Electron microscopic study on the pathogenesis of recurrent aphthous ulceration as compared to Behçet's syndrome

Mucosal disease series. Number VI. Recurrent aphthous stomatitis

Recurrent aphthous stomatitis (RAS; aphthae; canker sores) is a common condition which is characterized by multiple recurrent small, round or ovoid ulcers with circumscribed margins, erythematous haloes, and yellow or grey floors typically presenting first in childhood or adolescence. RAS occurs worldwide although it appears most common in the developed world. The aetiology of RAS is not entirely clear. Despite many studies trying to identify a causal microorganism, RAS does not appear to be infectious. A genetic predisposition is present, as shown by strong associations with genotypes of IL-1beta; IL-6 in RAS patients, and a positive family history in about one-third of patients with RAS. Haematinic deficiency is found in up to 20% of patients. Cessation of smoking may precipitate or exacerbate RAS in some cases. Ulcers similar to RAS may be seen in human immunodeficiency virus disease and some other immune defects, and drugs, especially non-steroidal anti-inflammatory drugs and nicorandil may produce lesions clinically similar to RAS. Topical corticosteroids can often control RAS. However, the treatment of RAS remains unsatisfactory, as most therapies only reduce the severity of the ulceration and do not stop recurrence.

Recurrent aphthous stomatitis

Recurrent aphthous stomatitis (RAS) is one of the most common oral mucosal disorders. Nevertheless, while the clinical characteristics of RAS are well-defined, the precise etiology and pathogenesis of RAS remain unclear. The present article provides a detailed review of the current knowledge of the etiology, pathogenesis, and management of RAS.

Clinical, historic, and therapeutic features of aphthous stomatitis. Literature review and open clinical trial employing steroids

The clinical and historic features of 50 patients with diagnosed aphthous stomatitis and treated with topical triamcinolone acetonide, 0.1% or 0.2% aqueous suspension; alone or in combination with initial burst therapy of 40 to 60 mg of prednisone, are reviewed. The mean age of our patients was 36.6 years (range 6 to 80 years). The duration of the chief complaint, usually oral pain, or more specifically, recurrent oral ulcers, was 11.1 years (range 4 weeks to 40 years). All patients showed a wide range of ulcer sizes when examined initially or at follow-up. Forty were followed up for an average of 22.9 months. Thirty-four reported prompt healing of ulcers identified at the time of initial evaluation, and no or markedly fewer ulcers subsequently if maintenance therapy of prophylactic topical triamcinolone, 0.1% or 0.2% aqueous rinse, was used. Five patients reported partial relief. No systemic side effects were noted even after long-term topical therapy. Local candidosis was a complication encountered in five patients.

Are recurrent oral aphthous ulcers of viral etiology?

The etiology of recurrent oral aphthous ulcers (RAU) remains unsolved. The present article relates previous immunopathologic findings in RAU to a possible viral etiopathogenesis with special reference to the herpes virus family. It is concluded that RAU might be of viral etiology, and it is furthermore speculated that the aphthous ulcers may be the clinical manifestation of 'latent' varicella-zoster virus reactivation (reinfection).

Recurrent aphthous stomatitis: current concepts of etiology, pathogenesis and management

Recurrent aphthous stomatitis (RAS) is a common oral disorder, however, despite detailed clinical, immunologic, hematologic and microbiologic investigation, the etiology of RAS remains unknown. At present, topical steroids and antimicrobial mouth rinses are the mainstays of treatment, but there is still no means of preventing recurrence of the oral ulceration.

The proportion of suppressor-inducer T-lymphocytes is reduced in recurrent aphthous stomatitis

A flow cytometric analysis of peripheral blood lymphocytes was undertaken in recurrent aphthous stomatitis patients. The project aimed at detecting differences within lymphocyte subsets using type-specific monoclonal antibodies. Peripheral blood samples were taken from RAS patients in both active and remission phases of the disease and from a group of healthy control subjects. There were no statistical differences between the active and remission phases within any of the lymphocyte subsets examined. There was, however, a significant difference between the RAS group and the control group. RAS patients have depressed CD4+ cell numbers and elevated CD8+ cell numbers. The CD4:CD8 ratio is also depressed. A dissection of the CD4+ subset shows raised numbers of CD4+, 4B4+ lymphocytes and depressed numbers of CD4+, 2H4+ lymphocytes. Previous studies have shown disruption of peripheral blood lymphocyte numbers in Behçet's syndrome. A similar pattern has now been shown in uncomplicated cases of minor RAS.

Natural killer cell numbers and function in peripheral lymphoid cells in Behcet's disease

We have studied NK cell activity and numbers in the peripheral blood obtained from patients with Behcet's disease and from normal healthy controls. NK cell activity in the peripheral blood of patients in the clinically-active stage of Behcet's disease was significantly lower than that of patients in the inactive stage and normal controls. In contrast, it was observed that the actual number of NK cells was markedly increased in the peripheral blood of patients with active disease. The addition of alpha-interferon (INF-alpha) to these cells showed significant augmentation of NK cell activity. These results suggest that the patients with active Behcet's disease lack a factor which activates NK cells.

Immunological studies on aphthous ulcer and erythema nodosum-like eruptions in Behcet's disease

Patients with Behcet's disease show an intense delayed hypersensitivity (DH) reaction to a group of streptococcal bacteria. We have attempted to detect deposits of immune complexes and to analyse cytological reactions in the aphthous ulcers and erythema nodosum (EN)-like eruptions. Deposits of IgM and positive fluorescence of anti-streptococcal group D serum were found in vessel walls and sites infiltrated by inflammatory cells. Cytological analysis has revealed that the inflammatory infiltrating cells are mainly composed of activated T-cells and macrophages in association with natural killer cells. These results suggest that DH reactions with antigen-antibody mediated cytotoxicity may play an important role in causing the lesions of Behcet's disease.

Possible role of apoptotic cells of the oral epithelium in the pathogenesis of aphthous ulceration

Electron microscopic examination of the normal oral mucosa of patients with recurrent aphthous ulceration or Behçet's syndrome revealed that the degenerate dark prickle cells are apoptotic cells. Such dark prickle cells showed characteristic findings of apoptosis, such as the shrinkage of nucleus and cytoplasm and the formation of contraction vacuoles. The number of intraepithelial mononuclear cells phagocytosing apoptotic cellular debris increased remarkably at the preulcerative stage of the aphthous lesions. The apoptotic debris also attracted neutrophilic leukocytes in the prickle cell layer at the preulcerative stage but not in the normal oral epithelium. It is speculated that the onset of aphthous ulceration is closely related to phagocytosis of these apoptotic cells by intraepithelial mononuclear cells.

Pathomorphologic features of the ulcerative stage of oral aphthous ulcerations

Macroscopic, histopathologic, and immunohistochemical features of eight 1- to 7-day-old minor (Mikulicz) aphthae, one herpetiform ulcer, and one ulcer from a patient with Behcet's syndrome were studied. In addition to light and electron microscopy, methods included the peroxidase-antiperoxidase (PAP) technique to disclose binding of IgA, IgG, IgM, Clq, and C3. Observations revealed the presence and distribution of extravasates of erythrocytes at and around the ulcers, extravascular neutrophilic granulocytes undermining the oral epithelium of the ulcer margin, the presence of numerous macrophages loaded with phagolysosomes containing debris of neutrophilic granulocytes, particular pathomorphologic features of a Behcet lesion and a herpetiform lesion, and the occurrence in diseased and normal oral mucosa of particular stratum spinosum cells binding nonselectively all immune components tested in this study, probably by leakage and passive diffusion of serum proteins. The observations fit the concept of immune complex vasculitis being essential in the pathogenesis of oral aphthous ulcerations.

Stereologic analysis of leukocyte infiltration in oral ulcers of developing Mikulicz aphthae

Biopsy specimens of 1- to 7-day-old oral ulcers from patients with minor (Mikulicz), herpetiform, and Behcet's aphthae and of nonulcerated oral mucosa of aphthous patients were subjected to a quantitative, stereologic, electron microscopic analysis of the connective tissue infiltrate residing both at the center of and lateral to the ulcers. The data representing volume fractions and the numerical density of cellular and other infiltrate components demonstrated that (1) the infiltrate under the epithelium lateral to the ulcer is different from that at the ulcer's center, (2) at both sites, composition of the gross infiltrate does not change with age of the ulcer, (3) a large population of leukocytes (about 18% in the lateral and 23% in the central region) belong to the monocyte/macrophage series, (4) blast-forming T-lymphocytes are consistently present, blast-forming B-lymphocytes and plasma cells are very rare, and (5) mast cells are several times more numerous than in normal mucosa. In a comparison of the infiltrates of Mikulicz aphthae with those of herpetiform and Behcet's ulcers, it appears that the pathogenesis of the various oral ulcerations may well be diverse.

Quantitative electron microscopy microscopical analysis of leukocyte infiltration in oral ulcers of Behçet's syndrome

A stereological electron microscopical technique was applied to biopsies of oral ulcers from patients with Behçet's syndrome in order to carry out a quantitative analysis of the cellular infiltrate. The results have confirmed the light microscopical qualitative findings of a large number of lymphocytes (67%) but have established that a relatively large proportion of the leukocytes (14%( belong to the monocyte-macrophage series. The virtual absence of plasma cells during the early stages of ulceration and the presence of a large number of lymphocytes and monocytes argue in favour of a type IV cell-mediated immune reaction. As the lesion progresses a type III reaction develops and this might be associated with immune complexes found in the serum of patients with Behçet's syndrome.

Aphthous ulcers--a review of the literature on etiology, pathogenesis, diagnosis, and treatment

Recurrent aphthous ulcerations are seen in everyday dental practice. These lesions may easily be misdiagnosed and mistreated. A comprehensive but nondefinitive review of the literature is presented in hope that the practitioner can better diagnose, evaluate, research, and treat RAS. Although many modalities of treatment have been advocated, a truly effective therapeutic regimen to prevent RAS does not yet seem available. Additional research on the ideology, pathogenesis, and treatment of RAS is, therefore, needed.

Quantitative distribution of inflammatory cells in recurrent aphthous stomatitis

Histologic quantitation of leukocytes in biopsies of recurrent aphthous ulcers revealed at least two morphologically-distinct inflammatory infiltrates. Lymphocytes were found consistently in pre-ulcerative lesions and in the expanding margins of the developing ulcer. In contrast, polymorphonuclear leukocytes predominated only in areas of frank ulceration.

Interepithelial cells of the oral mucosa. Light and electron microscopic observations in germfree, specific pathogen-free and conventionalized mice

Interepithelial cells are found in all epithelia of the internal and external surfaces of the mammalian body. The regional differences of these interepithelial cells and their function are not completely known so far. The quantitative and qualitative changes of the interepithelial cell population were investigated in germfree, specific pathogen-free and conventionalized mice by light and electron microscopy. Germfree and specific pathogen-free animals did not show significant differences in the number of interepithelial cells. In the epithelium of the tongue a mean of 7.4 cells per 1000 basal cells is found. After conventionalization a significant increase to 14.4 interepithelial cells per 1000 basal cells is observed. The number of cells in the buccal epithelium is constantly about 20% higher than in the epithelium of the tongue. In the oral mucosa lymphocytes, cerebriform cells and Langerhans cells are an integral component of the epithelium. In contrast to the monostratified intestinal mucosal epithelium, which is considered a secondary lymphatic tissue, the interepithelial lymphocytes of the oral mucosa are not significantly decreased in germfree animals. This could indicate that the oral mucosa functions partly as a primary lymphatic tissue. Interepithelial cerebriform cells and Langerhans cells increased after conventionalization with a maximum after 10 days in response to exogenous antigens. Both cells are immunologically important. The observations prove that the oral mucosa represents a local immunologic system in which the Langerhans cells plays an important part by formation a reticulo-epithelial tissue.

Aphthous ulcer--a treatment complication. Report of a case

Multiple theories of the cause and treatment of aphthous ulcers are described in the medical and dental literature. A case is reported in which there were posttreatment sequelae from the application of a sillver-nitrate stick (pencil) to an aphthous ulcer on the tongue. Compications subsequent to the use of silver nitrate may contraindicate the use of this agent in its highly concentrated form on the mucous membranes of the mouth.

Recurrent aphthous stomatitis: clinical characteristics and evidence for an immunopathogenesis

Recurrent aphthous stomatitis is one of the most common diseases affecting the oral mucosa, and one of its variants is the most painful affliction of the oral mucosa. The lesions of recurrent aphthous stomatitis can be manifested as part of a broad spectrum of clinical disease ranging from the common minor aphthous ulcers to Behçet's syndrome. Differential diagnosis, although not often difficult, must include many conditions capable of producing erosive and ulcerative oral mucosal lesions. The salient features of recurrent aphthous stomatitis suggest that it is a heterogeneous entity. Recent immunologic investigations have focused attention on a possible immunopathogenesis and the evidence for this is reviewed.