Apart
from the erosive and bullous forms of the disorder, lichen planus is quite frequently
an indolent.
Painless lesion that
many times has been present in a patient’s mouth long before it is recognized
during a routine dental examination or by the patient noticing that the check
or lip mucosa is rougher than usual.
The clinical features of the lesions in a given patient often vary with time,
both in terms of the morphology of the clinical lesion and its extent and the
area of erosion of the atrophic mucosa.
The reticular form consists
of slightly elevated, fine, whitish lines that produce either a lacelike lesion,
a pattern of fine radiating lines, or annular lesions.
This is the most
common and most readily recognized form of lichen planus, and the only form notd
in more than one of the population surveys reported over the past 30 years.
Most patients with lichen planus at sometime exhibit some areas of the reticular
form. The cheeks and tongue are preferentially affected in many patients with
lichen planus, the lips, gingivae, floor of the mouth, and palate are less frequently
involved.
Because reticular lesions are the most common form, they are
seen most often on the cheek and tongue, in many cases as bilateral lesions.
In the popular form, 0.5 to 1mm whitish elevated lesions, or papules, are
usually seen on the well keratinized areas of the oral mucosa, but large plaque
like lesions that are often difficult to distinguish from leukoplakia may occur
on the cheek, tongue and gingivae.
Papular,
plaques like, atrophic and erosive lesions are very frequently accompanied by
reticular lesions. A search for these is an essential part of the clinical evaluation
of a patient with suspected lichen planus, and when biopsy provides only a non-specific
diagnosis (e.g., acute and chronic inflammation).
The diagnosis of lichen
planus is often confirmed by identifying an area of reticular pattern, even though
at times only a small flame like patch or radially arranged white lines is found.
Characteristically, the affected areas of the oral mucosa are not bound
down or rendered inelastic by lichen planus, and the keratotic white lines cannot
be eliminated either by stretching the mucosa or rubbing its surface.
Reticular and popular lesions are generally asymptomatic, atrophic, erosive and
bullous forms are generally associated with pain.Atrophic lichen planus involving
the gingivae is often referred to as desquamative gingivitis.
A descriptive
clinical term used for bright red, edematous patches involving the full width
of the attached gingivae, which must be distinguished histologically from similar
lesions occurring in some patients with mucous membrane pemphigoid and pemphigus.
An association has been described between oral lichen planus, diabetes
mellitus and hypertension. This triad is referred to as grinspan’s syndrome
and has been suggested as predisposing to the development of squamous cell carcinoma.
Subsequent investigation of other series of patients with lichen planus
have not confirmed grinspan’s finding, other than that a proportion of patients
with chronic oral problems especially those attending hospital clinics will be
found to have diabetes and hypertension.
Lichen planus has also been
described in association with autoimmune diseases.Three features are considered
essential for the histopathologic diagnosis of lichen planus, areas of hyperparakeratosis
or hyperorthokeratosis,
Often with thickening of the granular cell layer
and a saw tooth appearance to the rate pegs, liquefaction degeneration or necrosis
of the basal cell layer, which is often replaced by an eosinophilic band, and
a dense subepithelial band of lymphocytes.
The main diagnostic feature
that lichen planus shares with other lichenoid reactions is damage to the basal
cell layer, including both vacuolar changes and cell death.
Vacuolar
change is characterized by intra-cellular vacuolar, edema, separation of basal
cells, and detachment of the lamina propria from the basal cells.
Artifactual
tears at this level are often seen in specimens mounted for light microscopy,
raising the possibility of a vesiculobulous lesion, and bullae develop at this
level in bullous lichen planus.
The epidermal cell death noted in this
disorder usually involves single basal cells, which are shrunken with eosinophilic
cytoplasm and one or more pyknotic nuclear fragments.
These dead cells
are referred to as Civatte bodies, and there is ultrastructural evidence that
they develop by a process of apoptosis, by which cells are converted to filamentous
bodies that are phagocytosed by macrophages or adjacent basal cells.
Apoptosis eveokes little inflammatory reaction, compared with cell death by necrosis,
and the cells undergoing apoptosis in the basal layers of lichenoid ipithelium
are elsewhere often referred to as dyskeratotic cells.
