Contribution of Family History in Co-occurring Down Syndrome and Ehlers-Danlos Syndrome.

Nearly all children with Down syndrome (DS) are born with hypotonia which later improves with age. We present a case of a 32-month-old female with DS who has persistent hypotonia and ligamentous hyperlaxity. She was subsequently diagnosed with Ehlers-Danlos Syndrome-Hypermobility type (EDS-HMT) based on family history, which resulted in the significant global developmental delay compared to age-matched peers with DS. Further clinical investigation is recommended in individuals with DS who appear to have developmental profiles significantly below what would be expected due to typical Trisomy 21 so that additional diagnostic testing and appropriate interventional therapy may be provided. Specifically, timely diagnosis of inherited disorders such as EDS-HMT is important in identifying other family members with the condition.