Trisomy 21 (T21) causes Down syndrome (DS), but the mechanisms by which T21 produces the different disease spectrum observed in people with DS are unknown. We recently identified an activated interferon response associated with T21 in human cells of different origins, consistent with overexpression of the four interferon receptors encoded on chromosome 21, and proposed that DS could be understood partially as an interferonopathy. However, the impact of T21 on systemic signaling cascades in living individuals with DS is undefined. To address this knowledge gap, we employed proteomics approaches to analyze blood samples from 263 individuals, 165 of them with DS, leading to the identification of dozens of proteins that are consistently deregulated by T21. Most prominent among these proteins are numerous factors involved in immune control, the complement cascade, and growth factor signaling. Importantly, people with DS display higher levels of many pro-inflammatory cytokines (e.g. IL-6, MCP-1, IL-22, TNF-α) and pronounced complement consumption, resembling changes seen in type I interferonopathies and other autoinflammatory conditions. Therefore, these results are consistent with the hypothesis that increased interferon signaling caused by T21 leads to chronic immune dysregulation, and justify investigations to define the therapeutic value of immune-modulatory strategies in DS.

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Aspiration is an often unrecognized comorbidity in children with Down syndrome with serious medical consequences. This retrospective chart review of swallow study reports characterizes oral and pharyngeal phase dysphagia and diet modifications on videofluoroscopic swallow studies (VFSS) in a large cohort of children with Down syndrome. A total of 158 pediatric patients (male = 95; female = 63; mean age 2.10 years, SD 3.17 years) received an initial VFSS at a pediatric teaching hospital as part of their medical care. A total of 56.3 % (n = 89) children had pharyngeal phase dysphagia with aspiration and deep laryngeal penetration occurring most frequently. Of the 61 patients who aspirated, 90.2 % (n = 55) did so silently with no cough or overt clinical symptoms. In 76.7 % of cases of pharyngeal phase dysphagia, a functional feeding plan, with use of thickened liquids or change in feeding system to control flow rate and/or bolus size, was able to be established, which allowed children to continue eating by mouth. Thickened liquids (76.7 %, n = 46) were the most effective adaptation, with change in feeding system alone effective in only 8.3 % (n = 5) cases. Oral phase dysphagia was reported in the majority of patients (63.8 %, n = 88/138); however, this was not predictive of pharyngeal phase dysphagia. Age, sex, and reason for referral, including prior clinical symptoms, did not have a statistically significant impact on the presence of dysphagia. This comprehensive review has application to clinical understanding and management of dysphagia in children with Down syndrome.

Children with trisomy 21 and autism have significantly more impaired brain function than children with trisomy 21 without autism. However, the deficits in the core domains of social reciprocity and communication, and the restricted and repetitive interests are not entirely explained by the more severe cognitive impairment. This autism phenotype in children with trisomy 21 which includes an increased risk for seizures may indicate a widespread loss of functional connectivity in the brain.