1. Dermatological causes of white patches
 Lichen planus:
Lichen = primitive plants composed of symbiotic algae and fungi
Lichen planus = dry lichen-like appearance of affected skin
It is the commonest dermatological disease that may result in oral white
lesions
It is a chronic mucocutaneous disease that involves skin and mucous
membranes
Clinical features:
 Skin lesions:
o Site: any area in the skin may be involved but the commonest site
is the flexer surface of the wrist
o Fingernails may be involved mostly with vertical ridging in 10%
of the cases
o Scalp might be affected in females leading to alopecia
o Clinical appearance:
- Purple, pruritic, papules (PPP) with white streaks on
the surface “Wickham’s striae” which are
characteristic of this condition
- Papule = circumscribed solid elevation of skin with no
visible fluid
- Papules show variable patterns (discrete, linear,
annular, bullous)
- Lesions may also present as widespread rash (in which
skin gets warm, swollen, and maybe painful)
o Lesions develop slowly and 85% of them resolve in almost 18 months, however lesions may
recur in some patients
** When lesions go they leave a pigmented scar behind that take considerable time to resolve
 Oral lesions:
o In contrast to skin lesions, oral lesions pursue a much more chronic course, sometimes
extending over many years (average duration 4.5 years)
o May occur alone or in combination with skin lesions
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2. o Site: lesions mostly affect buccal mucosa (90%), but may also affect the tongue, gingiva,
palate, and lips. The floor of the mouth involvement is relatively uncommon
o Lesions are often bilateral and show wide spectrum of presentations
o Clinical appearance:
- Non-erosive lesions:
 Reticular, annular, papular, plaque-like
** Reticular lesions have white streaks arranged in lace-like pattern
** Plaque-like lesions are white patches resembling leukoplakia clinically
** Papular lesions are small white papules that may coalesce
** Bullous lesions are subepithelial bullae
 They are usually asymptomatic
 They may show hyperkeratosis with NO atrophy & NO ulceration
Reticular Annular Papular Plaque-like
- Erosive/atrophic lesions:
** Erosive lesions are extensive areas of shallow ulceration
** Atrophic lesions are diffuse red lesions resembling Erythroplakia
 Erosion and atrophy are usually present together and lesions have a red glazed
appearance with areas of superficial ulceration which may take several weeks to heal
 Occasionally, ulcers are preceded by bullae (bullous type) that then rupture
 Lesions are often associated with typical areas of non-erosive lichen planus
 They are usually symptomatic
 Pain and discomfort may be severe (especially when eating spicy/acidic foods)
- Gingival lesions:
 Lichen planus involving the gingiva often presents as a desquamative gingivitis
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3.  Desquamative gingivitis is a clinical descriptive
term that doesn’t infer any specific underlying
pathology (so that it has many causes!)
 Gingival lesions may occur alone (in 10% of
cases) or with other oral lesions
Prevalence:
o Lichen planus is a relatively common disease (affects 0.5-2% of general population)
o There's a worldwide distribution
o Peak incidence is found between ages 30-50
o Lesions are more common in females (60% of cases)
o Oral lesions are detected in ~50% of patients with initial skin lesions
o Skin lesions are detected in ~10-50% of patients with initial oral lesions!!
This may be due to:
- Asymptomatic nature of oral lesions in many cases
- Inconstant relationship of oral and skin lesions (oral lesions may occur BEFORE, AFTER
or AT THE SAME TIME as skin lesions)
Histopathological features:
o Orthokeratosis or Parakeratosis
o Epithelial atrophy or acanthosis
o Acanthosis results in irregular elongation and widening
of the rete ridges in a “saw-tooth pattern”
o Dense, well-defined band of subepithelial mononuclear
infiltrate (mainly T-lymphocytes)
o Liquefactive degeneration of the basal cell layer with
edema and lymphocytic infiltration
o The degenerating cells appear as hyaline shrunken bodies,
called Civatte bodies
o Basal cell degeneration may result in subepithelial bullae
formation and ulceration because of the lack of cohesion
between epithelium and lamina propria following the
degeneration
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4. o Oral lesions may show little superficial resemblance to skin lesions clinically even though the
basic histological changes are similar, because of the modifying environment of the oral cavity
by:
- Continuous presence of saliva
- Secondary infection by oral organisms
- Repeated trauma
o Almost all cases run a benign course
o Malignant transformation has been described in a very small proportion (0.5%-2.5% over 5 years)
o Some studies suggest that atrophic/erosive forms are more likely for such transformation
because of the decreased barrier presented to potential carcinogens
o Other studies found malignant transformation more likely with plaque lesions
Etiology & pathogenesis:
o It is NOT fully understood
o In most cases the precipitating factors are unknown and the disease is Idiopathic
o It is widely accepted that cell-mediated immune responses to an external antigen, or internal
antigenic changes in epithelial cells, are involved since response resembles type IV
hypersensitivity reaction which is T-cell mediated
o Cytotoxic lymphocytes damage the basal epithelium
** Possible immunological mechanism in lichen planus:
External antigen challenge and/or modified antigenic structure of epithelial cells  induces
cytokines release from langerhans cells & keratinocytes  chemotaxis of lymphocytes which
accumulate in the basement membrane zone & basal epithelium  antigen presentation to CD4
helper cells  activation of CD8 Cytotoxic cells  basal cell degeneration
o Lichen planus has been associated with some systemic diseases, in many of these, a cause-and-
effect relationship has not been established (e.g. there is strong association of the disease with
chronic liver disease especially hepatitis C virus)
o Oral & skin lesions resembling lichen planus are also seen as a part of graft-versus-host
reaction (immune reactions in patients receiving transplants), in such cases, the transplanted T
cells react to antigens on host epithelial cells
o Lichenoid reaction:
- Lichenoid = lichen-like
- In some patients, lesions similar to lichen planus may appear
triggered by hypersensitivity reaction (IV) to certain drugs
(NSAIDs) or dental materials (amalgam)
- These lesions are clinically and histologically similar to
Lichen planus, but tend to be reversible so that they resolve
upon withdrawal of the offending agent
** Lichenoid reactions aren't idiopathic as lichen planus
** Lichenoid reactions are usually unilateral while lichen planus is usually bilateral
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5.  Lupus Erythematosus (LE):
It is a chronic mucocutaneous disease that involves skin and mucous membranes and believed to be
due to an autoimmune process
It has two main forms:
1. Chronic discoid lupus erythematosus  localized
2. Systemic lupus erythematosus  disseminated
Lesions are more common in females
Clinical features:
1. Chronic discoid lupus erythematosus (DLE):
o It is the localized form of the disease in which skin lesions occur without any systemic
involvement
o Site: lesions are usually restricted to the skin, and confined to the face
o Clinical presentation:
- Skin lesions:
 Lesions appear as scaly or crusted red patches that heal with scar
 Sometimes facial lesions have a symmetrical distribution over the nose and cheek,
the so-called (butterfly rash)
** This butterfly rash can be seen in both forms
 Follicular plugging “hair follicles being plugged and prevented from going out and
growing leading to hair loss)
- Oral lesions:
 Lesions are found in up to 50% of cases
 Buccal mucosa is most frequently affected
 There's considerable variation in the usual
presentation of oral lesions but the most common
is a discoid area of Erythema or ulceration
surrounded by white Keratotic border
sometimes with radiating striae (resembling
lichen planus)
o Histopathology:
- Orthokeratosis or Parakeratosis
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6. - Epithelial atrophy or acanthosis
- Keratin plugging
- The subepithelial lymphocytes are aggregated
in follicles and don’t show the clear band-like
arrangement as in lichen planus
- Liquefactive degeneration of basal cells
- Circulating autoantibodies are found in one-
third of patients
2. Systemic Lupus Erythematous (SLE):
o It is the disseminated form of the disease in which
skin lesions occur with systemic involvement
o Site: skin lesions typically affect the face
“cheeks” and the hands
o Photosensitivity may be implicated in lesions
eruption
o May be fatal
o Clinical presentation:
- Skin lesions:
 Skin rashes (maculopapular)
 Sometimes facial lesions have a symmetrical distribution over the nose and cheek,
the so-called (butterfly rash)
- Oral lesions:
 They are variable
 Superficial erosions and erythematous patches on the buccal mucosa
 White Keratotic areas are not so frequently seen as in DLE
o Histopathology:
- Non specific diffuse inflammatory infiltrate
- A variety of circulating autoantibodies are almost always present (e.g. antinuclear
antibodies (ANAs))
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