| Disease or condition | 
        Clinical characteristics | 
      
      
        | Recurrent aphthous stomatitis  | 
        Appearance of ulcers (aphthae) in oral mucosa with yellowish base, surrounded by an erythematous halo and regular margins and that disappear without treatment. Acute course | 
      
      
        | Behçet’s disease | 
        Appearance of aphthae in the oral mucosa with genital and ocular ulcers | 
      
      
        | Eerythema multiforme  | 
        Target-shaped skin lesions, oral erosions, involvement of lips in the form of erosions and crusts | 
      
      
        | Erosive lichen planus | 
        Appearance of Wickham striae and erosive lesions | 
      
      
        | Oral candidiasis | 
        Whitish lesions that detach on scraping and atrophic erythematous areas | 
      
      
        | Acute herpetic gingivostomatitis  | 
        Prodromic symptoms followed by the onset of small yellowish vesicles that rapidly rupture, giving rise to ulcers with an erythematous halo. It affects free and attached g ingiva. | 
      
      
        | Impetigo | 
        Bacterial infection with appearance of skin ulcers covered by a honey-colored crust. It affects face, arms and legs. It is more frequent in children. | 
      
      
        | Disease by linear IgA deposit  | 
        Symmetric blisters and pruritic lesions, target-shaped lesions | 
      
      
        | Mucosal pemphigoid or cicatricial pemphigoid | 
        Possible  manifestation of an underlying malignant disease: oral lesions do not precede skin lesions, and blisters are smaller with a shorter duration than in PV. They heal rapidly without scarring | 
      
      
        | Bullous pemphigus | 
        Vesicles or tension blisters with clear content that develop on normal or erythematous skin; intense pruritus, symmetric lesions that appear on flexion areas, root of extremities, thighs, and abdomen; rare on mucosae. | 
      
      
        | Herpetiform dermatitis | 
        1-3 cm erythemas that infiltrate palate and buccal mucosa; aphthae on labial mucosa. They appear months or years after the appearance of lesions on skin | 
      
      
        | Epidermolysis bullosa | 
        Development of blisters with minimal pressure, ring-shaped atrophic scars on the inner surface of limbs and articulations | 
      
      
        |  Paraneoplastic pemphigus | 
        Autoimmune syndrome associated with lymphoproliferative neoplasm of B cells | 
      
      
        | Erythematous pemphigus | 
        There are usually no oral lesions | 
      
      
        | Pemphigus foliaceus | 
        There are usually no oral lesions | 
      
      
        | Chronic benign pemphigus familiaris  | 
        There are usually no oral lesions | 
      
      
        | Disseminated lupus erythematosus  | 
        Systemic signs (fever, asthenia) normally accompanied by petechiae, edemas and dry mouth | 
      
      
        | Crohn’s disease and hemorrhagic rectal colitis | 
        Mucocutaneous signs accompanied by abdominal pain, aphthae in oral mucosa, asthenia, weight loss, and anorexia | 
      
      
        | Folic acid or vitamin B12 deficiency | 
        Oral pain, erythematous tongue, asthenia and anemia, paresthesias in limbs, and physical problems | 
      
      
        | Hypochromic iron deficiency | 
        Pallor, fatigue, cephalalgias, vertigo, buzzing in the ears, irritability, insomnia, concentration problems, sensitivity to cold, anorexia and nausea | 
      
      
        | Enteropathic acrodermatitis | 
        Loss of taste and smell, sight problems, intense diarrhea, alopecia, and hypertension             |