A natural reaction to diseases in colds, cough etc is psoric; something less or more, like less or more blood pressure etc is sycotic; and things getting to destruction, like cancer etc is syphilitic. Further, miasms are not just present when we have diseases, rather they are a part and parcel of our lifestyle. A natural reaction to something in a nice way is psoric; we saying something less or more to somebody, by keeping in mind his state of mind is sycotic; and any act of destruction, be it carried out in mind is syphilitic.
So these are the three ways of defence we show to the outside stimuli, and we can't eliminate them. Thus, all the foolish talks to eliminate miasms is done by fools only, who in reality don't even know the reality on miasms, and neither have an idea of it.
What is done by right homeopathic medicines by itself is to heal the disposition to show a particular miasm, and thus the problems caused by it. In autism it's less of development, and thus more of sycotic miasm exhibited by the kid, that too in quite a suppressed form in his or her affected energies. The right words rather would be, that energies are suppressed to quite more an extent and in such a way that sycotic miasm is being exhibited in a great way.
One more truth not known to people is that every homeopathic medicine is trimiasmatic, and each remedy has an equal ability to eliminate the disposition to a particular miasm, along with its health issues, provided it's right. Thus, no particular set of remedies, like nosodes, or any other, is needed to deal with them specifically. So, next time your homeopath talks foolish on miasms, you have the right info with you to give it back right to him.
(A detailed understanding on miasms and their meanings, and what Hahnemann meant by it (very important), as portrayed above, can be understood from the book, The End of Myasmtion of Miasms - Predictive Homoeopathy Part 3. Also, a comprehensive yet easily understandable detail on miasms, including all the false information and aura around them, with their reasons, can be had from chapter 5 of my work.)