Little is known about this new mental disorder, thus people are still trying to figure out what the diagnostic criteria for misophonia are. One study  suggests that misophonia is a completely new mental disorder which doesn’t fit in mood disorders, anxiety disorders, personality disorders and so on. This study found the following diagnostic criteria :
According to this study  (small scale, n=42) the age of onset for misophonia is 13 years old (ranging from age 2 to 38). According to these 42 patients the triggering sounds were all produced by human beings (except for their own sounds),. However, animal or other sounds did not cause any problem for these patients. 81% of the patients reported that their triggers were eating-related sounds people make. 61.3% of the patients reported that their triggers were related to breathing or nose sounds. 59.5% of the patients reported being triggered by sounds of a clicking pen or typing on a keyboard .
Study  mentions that the sounds can also be produced by machines (distant airplane or train) or by animals and that this annoyance and irritation with the particular sound probably developed during childhood/adolescence.
If left untreated misophonia negatively affects performance at school, work, family, and social domains. On top of that, avoidance of the particular sound also negatively affect someone’s ability to achieve goals and enjoy social activities .
Although there are no evidence based treatments available at the moment, cognitive behavioural therapy (CBT) and Tinnitus retraining therapy (TRT) have been proposed to be effective treatments . Note: the studies testing both the effectiveness of CBT and TRT in reducing the misophonia symptoms were limited in their group size, which makes it more likely that the treatment effectiveness could be explained by other factors but just therapy.
Eye Movement Desensitization and Reprocessing (EMDR) has been effective in treating misophonia in a pilot study, but these data need to be reproduced to say something meaningful about it, therefore we’ve decided to apply EMDR to people with Misophonia.
Fortunately, currently more researchers are busy trying to find an evidence based misophonia treatment. This page will keep you updated.