Patients with active RAS have an increased proportion of gamma-delta T cells compared with controls and patients with inactive disease. Lymphocytes of RAS patients have reactivity to a peptide of Mycobacterium tuberculosis . There is some cross-reactivity between the 65kDa hsp and the 60kDa human mitochondrial hsp. Monoclonal antibodies to part of the 65kDa hsp of M tuberculosis react with Streptococcus sanguis . There is a slight female predominance.
Diagnosis is based on history and clinical features.
Coeliac disease Crohn disease Neumann bipolar aphthosis, where genital ulcers may also be present Behcet syndrome, where there may be genital, cutaneous, ocular, and other lesions. The mouth ulcers in Behcet syndrome are often major aphthae with frequent episodes and long duration to healing. Hypersensitivity reactions to exogenous antigens other than gluten do not have a significant etiological role in RAS, and associations with atopy are inconsistent. Local physical trauma may initiate ulcers in susceptible people, and RAS are uncommon where mucosal keratinization is present or in patients who smoke tobacco. A consistent association between aphthouslike ulceration and psychological illness, zinc deficiency, altered female sex, or corticosteroid use is unlikely.