Why would the Chazon Ish of sacred and blessed memory stand up whenever he saw a Downes or autistic child? He said that their bodies house the souls of tzaddikim who have nothing to rectify, but they come to this world to help us attain our soul correction.
The Chazon Ish's words need no reinforcement, but Marcel Cohen's dream about his brother Aaron is word-for-word the Chazon Ish's principle. This is really poignant:
Warmest regards to two very special children in Mexico City - Sharon Gloria Btesh and Yehoyada Laniado. May Hashem bless them with big miracles!