Halitosis in a child with NF1

My son is 8 and has NF1 which was diagnosed at 18mths old. Physically he is a tall child for his age (95th %) and slightly underweight (75th %).

Physically he has few symptoms with the exceptions of cafe-o-lait spots, anxcillary freckling and some very tiny nodules.  He also has both fine and gross motor skills problems including tactile defensiveness (which is improving with age), problems with muscle association and dysassociation in function, it exhibits as a lack of coordination (ie difficulty catching a ball, difficulty with eye / head dysassociation etc). He is being treated with occupational therapy and gymnastics and also sees an optometrist.  He also has ADHD and is on straterra (25mg once a day).

He has some minor learning delays primarily associated with remembering things in the short term but once he has "got" a concept he is like an elephant and never forgets.

He has had three sets of grommets at 18mths, 2.5yrs and 4yrs.  He also had his tonsils out at 6yrs and they checked his adnoids at the time and found they were regressing with no sign of infection.  His speech was delayed and he has had speech therapy to increase his language (early) and to improve his pronounciation (now).  He has had to be trained to make some sounds and his tongue appears to be affected by the same muscle control problems as the rest of his body.  He does tend to breath through his mouth.

Other than that he is a healthy active child.  The problem is he has dreadful halitosis and has had it for as long as I can remember.  His doctors don't seem to be concerned but they are not the child who has to socially interact with other kids.  He is already socially inept as he is conscious of his speech problems and I prefer this is not compounded by bad breath.

Given we have eliminated infection issues in his nasal and throat cavity, and his dental hygiene is good (brushes, flosses, uses mouth wash & had regular dental checks) could you please suggest some reasons as to the cause of his dreadful breath that I could raise his GP, pediatrician or neurologist.

Thanks

DM