The relative increase in percentage of CD8+ T cells, caused by a reduction in numbers of CD4+ T cells may be implicated in RAS-type ulceration in HIV infection. Mucosal barrier
The thickness of the mucosa may be an important factor in aphthous stomatitis. Usually, ulcers form on the thinner, non-keratinizing mucosal surfaces in the mouth. Factors which decrease the thickness of the mucosa increase the frequency of occurrence, and factors which increase the thickness of the mucosa correlate with decreased ulceration.The nutritional deficiencies associated with aphthous stomatitis (vitamin B12, folate, and iron) can all cause a decrease in the thickness of the oral mucosa (atrophy).Local trauma is also associated with aphthous stomatitis, and it is known that trauma can decrease the mucosal barrier. Trauma could occur during injections of local anesthetic in the mouth, or otherwise during dental treatments, frictional trauma from a sharp surface in the mouth such as broken tooth, or from tooth brushing.Hormonal factors are capable of altering the mucosal barrier. In one study, a small group of females with aphthous stomatitis had fewer occurrences of aphthous ulcers during the luteal phase of the menstrual cycle or with use of the contraceptive pill. This phase is associated with a fall in progestogen levels, mucosal proliferation and keratinization. This subgroup often experiences remission during pregnancy. However, other studies report no correlation between aphthous stomatitis and menstrual period, pregnancy or menopause.Aphthous stomatitis is more common in people who smoke, and there is also a correlation between habit duration and severity of the condition.
Major aphthous ulcers (major aphthae) are similar to minor aphthous ulcers, but are more than 10 mm in diameter and the ulceration is deeper. Because the lesions are larger, healing takes longer (about twenty to thirty days), and may leave scars. Each episode of ulceration usually produces a greater number of ulcers, and the time between attacks is less than seen in minor aphthous stomatitis. Major aphthous ulceration usually affects non-keratinized mucosal surfaces, but less commonly keratinized mucosa may also be involved, such as the dorsum (top surface) of the tongue or the gingiva (gums). The soft palate or the fauces (back of the throat) may also be involved, the latter being part of the oropharynx rather than the oral cavity. Compared to minor aphthous ulceration, major aphthae tend to have an irregular outline. Herpetiform ulceration
Herpetiform ulcers, (also termed stomatitis herpetiformis, or herpes-like ulcerations) is a subtype of aphthous stomatitis so named because the lesions resemble a primary infection with herpes simplex virus (primary herpetic gingivostomatitis). However, herpetiform ulceration is not caused by herpes viruses. As with all types of aphthous stomatitis, it is not contagious. Unlike true herpetic ulcers, herpetiforme ulcers are not preceded by vesicles (small, fluid-filled blisters). Herpetiforme ulcers are less than 1 mm in diameter and occur in variably sized crops up to one hundred at a time. Adjacent ulcers may merge to form larger, continuous areas of ulceration. Healing occurs within fifteen days without scarring. The ulceration may affect keratinized mucosal surfaces in addition to non keratinized.