The continuing challenge of diagnosing autism spectrum disorder in children with Down syndrome

Traditionally, the association between autism spectrum disorder (ASD) and Down syndrome (DS) was considered uncommon, as the stereotype image of an individual with DS was (and continues to be) a friendly, affectionate and outgoing personality (Ghaziuddin et al. 1992). Identifying children with DS who also meet ICD-10/DSM-IV criteria for ASD (DS-ASD) continues to be a challenge for clinicians and parents. Following 20 years of research in which the prevalence of DS-ASD varied from 1% to 12% (Ghaziuddin et al. 1992; Kent et al. 1999; Capone et al. 2005; Starr et al. 2005; Carter et al. 2007; Hepburn et al. 2008; Molloy et al. 2009; Reilly 2009), DiGuiseppi and colleagues (2010) have used screening tools and standardized diagnostic measures in a population-based cohort of 123 children with DS (mean age: 6.1 years) and reported 18% to have ASD and 7% autism. DiGuiseppi’s study is the most robust to date and, while limitations remain and further research is necessary, we now know more than ever about DS-ASD. Taking DiGuiseppi’s prevalence findings into account, we believe DS-ASD remains under-diagnosed. There are many reasons for this, some of which are discussed below, with quotes from some parents and clinicians who were canvassed in preparation for this editorial. Some quotes sum up the challenges for parents and clinician alike. Opinions differ between professionals about whether, and when, an additional neurodevelopmental diagnosis should be given. Parental opinion on the desirability of the diagnosis is similarly variable – some parents find an ASD diagnosis valuable and others do not. Although there are often many other conditions associated with DS (Roizen & Patterson 2003), some parents report that the ASD behaviours displayed by their child are hardest to cope with, and have the biggest impact: ‘Of [my child’s] three conditions autism is most difficult, then Hirschsprungs then DS (which is by far the easiest to deal with!)’. Parents reported that professionals have a wide-ranging level of understanding about DS-ASD: ‘It is hard on us all. We cope and put on a good front of coping (as you have to) but to be honest we don’t cope. It is hard to explain to other people and professionals what it is really like . . . some professionals identify completely . . . others have little understanding and expect him to act like other DS children’. Some parents faced absolute disbelief from professionals about a possible DS-ASD diagnosis: ‘Everyone I approached thought he either couldn’t, definitely didn’t or shouldn’t have autism’. Other clinicians may be unable to see what benefit an additional diagnosis may bring: ‘[The Consultant said] he didn’t think anything would be gained by having [my child] assessed’. Some parents commented that their child had been diagnosed later than hoped for, delaying an explanation for certain behaviours and impacting on the availability of early intervention and support for ASD-related issues from health, education and social care services, and from their own family. As discussed by Lenhard Child: care, health and development Editorial doi:10.1111/j.1365-2214.2011.01218.x