1. Other forms of mutism. Mutism can be the result of physical or psychological conditions. Medical conditions that result in the loss of the ability to speak is manifold and includes brain disease as well specific injuries to the brain. If a child becomes mute when he/she was previously able to speak, there is a need to make sure that no physical malady has struck. We have seen a 13 year old with epilepsy presenting as mutism. It was the result of a rare form of mutism associated with epilepsy. Sometimes mutism can be the result of a psychological trauma as well. A child seen at the Child Guidance Clinic was mute after he witnessed his father murdering his mother. All these forms of mutism are often pervasive and not in particular situations.

2. Language disorders. Stuttering is common articulation problem and children with this difficulty may choose to minimise their speech for fear of teasing. This, of itself, should not lead to a diagnosis of selective mutism. We are aware that a number of studies have pointed to the fact that selectively mute children often have a number of language related problems and we are trying to study this understudied area.

3. Pervasive Developmental Disorders (PDD). Many children with PDD may be selective in their speech. However, they have far more problematic lives because they may have language disabilities, learning disabilities, socialisation problems as well as odd behaviours. If a child has PDD, he should not be diagnosed as selective mutism as his problem is more than just not speaking in specific situations. There is obviously some overlap in this area. But at this point in time, research is still not sufficient to determine the relationship between selective mutism and the autism spectrum disorders.

4. Not speaking the language of instruction in school. This is by far the most common reason why young children do not speak in school. In Singapore, most children speak their mother tongue at home and when they start school, the transition to English may be difficult for some. This should not be considered selective mutism. In Toronto, many children come from immigrant families where English is not the medium of communication at home. If such children start school and do not speak, it would be important to distinguish the inability of the child to speak the language with the inability to speak in that particular situation.