with standardised criteria for ASD diagnosis. We report three children who presented to the Sultan Qaboos University Hospital, Muscat, Oman, between 2014 and 2015 with ASD and TSC. These cases demonstrate the spectrum of neuropsychiatric involvement in TSC and highlight the importance of screening children with TSC for ASD features in order to encourage the early enrolment of these children in educational and rehabilitation programmes.

[ESPED-Survey: TSC-disease in children and adolescents: preliminary results from a German epidemiological survey]

BACKGROUND

Tuberous sclerosis complex (TSC) disease is a rare genetic, multi-organ disorder characterized by the occurrence of multiple hamartoma.

METHODS

In cooperation with ESPED, Germany, a prospective, epidemiological study was performed to assess the incidence of newly diagnosed TSC disease in patients ≤18 years in Germany. Moreover, the following parameters were assessed: 1. Age distribution at initial diagnosis; 2. Percentage of patients with in utero diagnosis of TSC; 3. Detailed description of pathological clinical findings; 4. Results from genetic testing.

RESULTS

In this one-year interim analysis, 84 electronic questionnaires were received, 17 of which did not contain complete sets of data and were not included in data analysis. Twenty-three of 67 questionnaires did not report TSC patients and 3 reports contained redundant data sets and were excluded. In total, 41 reports were included into data analysis (female: 23; male: 18); median age at first diagnosis was 6 months (range: 0-151 months). The three most common symptoms were: central nervous affection: 31/41 patients ((75.6 %); 29/31 with seizures); rhabdomyoma: in 20/41 (48.8 %); cutaneous affection: hypomelanotic maculae ("white spots"): 20/41 (48.8 %). The three following organ manifestations were seen most often in a comprehensive diagnostic work-up: rhabdomyoma: 23/41 ((56.1 %); cortical dysplasia: 22/41 (53.7 %); "white spots"): 20/41 (48.8 %). In 11/41 patients, cardiac rhabdomyoma were detected by ultrasonography prenatally. In 6 patients, a TSC-2 mutation was found while in 4 patients a TSC-1 mutation was noted; in 1 patient, genetic testing was negative.

CONCLUSIONS

Based on our preliminary findings, the annual incidence rate for TSC disease is estimated at approximately 1:12,300 live births, but this is a very rough approximation.

Applying the Lessons of Tuberous Sclerosis: The 2015 Hower Award Lecture

Tuberous sclerosis complex is a dominantly inherited disorder that variably affects the brain, skin, kidneys, heart, and other organs. Its neurological manifestations include epilepsy, autism, cognitive and behavioral dysfunction, and giant cell tumors. A mutation of either TSC1 or TSC2 can cause tuberous sclerosis complex. Their two gene products, hamartin and tuberin, form a physical complex which normally inhibits protein synthesis mediated through the mechanistic target of rapamycin, so a TSC1 or TSC2 mutation results in overactivation of the mechanistic target of rapamycin cascade. In addition to their tumor suppressor roles, TSC1 and TSC2 help to regulate cell size, neuronal migration, axon formation, and synaptic plasticity. Clinical trials of two different the mechanistic target of rapamycin inhibitors have demonstrated substantial improvement of tuberous sclerosis complex-related tumors, and a recent trial also showed a benefit from the mechanistic target of rapamycin inhibitor everolimus in the treatment of refractory epilepsy due to tuberous sclerosis complex. Effective mechanism-based therapy is now available for some manifestations of tuberous sclerosis complex.

Ungual fibroma in 12-year-old boy with hypomelanotic macules, intellectual disability and attention deficit hyperactivity disorder-possible tuberous sclerosis

Objective:

To report a case of a 12-year-old boy with intellectual disability and attention deficit hyperactivity disorder, who came to surgery for an examination due to a minor bulge on the left thumb, which had been growing for the previous month. His mother denied any trauma.

Methods:

After the removal of the clinically ambiguous bulge and a pathohistological confirmation that it was a periungual fibroma, complete patient analysis was performed due to the presence of hypomelanotic macules and a suspected tuberous sclerosis.

Results:

Considering the presence of hypomelanotic macules, as one of the main criteria, possible TS diagnosis was set.

Conclusion:

Early detection of the symptoms of TS enables a timely provision of protocols for further patient monitoring, which affects the patient’s morbidity and mortality.

The use of everolimus in the treatment of neurocognitive problems in tuberous sclerosis (TRON): study protocol for a randomised controlled trial

Background

Tuberous sclerosis complex (TSC) is a genetic disorder affecting about 1 in 6000 people and is characterised by the development of tumours in many organs, including the skin and kidneys, and by a range of neurological and neuropsychiatric manifestations. TSC-associated neuropsychiatric disorders (TAND) occur in the majority of those with TSC, and they have a significant impact on patients and their families, given the everyday impact of TAND on education, employment, family and social life. The potential benefits of better treatment for TAND therefore include reduction in health care demands and wider benefits for patients and their carers.

Methods/design

We have planned a single-centre, two-arm, individually randomised, phase II, double-blind, placebo-controlled trial of everolimus versus placebo in the treatment of neurocognitive problems in patients with tuberous sclerosis. Everolimus is a licensed medicine in this patient group, but for a different target of effect. The present trial is a proof-of-principle study developed to provide effect size estimates which may be used to inform the design of subsequent trials. Forty-eight patients aged 16–60 years with tuberous sclerosis who have an IQ >60 and a significant deficit (at least −2 SD) in one or more primary outcome measures will be randomly allocated in a ratio of 2:1 to receive everolimus or placebo, respectively. Participants will be assessed for eligibility and then be started on study medication 4 weeks later. They will then be randomised and receive placebo or everolimus for 24 weeks. Neurocognitive and safety assessments will be carried out at baseline and weeks 4, 12, 24 and 36.

Discussion

This study is designed to determine the effect sizes of treatment with everolimus or placebo for 6 months on specific neurocognitive functions—recall memory (verbal and non-verbal) and executive function—in people affected by TSC who have significant deficits in these functions. These data will provide new evidence to determine whether larger-scale trials are indicated and to explore suitable outcome measures and analytical methods for neurocognitive trial design.

Trial registration

ISRCTN09739757. Registered on 28 Dec 2011.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1446-6) contains supplementary material, which is available to authorized users.

Whole Exome Sequencing Identifies TSC1/TSC2 Biallelic Loss as the Primary and Sufficient Driver Event for Renal Angiomyolipoma Development

Renal angiomyolipoma is a kidney tumor in the perivascular epithelioid (PEComa) family that is common in patients with Tuberous Sclerosis Complex (TSC) and Lymphangioleiomyomatosis (LAM) but occurs rarely sporadically. Though histologically benign, renal angiomyolipoma can cause life-threatening hemorrhage and kidney failure. Both angiomyolipoma and LAM have mutations in TSC2 or TSC1. However, the frequency and contribution of other somatic events in tumor development is unknown. We performed whole exome sequencing in 32 resected tumor samples (n = 30 angiomyolipoma, n = 2 LAM) from 15 subjects, including three with TSC. Two germline and 22 somatic inactivating mutations in TSC2 were identified, and one germline TSC1 mutation. Twenty of 32 (62%) samples showed copy neutral LOH (CN-LOH) in TSC2 or TSC1 with at least 8 different LOH regions, and 30 of 32 (94%) had biallelic loss of either TSC2 or TSC1. Whole exome sequencing identified a median of 4 somatic non-synonymous coding region mutations (other than in TSC2/TSC1), a mutation rate lower than nearly all other cancer types. Three genes with mutations were known cancer associated genes (BAP1, ARHGAP35 and SPEN), but they were mutated in a single sample each, and were missense variants with uncertain functional effects. Analysis of sixteen angiomyolipomas from a TSC subject showed both second hit point mutations and CN-LOH in TSC2, many of which were distinct, indicating that they were of independent clonal origin. However, three tumors had two shared mutations in addition to private somatic mutations, suggesting a branching evolutionary pattern of tumor development following initiating loss of TSC2. Our results indicate that TSC2 and less commonly TSC1 alterations are the primary essential driver event in angiomyolipoma/LAM, whereas other somatic mutations are rare and likely do not contribute to tumor development.

We performed comprehensive genome analysis of a kidney tumor called angiomyolipoma. These tumors are known to develop in most individuals who have Tuberous Sclerosis Complex (TSC) and those who have sporadic lymphangioleiomyomatosis (LAM), and are seen rarely in the general population. In these angiomyolipomas, we found consistent involvement of the TSC2 and TSC1 genes that are known to cause TSC, but very few (<5 on average) mutations elsewhere in the protein-coding regions. This is in stark contrast to other adult solid tumours that typically harbor hundreds to thousands of such mutations. Our results indicate that genetic alterations in TSC2/TSC1 are the primary and essential driver genetic events for development and progression of renal angiomyolipoma. Analysis of multiple angiomyolipomas from a single patient showed distinct genetic aberrations in the majority of samples, indicating that most of the tumors had developed independently. Branched clonal evolution was evident from the observation of three tumors that shared 2 mutations in addition to mutations private to each. Our results indicate that therapeutic approaches for treatment of patients with angiomyolipoma should focus on the consequences of TSC2/TSC1 loss, including but not limited to mTOR activation.

Symptom profiles of autism spectrum disorder in tuberous sclerosis complex

OBJECTIVE

To determine the extent to which deficits associated with autism spectrum disorder (ASD) in toddlers with tuberous sclerosis complex (TSC) overlap with those in toddlers with nonsyndromic ASD (nsASD) and to examine cognitive function and epilepsy severity in toddlers with TSC and comorbid ASD. This is the endpoint analysis from a longitudinal investigation of ASD risk factors in children with TSC.

METHODS

Measures included the Autism Diagnostic Observation Schedule (ADOS), the Mullen Scales of Early Learning, and clinical epilepsy variables. A repeated-measures analysis of variance was performed with between-subjects factor of group (typically developing, TSC/no ASD, TSC/ASD, nsASD) and within-subjects factors of individual ADOS item scores in the social communication and repetitive behavior/restricted interest domains. Within the TSC group, comparisons of epilepsy characteristics and cognitive domains were performed using independent-samples t tests.

RESULTS

Children with TSC/ASD demonstrated a profile of social communication impairment that had complete convergence with nsASD. Measured social communication impairments included gestures, pointing, eye contact, responsive social smile, and shared enjoyment. This convergence was observed despite the high comorbidity between ASD and cognitive impairment in TSC.

CONCLUSIONS

This study supports the clinical diagnosis of ASD in young children with TSC and demonstrates remarkable convergence of autism symptoms between TSC/ASD and nsASD. Our results strongly suggest the need for early intervention in toddlers with TSC, with treatment strategies targeting social communication function as well as broader developmental domains, before the onset of autism symptoms.

Advances and Future Directions for Tuberous Sclerosis Complex Research: Recommendations From the 2015 Strategic Planning Conference

On March 10 to March 12, 2015, the National Institute of Neurological Disorders and Stroke and the Tuberous Sclerosis Alliance sponsored a workshop in Bethesda, Maryland, to assess progress and new opportunities for research in tuberous sclerosis complex with the goal of updating the 2003 Research Plan for Tuberous Sclerosis (http://www.ninds.nih.gov/about_ninds/plans/tscler_research_plan.htm). In addition to the National Institute of Neurological Disorders and Stroke and Tuberous Sclerosis Alliance, participants in the strategic planning effort and workshop included representatives from six other Institutes of the National Institutes of Health, the Department of Defense Tuberous Sclerosis Complex Research Program, and a broad cross-section of basic scientists and clinicians with expertise in tuberous sclerosis complex along with representatives from the pharmaceutical industry. Here we summarize the outcomes from the extensive premeeting deliberations and final workshop recommendations, including (1) progress in the field since publication of the initial 2003 research plan for tuberous sclerosis complex, (2) the key gaps, needs, and challenges that hinder progress in tuberous sclerosis complex research, and (3) a new set of research priorities along with specific recommendations for addressing the major challenges in each priority area. The new research plan is organized around both short-term and long-term goals with the expectation that progress toward specific objectives can be achieved within a five to ten year time frame.

Tuberous sclerosis complex-associated renal angiomyolipomas: A single center study of 17 consecutive cases

The aim of the present study was to investigate the treatment options for patients with tuberous sclerosis complex (TSC)-associated renal angiomyolipomas (AMLs). A total of 17 patients who were consecutively diagnosed with TSC-associated renal AMLs at the Department of Urology of Zhongshan Hospital between 1998 and 2012 were included in the study. The patient cohort included 7 males and 10 females with a mean age of 37.6 years (range, 18-62 years). A total of 12 patients were diagnosed with renal AML with TSC during physical examination (PE), while 5 patients were admitted to the Emergency Department of Zhongshan Hospital due to spontaneous rupture of renal AMLs. All renal lesions were examined by ultrasonography and abdominal computed tomography prior to treatment. The primary outcome measure was the kidney reservation rate (patients that had not received nephrectomies) in the rupture group and PE group. Both abdominal ultrasonography and CT revealed AMLs in all patients and the mean tumor size was 10.0±4.0 cm (range, 3.0-17.5 cm). Overall, 9 patients underwent surgery, which included unilateral nephrectomy in 4 patients and unilateral partial nephrectomy/tumor enucleation in 5 patients. The remaining 8 patients received medical treatment. All patients were followed-up for between 10 and 67 months. One patient succumbed as a result of multiple organ failure, which was caused by hypovolemic shock due to the spontaneous rupture of renal AML. The kidney reservation rate during surgery was 87.5% (7/8) in the PE group and 25% (1/4) in the spontaneous rupture group. The management of TSC-associated renal AMLs differs from that of solitary sporadic AMLs. Surgical therapy is recommended following careful risk-benefit analysis.

Tuberous sclerosis complex: Five new things

Purpose of review

Tuberous sclerosis complex (TSC) is a variably expressed neurocutaneous genetic disorder characterized by hamartomatous growths in multiple organ systems. Neurologic involvement often confers the most severe symptoms, and can include epilepsy, increased intracranial pressure from hydrocephalus, intellectual deficits, and autism. The purpose of this review is to provide a neurologically focused update in the diagnosis and treatment of these complications in patients with TSC.

Recent findings

We highlight 5 new areas of understanding in TSC: the neurobiology of TSC and its translation into clinical practice, vigabatrin in the treatment of infantile spasms, the role of tubers and epilepsy surgery, the treatment of subependymal giant cell astrocytomas, and TSC-related neuropsychiatric disorders.

Summary

These recent advances in diagnosis and treatment give our patients with TSC and their families hope for the future for improved care and possible preventive cures, to the end goal of improving quality of life.

Tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder that affects multiple organ systems and is caused by loss-of-function mutations in one of two genes: TSC1 or TSC2. The disorder can affect both adults and children. First described in depth by Bourneville in 1880, it is now estimated that nearly 2 million people are affected by the disease worldwide. The clinical features of TSC are distinctive and can vary widely between individuals, even within one family. Major features of the disease include tumours of the brain, skin, heart, lungs and kidneys, seizures and TSC-associated neuropsychiatric disorders, which can include autism spectrum disorder and cognitive disability. TSC1 (also known as hamartin) and TSC2 (also known as tuberin) form the TSC protein complex that acts as an inhibitor of the mechanistic target of rapamycin (mTOR) signalling pathway, which in turn plays a pivotal part in regulating cell growth, proliferation, autophagy and protein and lipid synthesis. Remarkable progress in basic and translational research, in addition to several randomized controlled trials worldwide, has led to regulatory approval of the use of mTOR inhibitors for the treatment of renal angiomyolipomas, brain subependymal giant cell astrocytomas and pulmonary lymphangioleiomyomatosis, but further research is needed to establish full indications of therapeutic treatment. In this Primer, we review the state-of-the-art knowledge in the TSC field, including the molecular and cellular basis of the disease, medical management, major knowledge gaps and ongoing research towards a cure.

Tuberous Sclerosis Australia: a case study of a maturing patient-driven organisation

Purpose

– Tuberous Sclerosis Australia (TSA) is a small rare disease organisation with a large scope. TSA was established in 1981 as a peer support organisation. Since then, its role has evolved to meet the needs of its members: individuals living with tuberous sclerosis complex (TSC), their families and health professionals. The paper aims to discuss these issues.

Design/methodology/approach

– This case study describes the diverse activities of TSA which include, but are not limited to: the provision of information and support services; sponsorship of research and fostering a network of TSC health professionals. The benefits of collaborations forged under the umbrella organisation TSC International are highlighted.

Findings

– The case study demonstrates some of the key challenges TSA faces, challenges shared by many similar health charities. These include: funding of health education and promotion activities; working with a large range of health professionals and the challenge of research fatigue.

Originality/value

– There is little research published describing the work of small disease specific organisations similar to TSA. This case study provides insight for those collaborating with similar organisations including health professionals and researchers.

Advances in Tuberous Sclerosis Complex (TSC) research

Purpose

– The purpose of this paper is to provide a brief, descriptive overview of Tuberous Sclerosis Complex (TSC) research with particular reference to studies on Autism Spectrum Disorder (ASD).

Design/methodology/approach

– A search of electronic databases was carried out to identify English language articles on TSC. The literature was explored in more detail with a focus on neurodevelopmental disorders associated with TSC such as ASD.

Findings

– The review included 3,679 references. The earliest articles identified were published in the early twentieth century. Since then research on TSC has advanced rapidly and is being carried out worldwide. Just 62 studies have focused on ASD in TSC, although the number of publications is increasing over time.

Research limitations/implications

– More research on ASD in TSC is needed to benefit those affected by TSC and the broader ASD scientific community.

Practical implications

– Practitioners working with children and adults with ASD should be aware of the wider health issues experienced by those with genetic conditions such as TSC. Similarly, clinicians working with those who have TSC should be aware of the high prevalence of ASD in the group and implications for the way they work with their patients.

Originality/value

– This is the first paper to map and characterise the scientific literature on TSC. There remains a focus on the biomedical aspects of TSC with fewer studies on psychosocial/educational or family impacts. The review concludes with recommended research questions for the future.

Towards an improved understanding of TSC-Associated Neuropsychiatric Disorders (TAND)

Purpose

– Tuberous Sclerosis Complex (TSC) is associated with many learning, behavioural, neurodevelopmental and psychiatric difficulties. Over 90 per cent of those with TSC will have some of these concerns, yet typically no more than 20 per cent receive support and treatment. The purpose of this paper is to provide an overview of TSC-Associated Neuropsychiatric Disorders (TAND), explore barriers to identification and management of TAND, and propose possible next steps to improve assessment and treatment of TAND.

Design/methodology/approach

– The paper combines a brief review of the multiple levels of TAND with a conceptual analysis of barriers and potential facilitators to assessment and intervention for TAND.

Findings

– Results suggest that the perceived uniqueness of TAND leads to treatment paralysis for most healthcare professionals, thus explaining the assessment and treatment gap seen for TAND. This may in part be due to the multi-dimensionality of TAND, and in part due to lack of access to clear, useful and evidence-based resources for TAND.

Research limitations/implications

– Identification of natural TAND clusters through machine-based learning and data reduction methodologies may yield a manageable number of natural groups of TSC-related neuropsychiatric problems, for which a basic “toolkit” of evidence-based interventions could be developed.

Practical implications

– Families and clinicians will benefit from a toolkit of tried and tested resources and evidence-based information to guide further investigation and management of TAND.

Originality/value

– Even though individuals will have unique TAND profiles, there may be key natural TAND clusters – combinations of behaviours across multi-dimensional levels – that will simplify and improve access to further evaluation, treatment and neuroscientific research.

The impact of tuberous sclerosis complex – a parent’s perspective

Purpose

– The purpose of this paper is to describe the impact of having a child with tuberous sclerosis complex (TSC).

Design/methodology/approach

– The author explains the process her family has been through on their TSC journey.

Findings

– Several themes emerge from the author’s story: a lack of awareness about relatively common conditions such as epilepsy; a dearth of accessible information provided to families; delays in identification/assessment and a lack of follow up on parents’ concerns; the wide range in the quality of advice provided from one professional/service to another; the extent to which parents have to advocate for their children and the importance of social support.

Originality/value

– Few journal articles explore the impact of complex health conditions on families from their perspective and in their own words. This thought provoking viewpoint piece provides a powerful insight into the reality of having a child with TSC.

Early developmental pathways to autism spectrum disorder in tuberous sclerosis complex

Purpose

– Tuberous sclerosis complex (TSC) is a genetic disorder with a high prevalence of autism spectrum disorder (ASD), yet no single genetic, neurological or neurophysiological risk marker is necessary or sufficient to increase risk for ASD. This paper aims to discuss the utility of adopting a developmental perspective.

Design/methodology/approach

– The increasing number of TSC infants presenting with abnormalities prenatally provides a unique opportunity to study risk pathways to ASD from birth. Here, the authors review findings to date that support the investigation of infants with TSC to further our understanding of typical and atypical development.

Findings

– Evidence has accumulated from studies of infants at familial risk for ASD (“baby siblings”) to suggest that early markers of ASD are present in the first year of life. The early waves of prospective studies of infants with TSC indicate dynamic changes in developmental trajectories to ASD and are likely to provide insight into cascading effects of brain “insult” early in development. Emerging evidence of phenotypic and biological homology between syndromic and idiopathic cases of ASD supports the notion of a convergence of risk factors on a final common pathway in ASD.

Originality/value

– The delineation of brain-based biomarkers of risk, prediction and treatment response in TSC will be critical in aiding the development of targeted intervention and prevention strategies for those infants at high risk of poorer developmental outcomes.

Cross-sectional Imaging Review of Tuberous Sclerosis

Tuberous sclerosis complex (TSC) is a multisystem, genetic disorder characterized by development of hamartomas in the brain, abdomen, and thorax. It results from a mutation in one of 2 tumor suppressor genes that activates the mammalian target of rapamycin pathway. This article discusses the origins of the disorder, the recently updated criteria for the diagnosis of TSC, and the cross-sectional imaging findings and recommendations for surveillance. Familiarity with the diverse radiological features facilitates diagnosis and helps in treatment planning and monitoring response to treatment of this multisystem disorder.

Profile of everolimus in the treatment of tuberous sclerosis complex: an evidence-based review of its place in therapy

Tuberous sclerosis complex (TSC) is a relatively rare genetic disorder, affecting one in 6,000 births. Mammalian target of rapamycin (mTOR) inhibitors, such as everolimus, which have been previously used to prevent solid organ transplant rejection, augment anticancer treatment regimens, and prevent neovascularization of artificial cardiac stents, are now approved for treating TSC-related manifestations, such as subependymal giant cell astrocytomas and renal angiomyolipomas. The use of everolimus in treating subependymal giant cell astrocytomas is supported by long-term Phase II and III clinical trials. Seizures are a common feature in TSC, occurring in up to 96% of patients. While mTOR inhibitors currently do not have regulatory approval in treating this manifestation, small clinical studies have demonstrated beneficial outcomes with everolimus. Further evidence from a forthcoming Phase III clinical study may provide additional support for the use of everolimus for this indication. Also, there are no approved treatments for TSC-associated neuropsychiatric disorders, which include intellectual disability, behavioral difficulties, and autism spectrum disorder, but preclinical data and small studies have suggested that some neuropsychiatric symptoms may be improved through mTOR inhibition therapy. More evidence is needed, particularly regarding safety in young infants. This review focuses on the current evidence supporting the use of everolimus in neurologic and neuropsychiatric manifestations of TSC, and the place of everolimus in therapy.

mTOR, a Potential Target to Treat Autism Spectrum Disorder

Mammalian target of rapamycin (mTOR) is a key regulator in various cellular processes, including cell growth, gene expression, and synaptic functions. Autism spectrum disorder (ASD) is frequently accompanied by monogenic disorders, such as tuberous sclerosis complex, phosphatase and tensin homolog tumor hamartoma syndrome, neurofibromatosis 1, and fragile X syndrome, in which mTOR is hyperactive. Mutations in the genes involved in the mTOR-mediated signaling pathway have been identified in some cases of syndromic ASD. Evidences indicate a pathogenic role for hyperactive mTOR-mediated signaling in ASD associated with these monogenic disorders, and mTOR inhibitors are a potential pharmacotherapy for ASD. Abnormal synaptic transmission through metabotropic glutamate receptor 5 may underlie in a part of ASD associated with hyperactive mTOR-mediated signaling. In this review, the relationship between mTOR and ASD is discussed.

Autism and the synapse: emerging mechanisms and mechanism-based therapies

PURPOSE OF REVIEW

Recent studies have implicated hundreds of genetic variants in the cause of autism spectrum disorder (ASD). Genes involved in 'monogenic' forms of syndromic ASD converge on common pathways that are involved in synaptic development, plasticity and signaling. In this review, we discuss how these 'developmental synaptopathies' inform our understanding of the molecular disease in ASD and highlight promising approaches that have bridged the gap between the bench and the clinic.

RECENT FINDINGS

Accumulating evidence suggests that synaptic deficits in syndromic and nonsyndromic ASD can be mapped to gene mutations in pathways that control synaptic protein synthesis and degradation, postsynaptic scaffold architecture and neurotransmitter receptors. This is recapitulated in models of Fragile X syndrome (FXS), Tuberous Sclerosis Complex (TSC), Angelman syndrome and Phelan-McDermid syndrome (PMS), all of which cause syndromic ASD. Important recent advances include the development of mouse models and patient-derived induced pluripotent stem cell (iPSC) lines that enable a detailed investigation of synaptic deficits and the identification of potential targets for therapy. Examples of the latter include mGluR5 antagonists in FXS, mTOR inhibitors in TSC and insulin-like growth factor 1 (IGF-1) in PMS.

SUMMARY

Identifying converging pathways in syndromic forms of ASD will uncover novel therapeutic targets for non-syndromic ASD. Insights into developmental synaptopathies will lead to rational development of mechanism-based therapies and clinical trials that may provide a blueprint for other common pathways implicated in the molecular neuropathology of ASD.

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.

Genotype/Phenotype Correlations in Tuberous Sclerosis Complex

Tuberous sclerosis complex (TSC) is an autosomal dominant disorder characterized by the development of widespread hamartomatous lesions in various organs, including brain, skin, kidneys, heart, and eyes. Central nervous system is almost invariably involved, with up to 85% of patients presenting with epilepsy, and at least half of patients having intellectual disability or other neuropsychiatric disorders including autism spectrum disorder. TSC is caused by the mutation in one of the 2 genes TSC1, at 9q34, and TSC2, at 16p13.3. They respectively encode for hamartin and tuberin, which form an intracellular complex inhibiting the mammalian target of rapamycin. Mammalian target of rapamycin overactivation following the genetic defect determines the cell growth and proliferation responsible for TSC-related lesions, as well as the alterations in neuronal excitability and synaptogenesis leading to epilepsy and neuropsychiatric disorders. A causative mutation for the disorder is identified in about 85% of patients with a clinical diagnosis of TSC. Mosaicism and technology limits likely explain most of the no mutation identified cases. This review confirms that patients with TSC2 mutations considered as a group usually present a more severe phenotype, characterized by higher number of tubers, earlier age at seizure onset and higher prevalence of intellectual disability. However, the clinical phenotype of the disease presents a high variability, thus making the prediction of the phenotype on an individual basis still challenging. The increasing application of new molecular techniques to subjects with TSC has the potential to significantly reduce the rate of patients with no mutation demonstrated and to identify an increasing higher number of mutations. This would hopefully allow a better characterization of higher risk mutations, which might help clinicians to plan individualized surveillance plans. Furthermore, the increasing availability of disease registries to collect clinical and genetics data of patients help to define more valid and clinically oriented genotype or phenotype correlations.

Neurological and neuropsychiatric aspects of tuberous sclerosis complex

Tuberous sclerosis (also known as tuberous sclerosis complex [TSC]) is a multisystem genetic disorder that affects almost every organ in the body. Mutations in the TSC1 or TSC2 genes lead to disruption of the TSC1-TSC2 intracellular protein complex, causing overactivation of the mammalian target of rapamycin (mTOR) protein complex. The surveillance and management guidelines and clinical criteria for tuberous sclerosis were revised in 2012, and mTOR inhibitors are now recommended as treatment options for subependymal giant cell astrocytomas and renal angiomyolipomas-two common features of the disease. However, most morbidity and mortality caused by tuberous sclerosis is associated with neurological and neuropsychiatric manifestations. Treatment of epilepsy associated with tuberous sclerosis remains a major challenge, with more than 60% of patients having ongoing seizures. Tuberous-sclerosis-associated neuropsychiatric disorders (TAND) are multilevel and occur in most individuals with the disorder, but are rarely assessed and treated. Clinical trials of mTOR inhibitors to treat seizures and TAND are underway. Management of the neurological and neuropsychiatric manifestations of the disorder should be coordinated with treatment of other organ systems. In view of the age-related expression of manifestations from infancy to adulthood, continuity of clinical care and ongoing monitoring is paramount, and particular attention is needed to plan transition of patient care from childhood to adult services.

Tuberous Sclerosis: A New Frontier in Targeted Treatment of Autism

Tuberous sclerosis complex (TSC) is a genetic disorder with a high prevalence of autism spectrum disorder (ASD). Tremendous progress in understanding the pathogenesis of TSC has been made in recent years, along with initial trials of medical treatment aimed specifically at the underlying mechanism of the disorder. At the cellular level, loss of TSC1 or TSC2 results in upregulation of the mechanistic target of rapamycin (mTOR) pathway. At the circuitry level, TSC and mTOR play crucial roles in axonal, dendritic, and synaptic development and function. In this review, we discuss the molecular mechanism underlying TSC, and how this disease results in aberrant neural connectivity at multiple levels in the central nervous system, leading to ASD symptoms. We then review recent advances in mechanism-based treatments of TSC, and the promise that these treatments provide for future mechanism-based treatment of ASD. Because of these recent advances, TSC represents an ideal model for how to make progress in understanding and treating the mechanisms that underlie ASD in general.

Advances in the treatment of tuberous sclerosis complex

PURPOSE OF REVIEW

Tuberous sclerosis complex (TSC) is a multisystem genetic disorder with physical and neuropsychiatric manifestations and significant research progress has been made in recent years. Here, we focus on the key advances over the last 18 months.

RECENT FINDINGS

Three main themes were identified in the literature. Firstly, the diagnostic criteria and surveillance guidelines for TSC were revised, incorporating a genetic criterion alongside clinical criteria, and making a positive step towards evidence-based treatment of TSC. Secondly, a new term - TSC-associated neuropsychiatric disorders (TAND) - was introduced as an umbrella term for all possible neuropsychiatric difficulties seen in TSC, and a TAND Checklist was developed as a screening tool. Thirdly, the risks and benefits of molecularly targeted treatments of the neuropsychiatric manifestations of TSC are being debated.

SUMMARY

The updated diagnostic criteria and management guidelines, the new concept of TAND and the TAND Checklist should lead to significant improvements in the quality of care for individuals with TSC. The promise of mammalian target of rapamycin inhibitors and other molecular treatments are still to be confirmed. We suggest that great care should be taken to identify 'optimal mammalian target of rapamycin signalling' in the therapeutic approach to the neuropsychiatric features of the disorder.

Tuberous sclerosis complex

Tuberous sclerosis complex (TSC) is a neurocutaneous syndrome that can affect the brain, skin, eyes, kidneys, heart, and lungs. TSC alters cellular proliferation and differentiation, resulting in hamartomas of various organs, tumor formation, and altered neuronal migration. The phenotype is highly variable. Most individuals have seizures, commonly including infantile spasms, and there is variable intellectual disability and autism. Neonates can present with cardiac failure due to intracardiac rhabdomyomas. The likelihood of renal angiomyolipomas increases with age, and renal disease is the most common cause of death in adults with TSC. Pulmonary involvement occurs predominantly in women and carries a high morbidity and mortality. TSC is inherited as an autosomal dominant trait, but spontaneous mutations are common. A mutation of either TSC1 on chromosome 9 or TSC2 on chromosome 16 leads to dysfunction of hamartin or tuberin, respectively. These two proteins form a functional complex that modulates the mammalian target of rapamycin (mTOR) pathway. Medications that inhibit mTOR are being used to treat TSC-related tumors, and current studies are investigating whether these agents could alleviate other TSC complications. Consensus statements guide identification and optimal management of many of the TSC-related complications at diagnosis and throughout the lifespan. A multidisciplinary approach is necessary for optimal management of individuals with TSC.