Down Syndrome Disintegrative Disorder: New-Onset Autistic Regression, Dementia, and Insomnia in Older Children and Adolescents With Down Syndrome

Down Syndrome and Autoimmune Disease

Down syndrome is the most common genetic cause of intellectual disability and has previously been associated with a variety of autoimmune disorders affecting multiple organ systems. The high prevalence of autoimmune disease, in conjunction with other inflammatory and infectious diseases, in this population suggests an intrinsic immune dysregulation associated with triplication of chromosome 21. Emerging data on the role of chromosome 21 in interferon activation, cytokine production, and activation of B-cell mediated autoimmunity are emerging hypotheses that may explain the elevated prevalence of autoimmune thyroid disease, celiac disease, type I diabetes, autoimmune skin disease, and a variety of autoimmune neurologic conditions. As the life expectancy for individuals with Down syndrome increases, knowledge of the epidemiology, clinical features, management and underlying causes of these conditions will become increasingly important. Disorders such as Hashimoto's thyroiditis are prevalent in between 13 and 34% of individuals with Down syndrome but only 3% of the neurotypical population, a pattern similarly recognized in individuals with Celiac Disease (5.8% v 0.5-2%), alopecia areata (27.7% v. 2%), and vitiligo (4.4% v. 0.05-1.55%), respectively. Given the chronicity of autoimmune conditions, early identification and management can significantly impact the quality of life of individuals with Down syndrome. This comprehensive review will highlight common clinical autoimmune conditions observed in individuals with Down syndrome and explore our current understanding of the mechanisms of disease in this population.

De novo variants in immune regulatory genes in Down syndrome regression disorder

BACKGROUND

Down Syndrome Regression Disorder (DSRD) is a rare and poorly understood disorder of the central nervous system, characterized by acute or subacute neuropsychiatric symptoms in previously healthy individuals with Down syndrome (DS). Many patients exhibit immunotherapy-responsiveness, indicative of immune dysregulation as a potential underlying etiology. While hypotheses are emerging regarding the role of interferon signaling in DSRD and other autoimmune conditions associated with DS, it is unclear why a small subset of individuals with DS develop DSRD. The aim of this study was to investigate genes of immune regulation in persons with DSRD.

METHODS

This study included individuals with DSRD aged 10-30 years with trio exome sequencing performed during the diagnostic work up. Descriptive statistics and univariate analysis (Chi-square and Fisher's exact test) were used to describe and compare the characteristics of individuals with and without variants.

RESULTS

Forty-one individuals with DSRD had trio exome sequencing results. Eight (20%) had heterozygous de novo variants of immune regulatory genes, with four variants being pathogenic or likely pathogenic (UNC13D, XIAP, RNASEH2A, and DNASE1L3). All genes harboring pathogenic variants were associated with interferon type-1 inflammatory response. Individuals harboring variants were more likely to have a preceding trigger (p = 0.03, 95% CI 1.21-97.06), rapid clinical decline in less than 1 month (p = 0.01, 95% CI 1.67-52.06), and MRI abnormalities (p < 0.001, 95% CI 4.89-527.71).

DISCUSSION

A distinct subset of individuals with DSRD exhibited pathogenic variants in immune regulation genes associated with interferon-mediated inflammatory response, coinciding with previously established links between these genes and interferonopathies such as Aicardi-Goutieres syndrome. Our observations suggest that these variants might potentially contribute to the development of DSRD in individuals with DS.

Safety and tolerability of intravenous immunoglobulin infusion in Down syndrome regression disorder

Three large multi-center studies have identified the clinical utility of intravenous immunoglobulin (IVIg) in the treatment of Down syndrome regression disorder (DSRD). Yet the tolerability of infusions in individuals with DS and the safety of IVIg remains unknown in this population. This study sought to evaluate the safety and tolerability of IVIg in individuals with DSRD compared to a real-world cohort of individuals with pediatric onset neuroimmunologic disorders. A single-center, retrospective chart review evaluating clinically documented infusion reactions was performed for individuals meeting international consensus criteria for DSRD and having IVIg infusions between 2019 and 2023. Infusion reactions were evaluated for severity and need for alterations in infusion plan. This cohort was compared against an age and sex matched cohort of children with neuroimmunologic conditions who had also received IVIg infusions. In total, 127 individuals with DSRD and 186 individuals with other neuroimmunologic disorders were enrolled. There was no difference in the overall rate of adverse reactions (AEs) between the DSRD and general neuroimmunology cohorts (p = 0.31, 95% CI: 0.80-2.00), but cardiac-related AEs specifically were more common among the DSRD group (p = 0.02, 95% CI: 1.23-17.54). When AEs did occur, there was no difference in frequency of pharmacologic intervention (p = 0.12, 95% CI: 0.34-1.13) or discontinuation of therapy (p = 0.74, 95% CI: 0.06-7.44). There was a higher incidence of lab abnormalities on IVIG among the general neuroimmunology cohort (p = 0.03, 95% CI: 0.24-0.94) compared to the DSRD cohort. Transaminitis was the most common laboratory abnormality in the DSRD group. In a large cohort of individuals with DSRD, there were no significant differences in the safety and tolerability of IVIg compared to a cohort of children and young adults with neuroimmunologic conditions.

Neuroimaging abnormalities associated with immunotherapy responsiveness in Down syndrome regression disorder

OBJECTIVE

To determine the prevalence of neuroimaging abnormalities in individuals with Down syndrome regression disorder (DSRD) and evaluate if neuroimaging abnormalities were predictive of therapeutic responses.

METHODS

A multicenter, retrospective, case-control study which reviewed neuroimaging studies of individuals with DSRD and compared them to a control cohort of individuals with Down syndrome (DS) alone was performed. Individuals aged 10-30 years and meeting international consensus criteria for DSRD were included. The presence of T1, T2/FLAIR, and SWI signal abnormalities was reviewed. Response rates to various therapies, including immunotherapy, were evaluated in the presence of neuroimaging abnormalities.

RESULTS

In total, 74 individuals (35%) had either T2/FLAIR and/or SWI signal abnormality compared to 14 individuals (12%) without DSRD (p < 0.001, 95%CI: 2.18-7.63). T2/FLAIR signal abnormalities were not appreciated more frequently in individuals with DSRD (14%, 30/210) than in the control cohort (9%, 11/119) (p = 0.18, OR: 1.63, 95%CI: 0.79-3.40). SWI signal abnormalities were appreciated at a higher frequency in individuals with DSRD (24%, 51/210) compared to the control cohort (4%, 5/119) (p < 0.001, OR: 7.31, 95%CI: 2.83-18.90). T2/FLAIR signal abnormalities were localized to the frontal (40%, 12/30) and parietal lobes (37%, 11/30). SWI signal abnormalities were predominantly in the bilateral basal ganglia (94%, 49/52). Individuals with DSRD and the presence of T2/FLAIR and/or SWI signal abnormalities were much more likely to respond to immunotherapy (p < 0.001, OR: 8.42. 95%CI: 3.78-18.76) and less likely to respond to benzodiazepines (p = 0.01, OR: 0.45, 95%CI: 0.25-0.83), antipsychotics (p < 0.001, OR: 0.28, 95%CI: 0.11-0.55), or electroconvulsive therapy (p < 0.001, OR: 0.12; 95%CI: 0.02-0.78) compared to individuals without these neuroimaging abnormalities.

INTERPRETATION

This study indicates that in individuals diagnosed with DSRD, T2/FLAIR, and SWI signal abnormalities are more common than previously thought and predict response to immunotherapy.

Insomnia Symptoms Are Associated with Measures of Functional Deterioration and Dementia Status in Adults with Down Syndrome at High Risk for Alzheimer's Disease

Background

While obstructive sleep apnea (OSA) and insomnia symptoms in neurotypical populations are associated with Alzheimer's disease (AD), their association with dementia in adults with Down syndrome (DS) remains less clear, even though these symptoms are prevalent and treatable in DS. Understanding their associations with AD-related dementia status, cognitive impairment, and functional deterioration may lead to interventions to slow decline or disease progression in adults with DS.

Objective

To characterize differences in OSA and insomnia symptom expression by dementia status, and to determine which sleep factors support dementia diagnosis.

Methods

Multimodal consensus conference was used to determine dementia status in 52 adults with DS (52.2 ± 6.4 years, 21 women). Cognitive impairment, adaptive behavior skills, and symptoms of OSA and insomnia were quantified using validated assessments for adults with DS and their primary informants.

Results

A sex by dementia status interaction demonstrated that older women with DS and dementia had more severe terminal insomnia but not OSA symptoms relative to older women with DS who were cognitively stable (CS). Greater insomnia symptom severity was associated with greater functional impairments in social and self-care domains adjusting for age, sex, premorbid intellectual impairment, and dementia status.

Conclusions

Insomnia symptoms are more severe in women with DS with dementia than in women with DS and no dementia, and regardless of dementia status or sex, more severe insomnia symptoms are associated with greater impairment in activities of daily living. These findings underscore the potential importance of early insomnia symptom evaluation and treatment in women with DS at risk of developing AD.

Psychopharmacological treatments in Down syndrome and autism spectrum disorder: State of the research and practical considerations

Individuals with Down syndrome (DS) or Autism Spectrum Disorder (ASD), and especially those with both DS and co-occurring ASD (DS + ASD) commonly display behavioral and psychiatric symptoms that can impact quality of life and places increased burden on caregivers. While the mainstay of treatment in DS and ASD is focused on educational and behavioral therapies, pharmacological treatments can be used to reduce symptom burden. There is a paucity of evidence and limited clinical trials in DS and DS + ASD. Some scientific evidence is available, primarily in open label studies and case series that can guide treatment choices. Additionally, clinical decisions are often extrapolated from evidence and experience from those with ASD, or intellectual disability in those without DS. This article reviews current research in pharmacological treatment in DS, ASD, and DS + ASD, reviews co-occurring neurodevelopmental and mental health diagnoses in individuals with DS + ASD across the lifespan, and describes practical approaches to psychopharmacological management.

Genomic architecture of autism spectrum disorder in Qatar: The BARAKA-Qatar Study

BACKGROUND

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by impaired social and communication skills, restricted interests, and repetitive behaviors. The prevalence of ASD among children in Qatar was recently estimated to be 1.1%, though the genetic architecture underlying ASD both in Qatar and the greater Middle East has been largely unexplored. Here, we describe the first genomic data release from the BARAKA-Qatar Study-a nationwide program building a broadly consented biorepository of individuals with ASD and their families available for sample and data sharing and multi-omics research.

METHODS

In this first release, we present a comprehensive analysis of whole-genome sequencing (WGS) data of the first 100 families (372 individuals), investigating the genetic architecture, including single-nucleotide variants (SNVs), copy number variants (CNVs), tandem repeat expansions (TREs), as well as mitochondrial DNA variants (mtDNA) segregating with ASD in local families.

RESULTS

Overall, we identify potentially pathogenic variants in known genes or regions in 27 out of 100 families (27%), of which 11 variants (40.7%) were classified as pathogenic or likely-pathogenic based on American College of Medical Genetics (ACMG) guidelines. Dominant variants, including de novo and inherited, contributed to 15 (55.6%) of these families, consisting of SNVs/indels (66.7%), CNVs (13.3%), TREs (13.3%), and mtDNA variants (6.7%). Moreover, homozygous variants were found in 7 families (25.9%), with a sixfold increase in homozygous burden in consanguineous versus non-consanguineous families (13.6% and 1.8%, respectively). Furthermore, 28 novel ASD candidate genes were identified in 20 families, 23 of which had recurrent hits in MSSNG and SSC cohorts.

CONCLUSIONS

This study illustrates the value of ASD studies in under-represented populations and the importance of WGS as a comprehensive tool for establishing a molecular diagnosis for families with ASD. Moreover, it uncovers a significant role for recessive variation in ASD architecture in consanguineous settings and provides a unique resource of Middle Eastern genomes for future research to the global ASD community.

Behavioural sleep problems in children and adults with intellectual disabilities: An integrative literature review

BACKGROUND

People with intellectual disabilities are more likely to experience sleep problems, which can affect quality of life, physical health, mental health and well-being.

METHODS

An integrative literature review was conducted to investigate what is known about behavioural sleep disturbances in people with an intellectual disability. The search used the following databases: Scopus, PsycInfo and Cinahl, to find papers published since 2015.

RESULTS

Within intellectual disability research, sleep appears as a common issue due to its high prevalence, negative relationships with an individual's physical and mental health, their quality of life, and impact of sleep problems on family or carers. The growing evidence base appears to support the use of behavioural, lifestyle and pharmacological interventions to improve sleep in people with an intellectual disability.

CONCLUSION

A wide array of literature provides evidence that people with intellectual disabilities are affected by and need support with their sleep.

Alternative Diagnoses in the Work Up of Down Syndrome Regression Disorder

PURPOSE

Down Syndrome Regression Disorder (DSRD) is a diagnosis of exclusion. Psychiatric and neuroimmunologic etiologies have been proposed although the exact etiology remains unknown. This study sought to review non-DSRD diagnoses at a large quaternary medical center specializing in the diagnosis of DSRD and compare clinical characteristics between those diagnosed with DSRD and those with non-DSRD diagnoses.

METHODS

The authors performed a single-center retrospective, chart-based, review of referrals for developmental regression in individuals with Down syndrome.

RESULTS

Two hundred and sixty-six individuals were evaluated for DSRD and of these, 54 (20%) ultimately had alternative diagnoses. Individuals with DSRD were more likely to have shorter nadir to clinical symptoms (p = 0.01, 95% CI: 0.36-0.47) and have preceding triggers (p < 0.001, 95% CI: 1.13-1.43) compared to those with alternative diagnoses. Individuals with non-DSRD diagnoses were more likely to be born premature (p = 0.01, 95% CI: 0.51-0.87) and have a history of epilepsy (p = 0.01, 95% CI: 0.23-0.77) but were also less likely to have a history of cytokine abnormalities on bloodwork (p < 0.001, 95% CI: 1.19-1.43) and have catatonia (p < 0.001, 95% CI: 1.54-2.17). The majority of alternative diagnoses (41/54, 76%) were autism spectrum disorder. In these cases, symptoms were more likely to be longstanding (symptoms > 12 months) and earlier onset (median 8 years, IQR: 6-11). Other diagnoses included epilepsy (5/54, 9%), Celiac disease (5/54, 9%), cerebrovascular disease (3/54, 6%).

CONCLUSIONS

This study identifies that 20% of individuals referred with concerns for DSRD have alternative diagnoses. The majority of these diagnoses were autism, but rare treatable conditions were also identified, highlighting the importance of a thorough neurodiagnostic assessment.

Immunotherapy responsiveness and risk of relapse in Down syndrome regression disorder

Down syndrome regression disorder (DSRD) is a clinical symptom cluster consisting of neuropsychiatric regression without an identifiable cause. This study evaluated the clinical effectiveness of IVIg and evaluated clinical characteristics associated with relapse after therapy discontinuation. A prospective, multi-center, non-randomized, observational study was performed. Patients met criteria for DSRD and were treated with IVIg. All patients underwent a standardized wean-off therapy after 9-12 months of treatment. Baseline, on-therapy, and relapse scores of the Neuropsychiatric Inventory Total Score (NPITS), Clinical Global Impression-Severity (CGI-S), and the Bush-Francis Catatonia Rating Scale (BFCRS) were used to track clinical symptoms. Eighty-two individuals were enrolled in this study. Patients had lower BFCRS (MD: -6.68; 95% CI: -8.23, -5.14), CGI-S (MD: -1.27; 95% CI: -1.73, -0.81), and NPITS scores (MD: -6.50; 95% CI: -7.53, -5.47) while they were on therapy compared to baseline. Approximately 46% of the patients (n = 38) experienced neurologic relapse with wean of IVIg. Patients with neurologic relapse were more likely to have any abnormal neurodiagnostic study (χ2 = 11.82, P = 0.001), abnormal MRI (χ2 = 7.78, P = 0.005), and abnormal LP (χ2 = 5.45, P = 0.02), and a personal history of autoimmunity (OR: 6.11, P < 0.001) compared to patients without relapse. IVIg was highly effective in the treatment of DSRD. Individuals with a history of personal autoimmunity or neurodiagnostic abnormalities were more likely to relapse following weaning of immunotherapy, indicating the potential for, a chronic autoimmune etiology in some cases of DSRD.

Case report: Evolution of catatonic mutism and psychotic symptoms in an adolescent with Down syndrome: transition from Down syndrome disintegrative disorder to anti-N-methyl-D-aspartate receptor encephalitis

During her first year of junior high school, a 12-year-old Japanese girl with Down syndrome experienced dizziness, gait disruption, paroxysmal weakness in her hands, and sluggish speaking. Regular blood tests and a brain MRI revealed no abnormalities, and she was tentatively diagnosed with adjustment disorder. Nine months later, the patient experienced a subacute sickness of chest pain, nausea, sleep problem with night terrors, and delusion of observation. Rapid deterioration then developed with simultaneous fever, akinetic mutism, loss of facial expression, and urine incontinence. These catatonic symptoms improved after a few weeks after admission and treatment with lorazepam, escitalopram, and aripiprazole. After discharge, nonetheless, daytime slumber, empty eyes, paradoxical laughter, and declined verbal communication persisted. Upon confirmation of the cerebrospinal N-methyl-D-aspartate (NMDA) receptor autoantibody, methylprednisolone pulse therapy was tried, but it had little effect. Visual hallucinations and cenesthopathy, as well as suicidal thoughts and delusions of death, have predominated in the following years. Cerebrospinal IL-1ra, IL-5, IL-15, CCL5, G-CSF, PDGFbb, and VFGF were raised in the early stage of initial medical attention with nonspecific complaints, but were less prominent in the later stages of catatonic mutism and psychotic symptoms. We suggest a disease concept of progression from Down syndrome disintegrative disorder to NMDA receptor encephalitis, based on this experience.

Down syndrome regression disorder: updates and therapeutic advances

PURPOSE OF REVIEW

Down syndrome regression disorder (DSRD) is a symptom cluster consisting of neuropsychiatric regression without cause. Although knowledge of this condition has accelerated over the last decade, prior studies have been limited by heterogenous nomenclature, diagnostic approaches and therapeutic interventions. This review highlights recent advances in the diagnosis and clinical approach to DSRD and reviews the most up-to-date literature on therapeutic interventions for this condition.

RECENT FINDINGS

Several multicentre studies have reported exciting findings on the presence of neurodiagnostic study abnormalities and responses to a variety of therapeutics, including psychotropics (including benzodiazepines), electroconvulsive therapy and immunotherapy. Differential response rates have been observed in the presence and absence of a variety of clinical and diagnostic factors.

SUMMARY

Individuals with DSRD are responsive to a variety of psychiatric pharmacotherapy and immunotherapy underscoring this phenotype may have multiple causes. Multidisciplinary care is helpful in the evaluation and management of individuals with this condition.

Immunotherapy Responsiveness and Risk of Relapse in Down Syndrome Regression Disorder

Down syndrome regression disorder (DSRD) is a clinical symptom cluster consisting of neuropsychiatric regression without an identifiable cause. This study evaluated the clinical effectiveness of IVIg and evaluated clinical characteristics associated with relapse after therapy discontinuation. A prospective, multi-center, non-randomized, observational study was performed. Patients met criteria for DSRD and were treated with IVIg. All patients underwent a standardized wean off therapy after 9-12 months of treatment. Baseline, on therapy, and relapse scores of the Neuropsychiatric Inventory Total Score (NPITS), Clinical Global Impression-Severity (CGI-S), and the Bush-Francis Catatonia Rating Scale (BFCRS) were used to track clinical symptoms. Eighty-two individuals were enrolled in this study. Patients had lower BFCRS (MD: -6.68; 95% CI: -8.23, -5.14), CGI-S (MD: -1.27; 95% CI: -1.73, -0.81), and NPITS scores (MD: -6.50; 95% CI: -7.53, -5.47) while they were on therapy compared to baseline. Approximately 46% of the patients (n = 38) experienced neurologic relapse with wean of IVIg. Patients with neurologic relapse were more likely to have any abnormal neurodiagnostic study (χ2 = 11.82, p = 0.001), abnormal MRI (χ2 = 7.78, p = 0.005), and abnormal LP (χ2 = 5.45, p = 0.02), and a personal history of autoimmunity (OR: 6.11, p < 0.001) compared to patients without relapse. IVIg was highly effective in the treatment of DSRD. Individuals with a history of personal autoimmunity or neurodiagnostic abnormalities were more likely to relapse following weaning of immunotherapy, indicating the potential for, a chronic autoimmune etiology in some cases of DSRD.

Down syndrome regression disorder, a case series: Clinical characterization and therapeutic approaches

Down syndrome (DS) is one of the most frequent genetic disorders and represents the first cause of intellectual disability of genetic origin. While the majority of patients with DS follow a harmonious evolution, an unusual neurodevelopmental regression may occur, distinct from that described in the context of autism spectrum disorders, called down syndrome regression disorder (DSRD). Based on four patients, two males and two females, with age range between 20 and 24, treated at the Reference Center for Rare Psychiatric Disorders of the GHU Paris Psychiatry and Neurosciences [Pôle hospitalo-universitaire d'Évaluation Prévention et Innovation Thérapeutique (PEPIT)], we describe this syndrome, discuss its etiologies and propose therapeutic strategies. DSRD often occurs in late adolescence. There is a sudden onset of language disorders, loss of autonomy and daily living skills, as well as behavioral symptoms such as depression, psychosis, or catatonia. These symptoms are non-specific and lead to an overlap with other diagnostic categories, thus complicating diagnosis. The etiologies of the syndrome are not clearly identified but certain predispositions of patients with trisomy 21 have suggested an underlying immune-mediated mechanism. Symptomatic therapeutic approaches (serotonergic antidepressants, atypical antipsychotics, benzodiazepines) were not effective, and generally associated with poor tolerance. Etiological treatments, including anti-inflammatory drugs and corticosteroids, led to partial or good recovery in the four cases. Early recognition of regressive symptoms and rapid implementation of adapted treatments are required to improve the quality of life of patients and their families.

Abnormal Brain Iron Accumulation is a Rare Finding in Down Syndrome Regression Disorder

BACKGROUND

Down syndrome regression disorder (DSRD) is characterized by the sudden loss of adaptive function, cognitive-executive function, and language with abnormal sleep and/or motor control.

METHODS

Clinical, laboratory, and imaging data from three individuals with DSRD and iron on brain imaging were reviewed.

RESULTS

Three patients with Down syndrome presented with new onset of flat affect, depression, reduced speech, and other neurological symptoms consistent with DSRD. Magnetic resonance imaging showed abnormal iron accumulation in the basal ganglia, as well as calcification in two cases. Molecular diagnostic testing for neurodegeneration with brain iron accumulation was negative in the two individuals tested.

CONCLUSIONS

These individuals presented suggest that a subset of individuals with DSRD have abnormal brain iron accumulation. Motor control symptoms reported in DSRD, such as stereotypies and parkinsonism, may reflect this basal ganglia involvement. The presence of abnormal brain iron should not delay or preclude diagnosis and treatment for DSRD.

Unexplained regression in Down syndrome: Management of 51 patients in an international patient database

Research to guide clinicians in the management of the devastating regression which can affect adolescents and young adults with Down syndrome is limited. A multi-site, international, longitudinal cohort of individuals with a clinical diagnosis of Unexplained Regression in Down syndrome (URDS) was collated through seven Down syndrome clinics. Tiered medical evaluation, a 28-item core symptom list, and interim management are described naturalistically. Improvement-defined by the percentage of baseline function on a Parent-reported Functional Score, overall improvement in symptoms on a Clinician-administered Functional Assessment, or report of management type being associated with improvement-was analyzed. Improvement rates using ECT, IVIG, and others were compared. Across seven clinics, 51 patients with URDS had regression at age 17.6 years, on average, and showed an average 14.1 out of 28 symptoms. Longitudinal improvement in function was achieved in many patients and the medical management, types of treatment, and their impact on function are described. Management with intravenous immunoglobulin (IVIG) was significantly associated with higher rate of improvement in symptoms at the next visit (p = 0.001). Our longitudinal data demonstrates that URDS is treatable, with various forms of clinical management and has a variable course. The data suggests that IVIG may be an effective treatment in some individuals. Our description of the management approaches used in this cohort lays the groundwork for future research, such as development of standardized objective outcome measure and creation of a clinical practice guideline for URDS.

Assessment and Diagnosis of Down Syndrome Regression Disorder: International Expert Consensus

Objective

To develop standardization for nomenclature, diagnostic work up and diagnostic criteria for cases of neurocognitive regression in Down syndrome.

Background

There are no consensus criteria for the evaluation or diagnosis of neurocognitive regression in persons with Down syndrome. As such, previously published data on this condition is relegated to smaller case series with heterogenous data sets. Lack of standardized assessment tools has slowed research in this clinical area.

Methods

The authors performed a two-round traditional Delphi method survey of an international group of clinicians with experience in treating Down syndrome to develop a standardized approach to clinical care and research in this area. Thirty-eight potential panelists who had either previously published on neurocognitive regression in Down syndrome or were involved in national or international working groups on this condition were invited to participate. In total, 27 panelists (71%) represented nine medical specialties and six different countries reached agreement on preliminary standards in this disease area. Moderators developed a proposed nomenclature, diagnostic work up and diagnostic criteria based on previously published reports of regression in persons with Down syndrome.

Results

During the first round of survey, agreement on nomenclature for the condition was reached with 78% of panelists agreeing to use the term Down Syndrome Regression Disorder (DSRD). Agreement on diagnostic work up and diagnostic criteria was not reach on the first round due to low agreement amongst panelists with regards to the need for neurodiagnostic testing. Following incorporation of panelist feedback, diagnostic criteria were agreed upon (96% agreement on neuroimaging, 100% agreement on bloodwork, 88% agreement on lumbar puncture, 100% agreement on urine studies, and 96% agreement on "other" studies) as were diagnostic criteria (96% agreement).

Conclusions

The authors present international consensus agreement on the nomenclature, diagnostic work up, and diagnostic criteria for DSRD, providing an initial practical framework that can advance both research and clinical practices for this condition.

Evidence of neuroinflammation and immunotherapy responsiveness in individuals with down syndrome regression disorder

Background

Down syndrome regression disorder is a symptom cluster consisting of neuropsychiatric regression without cause. This study evaluated the incidence of neurodiagnostic abnormalities in individuals with Down syndrome regression disorder and determined if abnormalities are indicative of responses to therapeutic intervention.

Methods

A retrospective, multi-center, case-control study was performed. Patients were required to have subacute onset and the presence of four of five symptom groups present (cognitive decline, expressive language, sleep derangement, loss of ability to perform activities of daily living, and/or a new movement disorder) and no other explanation for symptoms.

Results

Individuals with Down syndrome regression disorder were comparable to a cohort of individuals with only Down syndrome although had higher rates of autoimmune disease (p = 0.02, 95%CI 1.04–1.75). Neurodiagnostic abnormalities were found on EEG (n = 19, 26%), neuroimaging (n = 16, 22%), and CSF (n = 9, 17%). Pleocytosis was appreciated in five cases, elevated total protein in nine, elevated IgG index in seven, and oligoclonal bands in two. Testing within 2 years of symptom onset was more likely to have neurodiagnostic abnormalities (p = 0.01, 95%CI 1.64–37.06). In individuals with neurodiagnostic abnormalities, immunotherapy was nearly four times more likely to have a therapeutic effect than in those without neurodiagnostic abnormalities (OR 4.11, 95%CI 1.88–9.02). In those with normal neurodiagnostic studies (n = 43), IVIg was effective in 14 of 17 (82%) patients as well although other immunotherapies were uniformly ineffective.

Conclusions

This study reports the novel presence of neurodiagnostic testing abnormalities in individuals with Down syndrome regression disorder, providing credence to this symptom cluster potentially being of neurologic and/or neuroimmunologic etiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11689-022-09446-w.

[Regression in Young Adults with Down-Syndrome: A Case Series]

BACKGROUND

Regression in young adults with Down syndrome can present itself with an acute loss of acquired skills and change in behavior. The aim of our case series was to describe the heterogeneous clinical presentation of this syndrome as well as accompanying diagnostic and therapeutic challenges and consequences.

METHODS

All three patients were assessed with the CAMDEX-DS (Cambridge Examination for Mental Disorders of Older People with Down Syndrome and Others with Intellectual Disabilities) and the criteria published by the DSMIG-USA (Down-Syndrome Medical Interest Group USA).

RESULTS

After ruling out somatic or other psychiatric causes, the application of the DSMIG-USA criteria resulted in diagnosing at least a probable unexplained regression in all three patients.

DISCUSSION

The thorough diagnostic investigation of unexplained acute regression in young adults with Down syndrome allows for quick initiation of therapeutic and supportive measures. Using the DMSIG-USA criteria facilitates the assessment of the underlying diffuse and heterogenous pathology.

A Systematic Review of Unexplained Early Regression in Adolescents and Adults with Down Syndrome

A proportion of young people with Down syndrome (DS) experience unexplained regression that severely impacts on their daily lives. While this condition has been recognised by clinicians, there is a limited understanding of causation and an inconsistent approach to diagnosis and treatment. Varied symptomology and little knowledge of the cause of this regression have impacted on clinician's ability to prevent or manage this condition. The purpose of this review was to examine the current evidence surrounding unexplained regression in adolescents and young adults, and to establish patterns that may be of use to clinicians, as well as raising awareness of this condition. Four areas were specifically reviewed, (1) terminology used to refer to this condition, (2) the symptoms reported, (3) potential trigger events and, (4) treatments and prognosis. A variety of terminology is used for this condition, which has constrained past attempts to identify patterns. An extensive number of symptoms were reported, however sleep impairment, loss of language and distinct changes in personality and behaviour, such as disinterest and withdrawal, were among the most frequently seen. Life events that were tentatively associated with the onset of a regressive period included a significant change in environmental circumstances or a transition, such as moving home or leaving school. Prognosis for this condition is relatively positive with the majority of individuals making at least a partial recovery. However, few patients were found to make a full recovery to their previous level of functioning and serious adverse effects could persist in those who have made a partial recovery. This is an under-researched condition with significant impacts on people with DS and their families. There are no established treatments for this condition and there is relatively little recognition in the research community. Further studies that focus on the prevention and treatment of this condition with controlled treatment trials are needed.

Acute Regression in Down Syndrome

BACKGROUND

Acute regression has been reported in some individuals with Down syndrome (DS), typically occurring between the teenage years and mid to late 20s. Characterized by sudden, and often unexplained, reductions in language skills, functional living skills and reduced psychomotor activity, some individuals have been incorrectly diagnosed with Alzheimer's disease (AD).

METHODS

This paper compares five individuals with DS who previously experienced acute regression with a matched group of 15 unaffected individuals with DS using a set of AD biomarkers.

RESULTS

While the sample was too small to conduct statistical analyses, findings suggest there are possible meaningful differences between the groups on proteomics biomarkers (e.g., NfL, total tau). Hippocampal, caudate and putamen volumes were slightly larger in the regression group, the opposite of what was hypothesized. A slightly lower amyloid load was found on the PET scans for the regression group, but no differences were noted on tau PET.

CONCLUSIONS

Some proteomics biomarker findings suggest that individuals with DS who experience acute regression may be at increased risk for AD at an earlier age in comparison to unaffected adults with DS. However, due to the age of the group (mean 38 years), it may be too early to observe meaningful group differences on image-based biomarkers.

Opportunities, barriers, and recommendations in down syndrome research

BACKGROUND

Recent advances in medical care have increased life expectancy and improved the quality of life for people with Down syndrome (DS). These advances are the result of both pre-clinical and clinical research but much about DS is still poorly understood. In 2020, the NIH announced their plan to update their DS research plan and requested input from the scientific and advocacy community.

OBJECTIVE

The National Down Syndrome Society (NDSS) and the LuMind IDSC Foundation worked together with scientific and medical experts to develop recommendations for the NIH research plan.

METHODS

NDSS and LuMind IDSC assembled over 50 experts across multiple disciplines and organized them in eleven working groups focused on specific issues for people with DS.

RESULTS

This review article summarizes the research gaps and recommendations that have the potential to improve the health and quality of life for people with DS within the next decade.

CONCLUSIONS

This review highlights many of the scientific gaps that exist in DS research. Based on these gaps, a multidisciplinary group of DS experts has made recommendations to advance DS research. This paper may also aid policymakers and the DS community to build a comprehensive national DS research strategy.

Case Report: Improvement Following Immunotherapy in an Individual With Seronegative Down Syndrome Disintegrative Disorder

Down syndrome disintegrative disorder (DSDD) is a condition of unknown etiology characterized by acute cognitive decline, catatonia, insomnia, and autistic features in individuals with Down syndrome. A prior report of four patients with DSDD suggested a potential autoimmune etiology based on the presence of autoantibodies and on successful treatment with immunotherapy that included intravenous immunoglobulin (IVIG). Herein, we present the case of an 8-year old girl who developed acute cognitive decline to a dementia-like state, insomnia, catatonia, and autistic features. In contrast to the four patients with DSDD above, she had no evidence of autoimmunity and presented at a younger age. Given the gravity of her acute deterioration and the exclusion of other etiologies, she was treated with immunotherapy presumptively. She responded with near complete resolution of symptoms, but demonstrated a pattern of mild decline as she approached each monthly dosing of IVIG and steroids, reversed by treatment. Mycophenolate mofetil (MMF) was therefore added, with stability throughout the month and the ability to taper off IVIG. After stopping IVIG, she had a mild recurrence of symptoms that again resolved with repeat IVIG followed by tapering off. Outcome was assessed at 2.5 years after presentation, at which time she was back to her premorbid condition, except for persistent tics off immunotherapy. This case supports the contention that patients with a rapid onset of severe symptoms consistent with DSDD, who have a thorough evaluation with the exclusion of other etiologies, may warrant a trial of immunotherapy with steroids, IVIG and/or other agents like MMF even in the absence of evidence of autoimmunity on standard evaluation.

[Cognition in Down's Syndrome: Development across the Life Span and Neuropsychological Assessment in Adults]

Das Down-Syndrom ist die häufigste genetische Ursache einer Intelligenzminderung. Da Menschen mit einem Down-Syndrom ein erhöhtes Risiko aufweisen, an einer Alzheimer-Demenz zu erkranken, ist eine umfassende Untersuchung der kognitiven Funktionen indiziert, sowohl im jungen Erwachsenenalter (zur Erhebung des kognitiven Ausgangsniveaus) als auch im Verlauf zur Demenzdiagnostik. Das weite Spektrum an kognitiver Leistungsfähigkeit bei Menschen mit einem Down-Syndrom stellt eine diagnostische Herausforderung dar. Wir möchten daher einen Überblick geben (1) über die kognitive Entwicklung über die Lebensspanne, (2) über verschiedene mögliche Ursachen kognitiver Veränderungen bei erwachsenen Menschen mit einem Down-Syndrom und (3) über neuropsychologische Diagnostik und entsprechende Verfahren für den Erwachsenenbereich. Schließlich geben wir, auf der Grundlage unserer Erfahrungen, (4) allgemeine Empfehlungen zur Untersuchung und Befundinterpretation bei Menschen mit Intelligenzminderung.

Neurologic complications of Down syndrome: a systematic review

Down syndrome (DS) is one of the most well-recognized genetic disorders. Persons with DS are known to have a variety of co-morbid medical problems, affecting nearly all organ systems. Improved healthcare interventions and research have allowed for increased life span of persons with DS, although disorders of the neurologic system remain underexplored. The purpose of this systematic review is to provide clinically pertinent information on the neurological phenotypes of frequently occurring or clinically relevant conditions. A retrospective review of MEDLINE, Scopus, and Pubmed were used to identify sources among seventeen, clinically relevant, search categories. MeSH terms all contained the phrase "Down Syndrome" in conjunction with the topic of interest. 'Frequently-occurring' was defined as prevalent in more than 10% of persons with DS across their lifespan, whereas 'clinically-relevant' was defined as a disease condition where early diagnosis or intervention can augment the disease course. In total, 4896 sources were identified with 159 sources meeting criteria for inclusion. Seventeen clinical conditions were grouped under the following subjects: hypotonia, intellectual and learning disability, cervical instability, autism spectrum disorder, epilepsy, cerebrovascular disease, Alzheimer's disease and neuropsychiatric disease. The results of this review provide a blueprint for the clinical neurologist taking care of persons with DS across the age spectrum and indicate that there are many underrecognized and misdiagnosed co-occurring conditions in DS, highlighting the need for further research.

Systematic Review of Recent Pediatric Down Syndrome Neuropsychology Literature: Considerations for Regression Assessment and Monitoring

OBJECTIVES

To conduct a systematic review of recent pediatric Down syndrome (DS) neuropsychology research that may be useful to clinicians and researchers examining regression in this population.

METHODS

We reviewed original peer-reviewed articles published between 2013 and 2018 studying neuropsychological profiles in DS.

RESULTS

Thirty-one articles (of 1231 included in the original search) passed all inclusion criteria, were evaluated for bias, and were included in the analysis.

CONCLUSION

Findings argued against a single "DS profile" and revealed multiple within-group differences as well as expected and unexpected differences relative to typically developing children and children with other intellectual and developmental disabilities. Areas identified as most germane to regression monitoring included working memory, inhibition, letter and word identification, navigational route learning, motor skills (when strong at baseline), single word receptive/expressive vocabulary, and adaptive function.

Psychiatric illness and regression in individuals with Phelan-McDermid syndrome

BACKGROUND

Phelan-McDermid syndrome (PMS) is a genetic condition characterized by intellectual disability, speech and language deficits, hypotonia, autism spectrum disorder, and epilepsy. PMS is caused by 22q13.33 deletions or mutations affecting SHANK3, which codes for a critical scaffolding protein in excitatory synapses. SHANK3 variants are also known to be associated with an increased risk for regression, as well as for psychiatric disorders, including bipolar disorder and catatonia. This study aimed to further describe these phenomena in PMS and to explore any relationship between psychiatric illness and regression after early childhood.

METHODS

Thirty-eight people with PMS were recruited to this study through the Phelan-McDermid Syndrome Foundation based on caregiver report of distinct development of psychiatric symptoms. Caregivers completed a clinician-administered semi-structured interview focused on eliciting psychiatric symptomatology. Data from the PMS International Registry were used to confirm genetic diagnoses of participants and to provide a larger sample for comparison.

RESULTS

The mean age of the 38 participants was 24.7 years (range = 13 to 50; SD = 10.06). Females (31 of 38 cases; 82%) and sequence variants (15 of 38 cases; 39%) were over-represented in this sample, compared to base rates in the PMS International Registry. Onset of psychiatric symptoms occurred at a mean age of 15.4 years (range = 7 to 32), with presentations marked by prominent disturbances of mood. Enduring substantial loss of functional skills after onset of psychiatric changes was seen in 25 cases (66%). Symptomst indicative of catatonia occurred in 20 cases (53%). Triggers included infections, changes in hormonal status, and stressful life events.

CONCLUSIONS

This study confirms that individuals with PMS are at risk of developing severe neuropsychiatric illness in adolescence or early adulthood, including bipolar disorder, catatonia, and lasting regression of skills. These findings should increase the awareness of these phenotypes and lead to earlier diagnosis and the implementation of appropriate interventions. Our findings also highlight the importance of genetic testing in the work-up of individuals with intellectual disability and acute psychiatric illness or regression. Future research is needed to clarify the prevalence and nature of psychiatric disorders and regression among larger unbiased samples of individuals with PMS.

Unexplained regression in Down syndrome: 35 cases from an international Down syndrome database

PURPOSE

An entity of regression in Down syndrome (DS) exists that affects adolescents and young adults and differs from autism spectrum disorder and Alzheimer disease.

METHODS

Since 2017, an international consortium of DS clinics assembled a database of patients with unexplained regression and age- and sex-matched controls. Standardized data on clinical symptoms and tiered medical evaluations were collected. Elements of the proposed definition of unexplained regression in DS were analyzed by paired comparisons between regression cases and matched controls.

RESULTS

We identified 35 patients with DS and unexplained regression, with a mean age at regression of 17.5 years. Diagnostic features differed substantially between regression cases and matched controls (p < 0.001 for all but externalizing behaviors). Patients with regression had four times as many mental health concerns (p < 0.001), six times as many stressors (p < 0.001), and seven times as many depressive symptoms (p < 0.001). Tiered medical evaluation most often identified abnormalities in vitamin D 25-OH levels, polysomnograms, thyroid peroxidase antibodies, and celiac screens. Analysis of the subset of patients with nondiagnostic medical evaluations reinforced the proposed definition.

CONCLUSIONS

Our case-control evidence supports a proposed definition of unexplained regression in Down syndrome. Establishing this clinical definition supports future research and investigation of an underlying mechanism.

Immunotherapy in selected patients with Down syndrome disintegrative disorder

Down syndrome disintegrative disorder (DSDD) is an increasingly identified condition characterized by cognitive decline, autistic characteristics, insomnia, catatonia, and psychosis in adolescents and young adults with Down syndrome. Previously we reported a higher rate of autoimmune thyroid disease in these patients compared with unaffected individuals with Down syndrome. We therefore hypothesized DSDD may in some cases be immune-mediated. Here we report four cases of DSDD treated with immunotherapy. Families were interviewed retrospectively for symptoms of cognitive decline, autism, catatonia, psychosis, and insomnia before and after treatment, using established scales where possible. Medical records were reviewed for evaluations and treatment. All four patients received intravenous immunoglobulin with or without additional immunotherapy. Significant improvements were seen in catatonia, insomnia, autistic features, cognition, and psychosis. In this small case series of patients with autoimmunity, core symptoms of DSDD improved significantly after immunotherapy. This supports the hypothesis that, in some patients, DSDD is immune-mediated. Immunotherapy should be considered in the treatment of DSDD, particularly in patients with a history of autoimmunity. WHAT THIS PAPER ADDS: Immunotherapy may improve symptoms of catatonia, insomnia, autism severity, cognitive decline, and psychosis in Down syndrome disintegrative disorder.

Childhood disintegrative disorder and autism spectrum disorder: a systematic review

AIM

In an attempt to clarify the debate surrounding the diagnostic validity of childhood disintegrative disorder (CDD), we systematically reviewed its characteristics and compared it with autism spectrum disorder (ASD).

METHOD

Four databases were searched (PubMed, PsycINFO, Embase, and Web of Science). Included articles had participants with CDD, as defined by symptoms present in the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision and the International Classification of Diseases, 10th Revision. Comparison groups were those with ASD and ASD with regression. Case studies were excluded.

RESULTS

Twenty articles, comprising 96 participants with CDD (80 males, 16 females), were included. Most studies were cross-sectional. The prevalence of CDD was 1.1 to 9.2 per 100 000, with a mean age at regression of 3 years 2 months (SD 1y 1mo), with a range of 2 years to 7 years. In addition to core CDD symptoms, most had intellectual impairment, anxiety, challenging behaviours, and regressed in toileting skills. Participants with CDD and ASD shared core diagnostic and extra-diagnostic features. However, participants with CDD seemed to have more severe symptoms and a different symptom profile, including apparently typical development before regression, faster regression, more affective symptoms, and more global developmental deficit. Possible genetic and autoimmune neurobiological mechanisms were identified.

INTERPRETATION

There is limited high-quality evidence describing the aetiology and outcomes of CDD. However, given the qualitative and prognostic differences between ASD and CDD, we recommend that future diagnostic criteria should distinguish late-onset regression.

Dementia in Down syndrome: unique insights for Alzheimer disease research

Virtually all adults with Down syndrome (DS) show the neuropathological changes of Alzheimer disease (AD) by the age of 40 years. This association is partially due to overexpression of amyloid precursor protein, encoded by APP, as a result of the location of this gene on chromosome 21. Amyloid-β accumulates in the brain across the lifespan of people with DS, which provides a unique opportunity to understand the temporal progression of AD and the epigenetic factors that contribute to the age of dementia onset. This age dependency in the development of AD in DS can inform research into the presentation of AD in the general population, in whom a longitudinal perspective of the disease is not often available. Comparison of the risk profiles, biomarker profiles and genetic profiles of adults with DS with those of individuals with AD in the general population can help to determine common and distinct pathways as well as mechanisms underlying increased risk of dementia. This Review evaluates the similarities and differences between the pathological cascades and genetics underpinning DS and AD with the aim of providing a platform for common exploration of these disorders.

Down syndrome

Down syndrome (DS; Trisomy 21) is the most common chromosomal disorder in humans. It has numerous associated neurologic phenotypes including intellectual disability, sleep apnea, seizures, behavioral problems, and dementia. With improved access to medical care, people with DS are living longer than ever before. As more individuals with DS reach old age, the necessity for further life span research is essential and cannot be overstated. There is currently a scarcity of information on common medical conditions encountered as individuals with DS progress into adulthood and old age. Conflicting information and uncertainty about the relative risk of dementia for adults with DS is a source of distress for the DS community that creates a major obstacle to proper evaluation and treatment. In this chapter, we discuss the salient neurologic phenotypes of DS, including Alzheimer's disease (AD), and current understanding of their biologic bases and management.

Pharmacotherapy of Down syndrome

Introduction: Comorbid psychiatric disorders are common in Down syndrome (DS). Evidence for pharmacotherapy of psychiatric co-morbidity in DS is limited. Areas covered: This article reviews the literature on the pharmacotherapy of psychiatric conditions co-occurring with DS, including major depressive disorder (MDD), bipolar disorder, anxiety disorders, obsessive-compulsive disorder (OCD), attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), psychosis, and catatonia. A section on the phenomenon of regression is included. Expert opinion: For MDD, we typically begin with selective serotonin reuptake inhibitors (SSRIs). For bipolar disorder, we often use carbamazepine. For psychotic symptoms, we begin with risperidone or aripiprazole. We use buspirone to treat anxiety. For obsessional slowness/OCD, we begin with an SSRI. For stereotypical repetitive behavior, we tend to use buspirone. For ADHD, we begin with guanfacine. For irritability of comorbid ASD, we use risperidone or aripiprazole. For dementia in DS, we refer to a neurologist for medical work-up and medication management. We treat catatonia-like 'regression' with lorazepam. If ineffective, we use memantine or clozapine. Electroconvulsive therapy is considered if pharmacotherapy is ineffective. We treat 'regression' with symptoms of MDD ± psychosis, with an antidepressant and an antipsychotic if needed. Randomized controlled trials of medications for comorbid psychiatric disorders in DS are warranted.

Psychological Support for Young Adults with Down Syndrome: Dohsa-Hou Program for Maladaptive Behaviors and Internalizing Problems

Psychological and psychiatric dysfunction is a major problem in a substantial proportion of young adults with Down syndrome. Some patients develop psychiatric issues, such as depressive, obsessive-compulsive, or psychotic-like disorders, in their late adolescence or young adulthood. Furthermore, these individuals may experience moderate to severe emotional and psychological distress. Development of a psychosocial treatment to address these issues is needed in addition to psychotropic medication. The current study reports two cases of young adults with Down syndrome, who presented psychiatric symptoms and marked disruption in their daily lives. These individuals participated in a Dohsa-hou treatment program. Following treatment, adaptive levels, maladaptive behaviors, and internalizing problems were evaluated by the Vineland Adaptive Behavior Scales-II. Participants showed improvement in maladaptive behaviors and internalizing problems; however, improvement in these areas may be influenced by baseline severity of the problems. This case report suggests that Dohsa-hou could be an effective therapeutic approach for maladaptive and internalizing problems in adults with Down syndrome.

Acute Regression in Young People with Down Syndrome

Abstract: Adolescents and young adults with Down syndrome (DS) can present a rapid regression with loss of independence and daily skills. Causes of regression are unknown and treatment is most of the time symptomatic. We did a retrospective cohort study of regression cases: patients were born between 1959 and 2000, and were followed from 1984 to now. We found 30 DS patients aged 11 to 30 years old with history of regression. Regression occurred regardless of the cognitive level (severe, moderate, or mild intellectual disability (ID)). Patients presented psychiatric symptoms (catatonia, depression, delusions, stereotypies, etc.), partial or total loss of independence in activities of daily living (dressing, toilet, meals, and continence), language impairment (silence, whispered voice, etc.), and loss of academic skills. All patients experienced severe emotional stress prior to regression, which may be considered the trigger. Partial or total recovery was observed for about 50% of them. In our cohort, girls were more frequently affected than boys (64%). Neurobiological hypotheses are discussed as well as preventative and therapeutic approaches.

Outcome Measures for Clinical Trials in Down Syndrome

Increasingly individuals with intellectual and developmental disabilities, including Down syndrome, are being targeted for clinical trials. However, a challenge exists in effectively evaluating the outcomes of these new pharmacological interventions. Few empirically evaluated, psychometrically sound outcome measures appropriate for use in clinical trials with individuals with Down syndrome have been identified. To address this challenge, the National Institutes of Health (NIH) assembled leading clinicians and scientists to review existing measures and identify those that currently are appropriate for trials; those that may be appropriate after expansion of age range addition of easier items, and/or downward extension of psychometric norms; and areas where new measures need to be developed. This article focuses on measures in the areas of cognition and behavior.

Cognitive decline and dementia in Down syndrome

PURPOSE OF REVIEW

Alzheimer's disease is most likely universal in older individuals with Down syndrome, due to having three copies of the amyloid precursor protein gene, resulting in amyloid-beta plaque deposition. Down syndrome is an important population in which to consider clinical trials of treatments to prevent or delay the development of dementia. However, assessment of subtler cognitive changes is challenging due to the presence of intellectual disability.

RECENT FINDINGS

Recent research confirmed that older adults with Down syndrome often present with cognitive decline: more than 80% may experience dementia by age 65 years. Efforts have been made to improve and validate neuropsychological assessment and to describe the relationship with comorbidities such as epilepsy and haemorrhagic stroke. There have also been advances in biomarkers such as neuroimaging using amyloid PET.

SUMMARY

Clinical trials of treatments, particularly in the presymptomatic phase of Alzheimer's disease, are important to consider in individuals with Down syndrome given their high dementia burden, and may also serve as proof of concept for other forms of Alzheimer's disease. However, further work is required to improve outcome measures and better understand the biomarkers of progression of disorder and their relationship with symptom development during the presymptomatic period.

Rapid clinical deterioration in an individual with Down syndrome

A small percentage of adolescents and young adults with Down syndrome experience a rapid and unexplained deterioration in cognitive, adaptive, and behavioral functioning. Currently, there is no standardized work-up available to evaluate these patients or treat them. Their decline typically involves intellectual deterioration, a loss of skills of daily living, and prominent behavioral changes. Certain cases follow significant life events such as completion of secondary school with friends who proceed on to college or employment beyond the individual with DS. Others develop this condition seemingly unprovoked. Increased attention in the medical community to clinical deterioration in adolescents and young adults with Down syndrome could provide a framework for improved diagnosis, evaluation, and treatment. This report presents a young adult male with Down syndrome who experienced severe and unexplained clinical deterioration, highlighting specific challenges in the systematic evaluation and treatment of these patients. © 2016 Wiley Periodicals, Inc.