Aphthous stomatitis caused by a reduction in numbers of CD4+ T cells may be implicated in RAS-type ulceration in HIV infection. 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
Aphthous stomatitis history, suggesting that some people are genetically predisposed to suffering with oral ulceration. HLA-B12, HLA-B51, HLA-Cw7, HLA-A2, HLA-A11, and HLA-DR2 are examples of human leukocyte antigen types associated with aphthous stomatitis. However, these HLA types are inconsistently associated with the condition, and also vary according to ethnicity. People who have a positive family history of aphthous stomatitis tend to develop a more severe form of the condition, and at an earlier age than is typical. Stress has effects on the immune system, which may explain why some cases directly correlate with stress. It is often stated that in studies of