NIH, CDC and Autism Speaks are looking into the question of increased prevalence in autism rates for US born Somali Children. (link)
Back in March of 2009, NY Times Donald McNeil reported that the Minnesota Health Department concurred with a concept that Somali children, born in the US, have higher than usual rates of autism as compared to the general US population. Similar findings are acknowledged in Sweden's Somali population.
Genetic differences are proposed as the cause for increased susceptibility to autism, according to a September 2008 piece by Virginia Huges of Sfari.
Autism seems to be thought of as unknown in Somalia, but it is reasonable to point out that even as autism is considered unknown for that region - that doesn't necessarily mean that the characteristics displayed that are thought of as autism here in the US, are not displayed in Somalia; and are not identified with any given label.
The true autism rate in Somalia needs to be investigated further according to Virginia Hughes.
According to Steven Novella in Neurologiablog, November 2008;
...autism is really a collection of diseases, not a specific disease. So we may be seeing a new entity that has clinical overlap in features and symptoms - with recognized forms of autism.
Clinical overlap of features displayed, and the resulting labels chosen are experienced with frequency in the field of neurology.
Since Vitamin D has been given a lot of attention in the news lately...Some hypothesize that higher rates of autism are experienced by US born Somali children due to the lower levels of sunlight and the differences in our US diet. Ancestry has affected the Somali childrens' genetics and therefore the overall difference in environment, in that their ancestry lived by the equator and ate a diet which included fatty fish, is enough to cause a deficiency that is affecting their overall development. (link)