Thyroid possibly? The thyroid gland is located in the neck, just below the Adam's apple. If it is swollen then it could be interferring with his adams apple.

I would first want to differentiate between sensation of lump in throat and a true physical obstruction/misalignement in his throat that may constrict the trachea.

If it's of physical nature then you may want to consult a good chiropractor to see if his neck/spin is misaligned; certainly looking at any swelling of the glands in the region is wise.

There are many conditions that can trigger sensation of lump in throat. This generally cannot be diagnosed by conventional medicine/bloodwork so you may be knocking at the wrong door if there are no structural issues. I have been thru this route including sticking a camera down my throat to no avail.

Personally I believe that this sensation can be caused by an overly sympathetic response of the body that can leave the body on permanent high alert - this may be due to previous infection/stressful event (surgery can be one); a nervous system that is excessively sympathetic (as opposed to para-sympathetic) is constantly on high alert with excessive worries/fears, unable to relax and adequately cope with day to day events. Generally this progresses into hormonal imbalance conditions like anxiety, adrenal fatigue, CFS,etc.

You may also consider looking at homeopathy and even TCM to understand possible triggers that can create this sensation - these modalities look at this symptom in a very elegant way.

Mike