What's the Name of That Book??? discussion

A science fiction children’s book where a child has a disease and the sibling is miniaturized enough that he/she can go into the diseased body and fight the disease to save his/her sibling.

When did he read it (year)?

I feel like someone has requested this exact book in the past few months but I can't find the thread. You didn't happen to post this request under a different name, did you?

'A Wind in the Door' by Madeline L'Engle. It's a sequel to A Wrinkle in Time.
"It is November. When Meg comes home from school, Charles Wallace tells her he saw dragons in the twin's vegetable garden. That night Meg, Calvin and C.W. go to the vegetable garden to meet the Teacher (Blajeny) who explains that what they are seeing isn't a dragon at all, but a cherubim named Proginoskes. It turns out that C.W. is ill and that Blajeny and Proginoskes are there to make him well - by making him well, they will keep the balance of the universe in check and save it from the evil Echthros.
Meg, Calvin and Mr. Jenkins (grade school principal) must travel inside C.W. to have this battle and save Charles' life as well as the balance of the universe.

A Wind in the Door by Madeleine L'Engle - Sue's suggestion

Julie, are you still looking for this or did you find it?

I found it!!!!! You guys are the best.

Was it Sue's suggestion of A Wind in the Door?

Please let us know the title and author so we can shelve the book.