I sorta explained all this process in comments on another post but I thought I'd clarify here. 

Since Aiden has Aplastic Anemia he has less bone marrow (5 to 20%). This means his regimen of chemo was 6 days of intense amounts of about 4 or 5 different chemos. (Some others that I've met have longer amounts of days and radiation). Aiden didn't have to have radiation. 

Day 0 they gave him the transplant of new cells through an iv that goes to his heart. The heart pumps and sends the marrow to his bones. 

They needed the chemo to basically kill any remaining bone marrow/immune system he had so it won't try to kill the new stem cells.  (Host vs graft) 

The effects of chemo kills any white cells to give his body a chance to grow new marrow. But without white cells you have certain places in your body that replenish new cells every 5 to 7 days.  Your mouth,  throat,  digestive systems.  White cells heal this area by providing new cells. The same thing for hair loss which we should see soon... right now he's still got his curly head. 

We are day +5 after transplant. He has no white cells to replace those cells.  Last night at 2 am he woke up sobbing,  his throat is burning..hurts to swallow at all.  

Its called mucisidus. They gave him strong pain meds.  Today they put him on a pain pump. He's comfortable but we got very little sleep last night. I'm seeing naps today for sure! 

The only cure for mucisidus is new white cells to heal it.  He has a feeding tube they put in early before this set in knowing this was coming.  

So Day +10 to +21 we should start seeing some increase in white cells and other blood levels.  We just keep him comfortable and safe from infection until his body starts making new cells.  

They are also giving him medicines to prevent graft (the new marrow) from attacking the host.. so it can go both ways... he can attack the graft, or the new graft attacks him.. usually giving him rashes or gut issues. But they have lots of medicines to reduce the chances and reduce side effects.  

I cannot say how appreciative I am to UCSF Bone marrow transplant team.  They've known everything that's coming and work quick to help.  I'm so happy we are in the best place.  

Thank you for continuing to pray for us... now this waiting has become a little more complicated and uncomfortable but God is here.  He sees,  He comforts.  God's got this and He's going to start that bone marrow growing soon!