Hi. Sorry to hear about your friend. If the roof of her mouth eroded and it was extremely painful then that sounds more like she had a midline granulomatous destructive disease such as Wegener's Granulomatosis or lymphomatoid granulomatosis. These are degenerative conditions due to abnormal immune system in the body. She may have had a burning mouth syndrome
(BMS) too but it is very unlikely for the BMS to completely erode the roof of the mouth.
Moderate to severe burning in the mouth is the main symptom of BMS and can start suddenly for no apparent reason and sometimes persist for months or years.
The most common cause for BMS is if there is damage to nerves that control pain and taste. As age progresses, the nerves supplying the cheek tend to lose their protective covering and start to misfire normal signals in the form of burning sensations. This is called as neuropathic pain
(Burning, sore feeling).
Many factors either individually or in combination can lead to this damage to the nerves such as hormonal changes due to menopause or dry mouth, which can be caused by many medicines, hormonal changes and disorders such as Sjögren’s syndrome or diabetes. Nutritional deficiencies especially vitamin B1,B2 and B12 can cause nerve damage
and delay their healing. Some of the other less common causes are oral candidiasis
, a fungal infection
in the mouth, acid reflux
, poorly-fitting dentures or allergies to denture materials, anxiety and depression
Some of these causes such as an advanced fungal disease (Invasive type) can cause erosion of the roof of the mouth. Hope this answers your query.