My oldest son (4y) has also a rare genetic disorder (18q12.3q21.1 deletion). Part of the chromosome that is missing is the SETBP1 gene [1] and this deletion can result in developmental delay, reduced speech and motor skills, intellectual disability and other issues such as autism. My son’s speech for example is limited to simple consonant-vowel syllables. Dr. Angela Morgan, who is mentioned on the IDefine website, is…
Just chiming in as my son too has an 18q deletion, albeit further towards the distal arm. Just to bring to your attention, if you were not already aware, of https://www.chromosome18eur.org and its parent organisation https://www.chromosome18.org.
Some great resources and there'll be folks who have experienced similar issues to you and yours.