Diagnosis and differential diagnosis of Asperger syndrome

Asperger syndrome is an uncommon condition, but probably more common than classic autism (the only published population study estimated prevalence at 36 per 10 000 children for Asperger syndrome and 5 per 10 000 for autism (Ehlers & Gillberg, 1993)). Misdiagnosis or delayed diagnosis of this disorder is a serious problem, and the average age at diagnosis is several years later than for autism (Gillberg, 1989). Obviously, this can be traumatic for individuals and families; furthermore, the most effective intervention programmes begin early, and establishing management strategies at an early age can minimise later behavioural problems (Howlin, 1998). In 1944 Hans Asperger described a condition he termed autistic psychopathy, characterised by problems in social integration and non-verbal communication associated with idiosyncratic verbal communication and an egocentric preoccupation with unusual and circumscribed interests. Patients with this condition had difficulties with empathy and intuition and had a tendency to intellectualisation. They were also clumsy (50–90% had motor coordination problems), found it hard to take part in team sports and exhibited behavioural difficulties including aggression and being victims of bullying. Asperger did not provide diagnostic criteria for this condition and it remained obscure until a review article by Lorna Wing in 1981. Wing renewed interest in the condition, which she renamed Asperger syndrome, and described the following difficulties in the first 2 years of life of children with the condition: