Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 4 complete abstracts (810 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
A chromosome disorder associated either with an extra chromosome 21 or an effective trisomy for chromosome 21. Clinical manifestations include hypotonia, short stature, brachycephaly, upslanting palpebral fissures, epicanthus, Brushfield spots on the iris, protruding tongue, small ears, short, broad hands, fifth finger clinodactyly, single transverse palmar crease, and moderate to severe intellectual disability. Cardiac and gastrointestinal malformations, a marked increase in the incidence of leukemia, and the early onset of alzheimer disease are also associated with this condition. Pathologic features include the development of neurofibrillary tangles in neurons and the deposition of amyloid beta-protein, similar to the pathology of alzheimer disease. (Menkes, Textbook of Child Neurology, 5th ed, p213)
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Syndrome, Down; Down's Syndrome; Downs Syndrome; Syndrome, Down's; Mongolism; Trisomy 21; Trisomy G; 47,XX,+21.
Where it fits in the MeSH classification
- Broader topics
- Intellectual Disability; Abnormalities, Multiple; Chromosome Disorders
Related concepts
- Chromosomes
- Trisomy
- Hypotonia
- Brachycephaly
- Intellectual Disability
- Leukemia
- Alzheimer Disease
- Neurofibrillary Tangles
- Amyloid Beta-Protein
Research landscape
PubMed indexes 28,168 records tagged with the MeSH heading “Down Syndrome” (counts retrieved 2026-10-29). 3,868 of them (13.7%) were published from 2020 onward, and the busiest period so far is through 1999 with 12,601 records.
Reviews account for 2,840 records (10.1%) and meta-analyses for 188. Randomized controlled trials number 274 (1.0%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.
Show the data
| Period | Records |
|---|---|
| through 1999 | 12,601 |
| 2000-2009 | 5,469 |
| 2010-2019 | 6,230 |
| 2020 onward | 3,868 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 2,840 | 10.1% |
| Meta-analyses | 188 | 0.7% |
| Randomized controlled trials | 274 | 1.0% |
Method: PubMed query "Down Syndrome"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-29.
Reading the evidence in rare and inherited diseases
Rare conditions are difficult to study: few patients means small studies, case reports and registries are common, and randomized trials are the exception. Small samples limit precision and can exaggerate effects, and cases reported in the literature may be the most severe or unusual. Evidence from many small studies is best read together. Check how patients were identified, how many were included and how long they were followed.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| The Alzheimer's Biomarker Consortium-Down Syndrome (ABC-DS): A 10-year report | 2025 | Research article Design not recorded in structured metadata | 20 | cc by PMID 40371686 · DOI · PMC12079517 |
| Resistance and resilience to Alzheimer's disease in Down syndrome | 2025 | Review article Design not recorded in structured metadata | 14 | cc by PMID 40289889 · DOI · PMC12035553 |
| Down syndrome with Alzheimer's disease brains have increased iron and associated lipid peroxidation consistent with ferroptosis | 2025 | Research article Design not recorded in structured metadata | 10 | cc by PMID 40536124 · DOI · PMC12177674 |
| Impaired BDNF-TrkB trafficking and signalling in Down syndrome basal forebrain neurons | 2026 | Research article Design not recorded in structured metadata | 5 | cc by PMID 41667435 · DOI · PMC12921309 |
The Alzheimer's Biomarker Consortium-Down Syndrome (ABC-DS): A 10-year report [1]
Abstract reading summary — source excerpts
- Opening excerpt
- IntroductionVirtually all adults with Down syndrome (DS) will accumulate the neuropathologies associated with Alzheimer's disease (AD) by age 40, with the majority having a clinical dementia diagnosis by their middle 50s.
- Closing excerpt
- It is positioned to continue to make substantial contributions to the DS field.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (224 words)
IntroductionVirtually all adults with Down syndrome (DS) will accumulate the neuropathologies associated with Alzheimer's disease (AD) by age 40, with the majority having a clinical dementia diagnosis by their middle 50s.MethodsThis paper complements a 2020 publication describing the Alzheimer's Biomarker Consortium-Down Syndrome (ABC-DS) methodology by highlighting protocol changes since initial funding in 2015. It describes available clinical, neuropsychological, neuroimaging, and biofluid data and bio-specimen repository. Ten years of accomplishments are summarized.ResultsOver 500 adults with DS and 59 sibling controls have been enrolled since 2015 with nearly 800 follow-up visits. More than 900 magnetic resonance imaging (MRI), 800 amyloid positron emission tomography (PET), and 600 tau PET scans have been conducted; multiple omics data have been generated using over 1100 blood and 100 cerebrospinal fluid (CSF) samples.DiscussionABC-DS is the largest U.S.-based, multi-site (including the United Kingdom and Puerto Rico), longitudinal biomarker initiative to target adults with DS at risk for AD.HighlightsThe Alzheimer's Biomarker Consortium-Down Syndrome (ABC-DS) is entering its 10th year. Over 500 adults with Down syndrome (DS) and 59 sibling controls have been enrolled. More than 900 magnetic resonance imaging (MRI), 800 amyloid positron emission tomography (PET), and 600 tau PET scans have been conducted. Multiple omics data have been generated using over 1100 blood and 100 cerebrospinal fluid (CSF) samples. It is positioned to continue to make substantial contributions to the DS field.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40371686 · DOI · PMC12079517
Resistance and resilience to Alzheimer's disease in Down syndrome [2]
Abstract reading summary — source excerpts
- Opening excerpt
- Due to the high prevalence of Alzheimer's disease (AD) in adults with Down syndrome (DS), trisomy 21 is now considered a genetic form of AD (DSAD).
- Closing excerpt
- Future research will require longitudinal and experimental designs, life course approaches, and large cohort studies.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (211 words)
Due to the high prevalence of Alzheimer's disease (AD) in adults with Down syndrome (DS), trisomy 21 is now considered a genetic form of AD (DSAD). A better understanding of factors that can prevent or delay AD is vital to improve outcomes for adults with DS. In this narrative review, we apply AD and cognitive aging research frameworks to study resistance and resilience in DSAD. Given the variability in the timing of pathology and symptoms, we discuss the evidence supporting the role of genetic, biological, socio-behavioral, lifestyle, and environmental factors in resistance and resilience to DSAD. We also consider how co-occurring health conditions in DS may influence resistance and resilience, and how methods from AD research can be applied to DSAD. Ultimately, this framework aims to guide future research and translate findings into clinical interventions to improve outcomes in DSAD. Highlights Definitions of resistance and resilience in the genetic form of Alzheimer's disease (DSAD) are proposed for guiding the field. Variability in the timing of AD pathology and symptoms suggests the potential for resistance and resilience mechanisms in DSAD. Genetic, biological, socio-behavioral, lifestyle, and environmental factors have the potential to build resistance or resilience in DSAD. Future research will require longitudinal and experimental designs, life course approaches, and large cohort studies.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40289889 · DOI · PMC12035553
Down syndrome with Alzheimer's disease brains have increased iron and associated lipid peroxidation consistent with ferroptosis [3]
Abstract reading summary — source excerpts
- Opening excerpt
- IntroductionCerebral microbleeds (MBs) are associated with sporadic Alzheimer's disease (AD) and Down syndrome with AD (DSAD).
- Closing excerpt
- Partial and mosaic trisomy lowers the amyloid and iron burden.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (174 words)
IntroductionCerebral microbleeds (MBs) are associated with sporadic Alzheimer's disease (AD) and Down syndrome with AD (DSAD). Higher MB iron may cause iron-mediated lipid peroxidation. We hypothesize that amyloid deposition is linked to MB iron and that amyloid precursor protein (APP) triplication increases iron load and lipid peroxidation.MethodsPrefrontal cortex and cerebellum of cognitively normal control (CTL), AD, and DSAD ApoE3,3 carriers were examined for proteins that mediated iron metabolism, antioxidant response, and amyloid processing in lipid rafts.ResultsIron was twofold higher in DSAD than in CTL and AD. Iron storage proteins and lipid peroxidation were increased in the prefrontal cortex. The glutathione synthesis protein GCLM was decreased by 50% in both AD and DSAD. Activity of lipid raft GPx4, responsible for membrane repair, was decreased by at least 30% in AD and DSAD.DiscussionDSAD shows greater lipid peroxidation than AD, consistent with greater MBs and iron load.HighlightsDSAD has increased ferroptotic-related changes compared to sporadic AD. Lipid rafts that process APP have a loss of protective antioxidant enzymes. Partial and mosaic trisomy lowers the amyloid and iron burden.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40536124 · DOI · PMC12177674
Impaired BDNF-TrkB trafficking and signalling in Down syndrome basal forebrain neurons [4]
Abstract reading summary — source excerpts
- Opening excerpt
- Brain derived neurotrophic factor (BDNF) and its receptor tropomyosin-related kinase B (TrkB) play crucial roles in neuronal development, synaptic transmission, and neuroplasticity.
- Closing excerpt
- Our findings establish a link between Rab5 hyperactivation, endosomal dysfunction, and impaired ERK1/2 signalling, highlighting the interplay between trafficking and neurotrophic signalling, and underscore the importance of targeting endolysosomal and signalling pathways to mitigate neuronal dysfunction in AD-DS.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (201 words)
Brain derived neurotrophic factor (BDNF) and its receptor tropomyosin-related kinase B (TrkB) play crucial roles in neuronal development, synaptic transmission, and neuroplasticity. Deficits in BDNF/TrkB signalling and trafficking have been identified in several neurodegenerative diseases, including Alzheimer's disease (AD). Individuals with Down syndrome (DS) are at an increased risk of developing AD compared to the general population. Basal forebrain neurons (BFNs) are among the first to degenerate in AD and DS, but the mechanisms underlying their vulnerability remain unclear. Using BFNs derived from the Dp1Tyb mouse model of DS, we investigated neurotrophic signalling and trafficking deficits in AD-DS. We found enlarged early endosomes and elevated levels of active Rab5, a GTPase critical for early endosome formation, in Dp1Tyb BFNs. These abnormalities were associated with impaired transport of internalised TrkB from axon terminals to the soma. Using microfluidic devices, we demonstrated that axonal BDNF stimulation enhanced signalling endosome dynamics in wild-type but not Dp1Tyb BFNs, which is likely due to impaired axonal ERK1/2 signalling. Our findings establish a link between Rab5 hyperactivation, endosomal dysfunction, and impaired ERK1/2 signalling, highlighting the interplay between trafficking and neurotrophic signalling, and underscore the importance of targeting endolysosomal and signalling pathways to mitigate neuronal dysfunction in AD-DS.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41667435 · DOI · PMC12921309
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article Analysis of cell-free DNA in maternal blood in screening for aneuploidies: updated meta-analysis [5]
- Research article Analysis of cell-free DNA in maternal blood in screening for fetal aneuploidies: updated meta-analysis [6]
- Research article Alzheimer's disease associated with Down syndrome: a genetic form of dementia [7]
- Research article Cystathionine-β-Synthase: Molecular Regulation and Pharmacological Inhibition [8]
- Research article Association of Alzheimer Disease With Life Expectancy in People With Down Syndrome [9]
- Research article Noninvasive prenatal screening (NIPS) for fetal chromosome abnormalities in a general-risk population: An evidence-based clinical guideline of the American College of Medical Genetics and Genomics (ACMG) [10]
References
- Handen BL, Mapstone M, Hartley S, Andrews H, Christian B, Lee JH, et al.. The Alzheimer's Biomarker Consortium-Down Syndrome (ABC-DS): A 10-year report. . 2025. PMID 40371686 · DOI · PMC12079517
- Boyle R, Koops EA, Ances B, Andrews EJ, Arenaza-Urquijo EM, Bejanin A, et al.. Resistance and resilience to Alzheimer's disease in Down syndrome. . 2025. PMID 40289889 · DOI · PMC12035553
- Thorwald MA, Godoy-Lugo JA, Kerstiens E, Garcia G, Kim M, Shemtov SJ, et al.. Down syndrome with Alzheimer's disease brains have increased iron and associated lipid peroxidation consistent with ferroptosis. . 2025. PMID 40536124 · DOI · PMC12177674
- Blackburn E, Birsa N, Lopes AT, Fisher EMC, Lazo OM, Schiavo G. Impaired BDNF-TrkB trafficking and signalling in Down syndrome basal forebrain neurons. . 2026. PMID 41667435 · DOI · PMC12921309
- Gil MM, Accurti V, Santacruz B, Plana MN, Nicolaides KH. Analysis of cell-free DNA in maternal blood in screening for aneuploidies: updated meta-analysis. Ultrasound Obstet Gynecol. 2017. PMID 28397325 · DOI
- Gil MM, Quezada MS, Revello R, Akolekar R, Nicolaides KH. Analysis of cell-free DNA in maternal blood in screening for fetal aneuploidies: updated meta-analysis. Ultrasound Obstet Gynecol. 2015. PMID 25639627 · DOI
- Fortea J, Zaman SH, Hartley S, Rafii MS, Head E, Carmona-Iragui M. Alzheimer's disease associated with Down syndrome: a genetic form of dementia. Lancet Neurol. 2021. PMID 34687637 · DOI · PMC9387748
- Zuhra K, Augsburger F, Majtan T, Szabo C. Cystathionine-β-Synthase: Molecular Regulation and Pharmacological Inhibition. Biomolecules. 2020. PMID 32365821 · DOI · PMC7277093
- Iulita MF, Garzón Chavez D, Klitgaard Christensen M, Valle Tamayo N, Plana-Ripoll O, Rasmussen SA, et al.. Association of Alzheimer Disease With Life Expectancy in People With Down Syndrome. JAMA Netw Open. 2022. PMID 35604690 · DOI · PMC9127560
- Dungan JS, Klugman S, Darilek S, Malinowski J, Akkari YMN, Monaghan KG, et al.. Noninvasive prenatal screening (NIPS) for fetal chromosome abnormalities in a general-risk population: An evidence-based clinical guideline of the American College of Medical Genetics and Genomics (ACMG). Genet Med. 2023. PMID 36524989 · DOI
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-29.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.