Here is a summary of the lecture on immune-mediated oral conditions.
🧬 Introduction to Immune-Mediated Disorders
Immune-mediated diseases occur when the body fails to distinguish its own cells from foreign antigens, leading to an aggressive reaction against itself. The clinical presentation of these conditions can vary significantly between individuals due to factors like genetic predisposition. Oral lesions can present as ulcers (a complete loss of epithelium), erosions (a partial loss), or atrophy (a thinning of the epithelium). While trauma is the most common cause of oral ulcers, immune-related disorders are another significant cause.
Allergies and Hypersensitivity Reactions
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Allergic Contact Mucositis (Stomatitis): This is an inflammatory reaction caused by direct contact with an allergen. Common dental allergens include latex, oral hygiene products, denture acrylics, and metals. The reaction can appear as red, swollen, or thinned areas, and some products may cause the top layer of the mucosa to slough off easily.
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Plasma Cell Gingivitis: This is a distinct allergic response characterized by a bright red, diffuse enlargement of the gingiva. It is often linked to hypersensitivity to ingredients in oral health products.
Recurrent Aphthous Ulcers (RAUs)
RAUs are episodic ulcers that occur almost exclusively on nonkeratinized (movable) mucosa, such as the inside of the cheeks and lips. They are typically painful, sharply defined, and covered by a yellow fibrin membrane with a red halo. While the exact cause is unknown, they are associated with trauma and stress. There are three main forms:
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Minor RAUs: The most common form (80%), these ulcers are small (
cm), usually appear as one or two lesions, and heal in 1-2 weeks without scarring.
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Major RAUs (Sutton’s Disease): This is the least common form. The ulcers are large (
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Herpetiform RAUs: This uncommon form presents as numerous (more than 10) small ulcers that often merge to form large, extremely painful ulcerated surfaces.
Key Autoimmune Blistering Conditions
Lichen Planus
Lichen planus is a common, chronic inflammatory disorder that affects the skin and mucous membranes. It is considered a T-cell mediated autoimmune response (Type IV hypersensitivity) where lymphocytes attack the basal layer of the epithelium. A key feature is that the lesions are typically bilateral and symmetrical.
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Clinical Forms: The most common form is reticular, which presents as a network of fine, white, interlacing lines known as Wickham’s striae. Other forms include erosive, ulcerative, and atrophic, which are often painful.
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Malignant Potential: Oral lichen planus, especially the erosive type, is considered an oral potentially malignant disorder (OPMD) and requires long-term follow-up with a specialist.
Pemphigus Vulgaris
This is a potentially life-threatening autoimmune disease where the body produces autoantibodies against desmogleins, which are proteins that form the desmosomes holding epithelial cells together.
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Pathophysiology: The attack on desmosomes causes epithelial cells to separate from each other, a process called acantholysis. This results in a fragile, intraepithelial blister (a split within the epithelium). Biopsies show individual keratinocytes called Tzanck cells floating apart.
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Clinical Features: Patients develop fragile blisters (bullae) that rupture very easily, leaving large, painful ulcers. Oral lesions often appear before skin lesions.
Mucous Membrane Pemphigoid (MMP)
MMP is an autoimmune disease where autoantibodies attack proteins in the basement membrane, which acts as the “glue” holding the epithelium to the underlying connective tissue.
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Pathophysiology: This attack causes a clean split between the full thickness of the epithelium and the connective tissue, resulting in a subepithelial blister.
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Clinical Features: Because the roof of the blister is the entire epithelium, it is stronger and less prone to rupture than in pemphigus. A key clinical feature in both MMP and pemphigus is Nikolsky’s sign, where gentle pressure can induce blister formation.
Other Important Lesions
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Traumatic Ulcerative Granuloma with Stromal Eosinophils (TUGSE): This is a specific type of deep, non-healing ulcer that can be mistaken for squamous cell carcinoma, often appearing on the tongue. Its key diagnostic feature is the presence of a large number of eosinophils in the tissue biopsy.
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Erythema Multiforme (EM): This is a self-limiting disease that causes skin rashes and painful oral ulcerations. A severe form, Stevens-Johnson syndrome, involves widespread lesions on the skin, oral cavity, eyes, and genitals.