Table 9.4.

Specific areas to assess in the differential diagnosis by syndrome

Genetic syndrome	Relative strengths in the absence of autism	Tools to assess these areas
Down syndrome	Social interest Frequent attempts to communicate Rich emotion sharing Frequent social initiations	•Communication and Symbolic Behavior Scales (Wetherby & Prizant, 2005) •Parent-child play •High affect, stimulating play •Screening for tool for autism in toddlers (STAT; Stone, Coonrod, Turner, & Pozdol, 2004)
Williams syndrome	Emotional contagion Social play Functional imitation Frequency of social initiations Quality of social responses Nature of pragmatic difficulties	•Birthday party from ADOS with surprise present added to play activity •Empathy tasks (see Yirmiya, Sigman, Kasari, & Mundy, 1992) •Children's Communication Checklist (Bishop, Chan, Adams, Hardey, & Weir, 2000) •Imitation activities from the STAT (Stone et al., 2004) or the ADOS (Lord, Rutter, DiLavore, & Risi, 1999)
Angleman syndrome	Soothability by social contact Attempts to interact socially Emotional contagion	•Parent-child play •Sensory-social routines from Early Start Denver Model (Rogers & Dawson, 2010) •High affect, stimulating play
Fragile X syndrome	Receptive language skills Imitation skills Social orienting Sensory reactivity	•Preschool Language Scales (PLS; Zimmerman, Steiner, & Pond, 2002) or Clinical Evaluation of Language Fundamentals (CELF; Semel, Wiig, & Secord, 2000), or another standardized assessment of language that includes both receptive and expressive language and has appropriate norms •Imitation items, either from the STAT or ADOS •Birthday party from the ADOS, with surprise present added to routine •Short Sensory Profile (Mcintosh, Miller, Shyu, & Dunn, 1999)