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© 2004 European Society of Veterinary Dermatology 341
Veterinary Dermatology 2004, 15, 341–348
BlackwellPublishing,Ltd.
A retrospective study comparing the histopathological featuresand response to treatment in two canine nasal dermatoses,
DLE and MCP
S. P. WIEME LT*, M. H. GOL DSCH MIDT†, J. S. GREEK‡, J. G. JEFFERS§,A. P. WIEMELT¶ and E. A. MAULDIN†
*Departments of Clinical Studies and †Pathobiology, University of Pennsylvania,
School of Veterinary Medicine Philadelphia, PA, USA
‡Veterinary Specialists of Kansas City, Overland Park, Kansas, USA
§Animal Dermatology Clinic, Rockville, Maryland, USA
¶Merck Research Laboratories, Merck & Co., Inc., West Point, PA, USA
(Received 4 April 2003; accepted 15 December 2003)
Abstract Canine discoid lupus erythematosus (DLE) and mucocutaneous pyoderma (MCP) have overlapping
clinical and histopathological changes, often making diagnosis difficult. Histopathological features of 27 nasal
planum biopsies were scored to determine whether DLE and MCP were histopathologically distinguishable.
Long-term follow-up, enabling assessment of clinical diagnoses, was available on 15 cases; 11/15 cases were immuno-
modulatory responsive (ImR) and 4/15 were antibiotic responsive (AbR). Clinical diagnosis, determined by
response to treatment for 15/27 cases, was not predictable based on scoring of histopathological features. Distinct
histopathological patterns were observed: 2/11 ImR cases had a lymphocyte-rich interface dermatitis. All other
cases had the same histopathological changes: a band-like diffuse superficial plasmacytic to lymphoplasmacytic
dermatitis± focal basal cell damage, but different clinical diagnoses (4/4 AbR, 9/11 ImR). German shepherd dogs/
crosses were over-represented (44.4% of the cases) and tended to have more multifocal lesions (41.7% vs. 26.7%
of all other breeds). Longer duration of disease was associated with a preponderance of plasmacytic infiltrate
(P = 0.026).
Keywords: canine, discoid lupus erythematosus, interface, lichenoid, mucocutaneous pyoderma.
INTRODUCTION
The differential list for nasal dermatoses is extensive
and includes canine discoid lupus erythematosus (DLE)
and mucocutaneous pyoderma (MCP).1,2 Discrimina-
tion between these two diseases on the basis of histo-
pathology can be challenging, and dermatopathologists
often report only a morphological diagnosis when
observed changes are not overtly characteristic foreither disease.
Canine DLE has been reported in the literature for
more than 20 years,3,4 and is a benign autoimmune
cutaneous disease initially presenting with depigmenta-
tion, erythema, scaling, and a loss of the normal
cobblestone-like architecture of the nasal planum. With
chronicity, lesions may spread up the bridge of the nose,
becoming more extensive to include erosion, ulceration
and crusting. Lesions may be observed, though less
frequently, on periocular regions, pinnae or genitals.1
The infiltrate present in canine DLE is reported to be
predominantly a lymphocyte-rich interface dermatitis
along the dermoepidermal junction, hair follicles and
adnexal glands. However, it is also reported that this
infiltrate can vary from being primarily lymphocytic
to lymphoplasmacytic and in some cases primarily
plasmacytic. This infiltrate may partially obscure the
dermoepidermal junction and may occur around
superficial and deep vessels. Vacuolar degeneration
may be observed, as well as apoptosis of individualkeratinocytes in the basal cell layer (Civatte bodies),
often with marked pigmentary incontinence, lym-
phocytic exocytosis, and focal basement membrane
thickening.2,5,6 The epidermis is usually hyperplastic
but may have focal areas of atrophy.6 Dermal and epi-
dermal mucinosis may be present.6
There is debate whether DLE, a term borrowed from
human medicine, is properly applied when describing
the canine disease.2,7,8 Therefore, in this paper, the term
lupus-like disease of the nasal planum (LLDN) will be
used to describe cases of nasal dermatitis previously
referred to as ‘canine DLE’, having the following
histopathological features: lymphocyte-rich interfacedermatitis with vacuolar degeneration, apoptosis of
basal cells, and varying degrees of epidermal atrophy
and hyperplasia.
Correspondence: E. A. Mauldin, University of Pennsylvania, School
of Veterinary Medicine, 3900 Delancey St., Philadelphia, PA 19104,
USA. E-mail: emauldin@vet.upenn.edu
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© 2004 European Society of Veterinary Dermatology, Veterinary Dermatology, 15, 341–348
In dogs, MCP has been reported as a visibly distinct
process from LLDN, presenting with erythema, swelling
and crusting. With chronicity, depigmentation, fissur-
ing, and erosions (primarily involving the lips and
perioral skin) may develop.2,9 Clinically, MCP resolves
with relatively short courses of antibiotics, although
long-term management may be needed as lesions mayrecur.9 In contrast, LLDN does not respond as readily
to short courses of therapy, but is controllable with
long courses of immunomodulatory treatments. MCP
can affect the nares and nasal planum exclusively, and
in this respect is clinically similar to LLDN.9 In MCP,
the infiltrate is described as a dense band-like super-
ficial dermal infiltrate (‘lichenoid’ in some texts),6 which
is predominantly plasmacytic (vs. lymphocytic in
LLDN), and hugs rather than obscures the dermoepi-
dermal junction.2,5,6 Vacuolar degeneration and apop-
tosis of basal cells, evidence of basal cell damage that
is seen in cases of LLDN, are features not seen in MCP.
Despite these reported differences there are many cases
that display overlapping clinical and histopathological
features of LLDN and MCP, making histopatholog-
ical differentiation difficult.
Adding to the difficulty in defining the histopatho-
logical features and the degree to which they must be
present in order to be diagnostic of one of these two
diseases, the terms interface and lichenoid are used
imprecisely and inconsistently in the literature when
describing the inflammatory infiltrate in the superficial
dermis in LLDN and MCP.5,10 Improper use of these
terms will imply that certain histopathological changes
thought to be specific for one of the two diseases arepresent, when they are not. In this paper, the term
interface dermatitis will be used when the dermoepider-
mal junction is obscured by vacuolar degeneration, by
lichenoid (band-like) cellular infiltrate, or by both. A
pattern of inflammation in the superficial dermis that
does not obscure the basement membrane will be
described as a band-like superficial dermatitis, with
additional qualifiers.
This study was designed to determine whether
LLDN and MCP could be distinguished on the basis
of semiquantitative analyses of histopathological
features.
MATERIALS AND METHODS
Case selection criteriaA computer search was performed for canine nasal
biopsy submissions coded as ‘lupus, discoid lupus,
nasal pyoderma, mucocutaneous pyoderma, nasal,
nasal planum, lichenoid and interface’ from in-house
cases submitted to the Diagnostic Service of the
Laboratory of Pathology and Toxicology, University
of Pennsylvania, School of Veterinary Medicine, and
from submissions to the aforementioned laboratory bytwo board-certified veterinary dermatologists during
the time period 01/1994–09/2002. Cases were limited
to those obtained from the nasal planum; any samples
containing only haired skin or samples from other
mucocutaneous junctions were excluded. All cases of
Vogt–Koyanagi–Harada-like syndrome (VKH), pem-
phigus foliaceus and erythematosus, systemic lupus
erythematosus, nasal hyperkeratosis and allergic/contact
dermatitis were excluded.
Clinical featuresThe medical records were reviewed for all cases. The
following information was recorded: signalment,
lesion distribution, duration of lesions prior to biopsy,
any treatments received at the time of biopsy, response
to treatment (antibiotics, topical or systemic steroids,
tetracycline/niacinamide, and others), all diagnostics
performed and abnormal values, description and
progression of lesions previous to biopsy and after
instituting treatment (including date of last clinical
examination and duration of therapy), and original
diagnosis given by the dermatopathologist.
Determination of clinical response to treatmentCases were determined to be either immunomodulat-
ory responsive (ImR) or antibiotic responsive (AbR)
based on reported response to treatment. Response to
immunosuppressive or immunomodulatory treatment
(consistent with an autoimmune process like LLDN)
was assigned to cases in three different categories: (1)
dogs that were treated with antibiotics for more than
21 days at an appropriate dosage, demonstrated mild
to moderate improvement, and proceeded to demon-
strate nearly complete to complete improvement when
placed on immunomodulatory therapy (topical, inject-able or oral steroids, a combination of tetracycline and
niacinamide often with vitamin E or fatty acids, topical
tacrolimus, and in one case azathioprine); (2) dogs that
received antibiotics in combination with any immuno-
modulatory or immunosuppressive treatments and
whose improvement continued beyond the discontinu-
ation of antibiotics to the level of complete resolution
while on immunomodulatory/immunosuppressive
therapy; (3) dogs that had resolution of lesions on
immunomodulatory or immunosuppressive therapy
without concurrent antibiotics. For all cases receiving
tetracycline, the dosage was suboptimal for bacterio-static effect.
Response to antibiotic treatment (consistent with an
infectious process like MCP, which demonstrates
complete cure with a short course of appropriate anti-
biotics) was assigned to dogs in two different categories:
(1) dogs that demonstrated nearly complete to com-
plete resolution on oral antibiotics ± topical antibiotics;
(2) dogs that demonstrated only mild improvement
on oral steroids, and then demonstrated complete resolu-
tion when given oral antibiotics.
Dogs without follow-up (10/27) or those that were
treated appropriately with antibiotics and/or immu-
nomodulatory drugs and had mild or no improvement(2/27) were assigned to the category ‘no response to
therapy’. Thus, response to therapy was evaluated for
a total of 15/27 cases.
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Comparing Canine DLE and MCP 343
Histopathological evaluationHematoxylin and eosin-stained slides and Periodic
acid-Schiff stained slides from all cases were reviewed
by two of the authors together (SPW, EAM) and were
reviewed independently by a third author (MHG).
Review of each of the slides was performed in a blinded
fashion, without knowledge of history, prior dia-gnoses, therapeutic treatment or clinical outcome.
A prespecified panel of features were examined and given
a numeric score. The histopathological features used to eval-
uate each section were based on those previously proposed
to distinguish LLDN from MCP and are listed below.2,5,6
Features and scoring
Cells present in the infiltrate: 0 = predominantly
plasmacytic; 1.5 = a mixed inflammatory infiltrate
of lymphocytes, plasma cells, and occasional macro-
phages; 3 = predominantly lymphocytic.
Presence of a deep infiltrate around adnexal glands
and vessels: yes/no.
Degree to which the dermoepidermal junction is
obscured : 0 = not obscured; 1 = obscured focally; 2
= obscured multifocally; 3 = obscured diffusely.
Degree of vacuolar basal cell alteration/degeneration:
0 = no vacuolar degeneration; 1 = focal vacuolar
degeneration; 2 = multifocal vacuolar degeneration;
3 = diffuse vacuolar degeneration.
Number of apoptotic basal cells (Civatte bodies) per high
power field : 0 = no Civatte bodies; 1 = 1 per 10 hpf;
1.5 = 1 per 8 hpf; 2 = 1 per 5 hpf; 2.5 = 1 per 2 hpf;
3 = 1 or > per hpf.
Thickening of basement membrane (the basal lamina
zone): 0 = no thickening; 1 = focal thickening;
2 = multifocal thickening; 3 = diffuse thickening.
Degree of pigmentary incontinence: 0 = no inconti-
nence; 1 = mild, only seen focally at high magnifica-
tion; 2 = moderate, seen focally at low magnification;3 = severe, seen diffusely at low magnification.
Presence of epidermal atrophy: yes/no.
Degree of epidermal hyperplasia: 0 = no hyperplasia;
1 = mild, focal hyperplasia; 2 = moderate, multifocal
hyperplasia; 3 = severe, diffuse hyperplasia.
Lymphocytic exocytosis into the epidermis: yes/no.
Statistical analysesNumeric semiquantitative scores for the features described
above were evaluated statistically using the nonparametricMann–Whitney test for random, independent samples
with nominal values. Those features assigned ordinal (i.e.
yes/no) values were evaluated using the chi-square test.
RESULTS
Clinical data
Signalment. Twenty-seven dogs met the selection cri-
teria. There were 15 female dogs (13 spayed), and 12
male dogs (eight castrated). There were 12/27 Germanshepherd dogs (44%; 10 pure-bred and two crosses),
6/27 mix breeds, a springer spaniel, a cocker spaniel, a
field spaniel, a Samoyed, a collie, a Labrador retriever,
a standard poodle, a greyhound, and an Irish wolf-
hound. Age at presentation ranged from 8 months to
13 years (mean: 7.5, SD: ± 0.6 years). The duration of
nasal dermatitis prior to biopsy ranged from 2 to
48 months (mean: 16.9, SD ± 2.8 months).
Lesion distribution. While all cases had nasal lesions,
9/27 dogs had additional lesions at other locations,
including the lip (6), periocular area (2), vulva (1), scro-
tum (1), and the haired skin of the muzzle (2). Multi-
focal lesions were present on 5/12 (41.7%) German
shepherd/shepherd-crosses, and present on 4/15
(26.7%) of all other breeds, although these differences
were not shown to be statistically significant.
Analysed retrospectively, knowledge of the breed of
the animal and presence of multiple lesions did not
appear to significantly influence the originally assigned
histopathological diagnosis.
Lesion description. Of the 27 cases, 24 were reported to
have crusts, 22 with depigmentation, 16 with erythema,
12 with loss of ‘cobble-stone’ architecture, 11 withulceration, seven with erosions, four with pruritus, four
with a recorded history of waxing and waning, three
with fissures, and two with scale. These reported
lesions did not correspond to any other clinical feature.
Follow-up. Follow-up of greater than 8 weeks (median:
12.0 months, range: 2–36 months) was established in
17 cases. There were 14/17 cases that were re-examined
at least once by the original dermatologist, 1/17 that
was re-examined by the local veterinarian, and 2/17
that had a phone-call follow-up.
Eleven of 17 cases were categorized as immuno-modulatory responsive (ImR). Four of 11 dogs
received an adequate dose and course of antibiotics,
but demonstrated resolution of lesions only after
immunomodulatory drugs were started. Five of 11
dogs received a combination of oral antibiotics and
immunomodulatory drugs. These five dogs continued
to demonstrate improvement after cessation of anti-
biotics. One case never received antibiotics (case
#11), and one case (case #10) recovered after receiv-
ing 6 days of ampicillin followed by extended treat-
ment with tetracycline and niacinamide plus topical
betamethasone.
Of these 11 cases, seven were maintained on animmunomodulatory protocol including tetracycline or
doxycycline. Only 4/11 cases did not receive tetracy-
cline as part of an immunomodulatory treatment
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© 2004 European Society of Veterinary Dermatology, Veterinary Dermatology, 15, 341–348
protocol; one case never received any antibiotics
(case #11) and responded completely to oral pred-
nisone; and one case (case #8) was treated with
cephalexin for 6 weeks with moderate improvement,
and subsequently demonstrated complete improve-
ment after discontinuing the cephalexin and starting
topical steroid treatment only. These two cases had a12- and 9-month follow-up, respectively. Another case
(#7) was treated with enrofloxacin and then amoxicil-
lin trihydrate/clavulanate potassium with no improve-
ment. Resolution was then achieved on 0.1%
tacrolimus. The last case (#9) had a moderate response
to sulfadimethoxine/ormetoprim, and then a complete
response to oral steroids. Due to the retrospective
nature of the study the terms ‘complete response’ or
‘resolution’, as given in the record, could indicate that
the appearance of the nasal planum had returned
to normal, or that a dramatic improvement in lesions
was observed and additional improvement was not
expected. All 11 cases were either maintained on
immunomodulatory therapy or, in cases where it was
discontinued, lesions became worse and immuno-
modulatory treatment had to be re-instituted, indicating
that in these cases the disease process was controllable
but not curable.
Four of 17 cases were antibiotic responsive (AbR).
The duration of antibiotic treatment ranged from
4 weeks (case #12) to greater than 10 weeks (case #15).
One dog improved mildly while receiving oral steroids,
resolving completely when treated with oral anti-
biotics. Case #12 was the only one of four that was
also treated with a topical antibiotic (mupirocin), andthe only case where follow-up indicates recurrence of
lesions after cessation of topical antibiotic treatment.
Case #15 had recurrent bronchopneumonia that was
treated intermittently with oral and injectable antibiot-
ics for more than 1.5 years.
Therapeutic responsiveness could not be classified
for 2/17 dogs with follow-up. Case #16 was treated
with oral and topical antibiotics for greater than
1 month with only mild to moderate improvement;
immunomodulatory drugs were not administered.
Case #17 was treated with culture-based oral antibiotics
for 30 days with modest improvement, topical andoral steroids for greater than 1 month with no improve-
ment, and a combination of tetracycline and niacina-
mide for 3 months with no improvement.
Histopathological evaluationAll reviewers noted that there were cases with a
lymphocyte-rich interface dermatitis, with apoptosis and
vacuolar degeneration of the basal cells (LLDN) that
were easily distinguishable from other cases. Therefore,
each slide was subsequently assigned one of three pat-
terns. These patterns were not equivalent to a clinical
diagnosis or response to therapy:
1 Pattern L (LLDN): Presence of a lymphocyte-rich
interface dermatitis with apoptosis and vacuolar
degeneration of the basal cells (Fig. 1).
2 Pattern M (MCP-like): Presence of a band-like
diffuse superficial plasmacytic dermatitis with
minimal evidence of basal cell damage (Fig. 2).
3 Pattern M/L: A dermatitis demonstrating varying
degrees of features present in patterns L and pattern
M. The superficial dermal infiltrate was lympho-
plasmacytic, with focal evidence of basal cell damage.
A histopathological pattern was assigned to all cases
(17/27) that were available for follow-up (Table 1). All
authors reported only two cases with a lymphocyte-
rich interface dermatitis with apoptosis and vacuolar
degeneration of the basal cells (pattern L; Fig. 1).
However, authors’ opinions varied when assigning pat-
terns to some cases not definitively pattern L (Table 1;
Fig. 3). The 10/17 cases that were not available for
follow-up were then reviewed by all authors (data
not shown), and none of these cases were classified as
pattern L by any of the reviewers.
Numeric scores for predefined histopathological fea-
tures were recorded for all 27 cases (data not shown).
Comparing histopathological and clinical data
Pattern assessment vs. response to treatment. When
comparing response to treatment to the patterns
assigned, the two cases with pattern L (Table 1, cases
#10 and #11) responded to immunomodulatory treat-
ment. Neither of these cases had received antibiotics or
was on any treatment at the time of biopsy. One of
these cases (#11) had never received antibiotics and
demonstrated complete improvement on a long course
of oral prednisone, while the other case (#10) received
only 6 days of ampicillin, and demonstrated complete
response when placed on a combination of tetracycline
and niacinamide plus topical betamethasone. These
cases had a follow-up of 12 and 24 months, respectively.Of the 15 cases that were not definitively pattern L,
five cases were classified as pattern M in both reviews.
Of these five cases, three were immunomodulatory
Figure 1. Pattern L, case #10. Diffuse predominantly lymphocytic
infiltrate in the superficial dermis, obscuring the dermoepidermal
unction (H&E, ×10, bar = 50 µm).
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Comparing Canine DLE and MCP 345
responsive, and two were antibiotic responsive. One of
the fifteen cases was classified as pattern M/L in both
reviews, and was antibiotic responsive. The remaining9/15 cases were classified as pattern M by one reviewer,
and M/L by the other. Six of these nine cases were
immunomodulatory responsive, 1/9 was antibiotic
responsive, and therapeutic responsiveness (clinical
diagnosis) could not be assigned to 2/9 cases (#16 and
17) (Table 1).
Histopathological features vs. response to treatment.
There were no significant differences when scores for
each of the histopathological features were compared
between cases that were immunomodulatory respons-
ive or antibiotic responsive (Table 2). Therefore, noneof these individual features could predict the response
to therapy, and therefore could not help to distinguish
an autoimmune from an infectious process.
Duration of clinical signs and character of cellular
infiltrate. The mean duration (months) of clinical signs
before biopsy for all cases (6/27) with a ‘character of
cellular infiltrate’ score of 0 was found to be signi-
ficantly longer (mean: 28.5 ± 16.1 months) than the
mean duration for all cases (21/27) with an infiltrate
score of 1.5 or higher (mean: 13.5 ± 12.5 months;
P = 0.026). The two cases that responded to immuno-
modulatory treatment and which received a patternL were both assigned an infiltrate score of 3 (e.g. pre-
dominantly lymphocytic infiltrate), and had durations
of 12 and 36 months.
Table 1. Characterization of cases by response to therapy or
pattern type
Case #
Response
to therapy*
Review
(EAM, SPW)†
Review
(MHG)†
1 ImR M M/L
2 ImR M M
3 ImR M M/L4 ImR M M/L
5 ImR M M
6 ImR M M
7 ImR M M/L
8 ImR M/L M
9 ImR M/L M
10 ImR L L
11 ImR L L
12 AbR M M
13 AbR M M
14 AbR M M/L
15 AbR M/L M/L
16 – M M/L
17 – M/L M
*Cases were designated as immunomodulatory responsive (ImR) orantibiotic responsive (AbR).
†Pattern types were assigned ‘L’ (presence of a lymphocyte-rich
interface dermatitis with apoptosis and vacuolar degeneration of the
basal cells); ‘M’ (presence of a band-like diffuse superficial
plasmacytic dermatitis with minimal evidence of basal cell damage);
or ‘M/L’ (dermatitis demonstrating varying degrees of features
present in pattern M and pattern L. The superficial dermal infiltrate
was lymphoplasmacytic, with focal evidence of basal cell damage).
Figure 2. (a) Pattern M, case #13. Epidermal hyperplasia with a
diffuse plasmacytic superficial dermal infiltrate and marked
pigmentary incontinence, with mild vacuolar degeneration and
occasional apoptotic basal cells (H&E, ×10, bar = 50 µm). (b) Pattern
M, case #13. Higher magnification. Mild vacuolar degeneration
with central apoptotic keratinocyte (H&E, ×20, bar = 20 µm).
Figure 3. Depending on reviewer pattern M or M/L, case #3.
Epidermal hyperplasia with diffuse plasmacytic superficial dermalinfiltrate and mild multifocal vacuolar degeneration and occasional
apoptotic basal cells (H&E, ×10, bar = 50 µm).
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Original histopathological diagnosis assigned andresponse to treatmentThere was no correlation between the original his-
topathological diagnosis assigned to cases and the
clinical response to treatment.
DISCUSSION
For more than 20 years, the term ‘canine DLE’ has
been used to refer to a disease that presented with
varying degrees of erythema, crusting, erosions,
ulcerations, hypopigmentation, and loss of the ‘cobble-
stone’ architecture of the nasal planum. The lesions
may wax and wane and are often photosensitive.
Although the exact pathomechanism of the disease has
not been elucidated, it is thought to be an autoimmune
process.
There is the sense among some veterinary patholo-gists and dermatologists that some cases of nasal der-
matitis that behave clinically as ‘canine DLE’/LLDN
(e.g. controlled with immunomodulatory treatment)
cannot be readily distinguished by histopathology
from MCP. Indeed, in this study three cases that were
immunomodulatory responsive (cases #2,5,6) could
not be distinguished from two antibiotic-responsive
cases (#12 and 13) on the basis of histopathology
(e.g. all cases were assigned the same pattern (M) by re-
viewers). There were other cases that were all immuno-
modulatory responsive, but had different histopathological
patterns (e.g. patterns M, M/L, and L). Several hypo-theses have been proposed to explain why these cases
with the same response to therapy could demonstrate
different patterns (pattern L vs. patterns M and M/L):
(1) There may be more than one histopathological and
clinical pattern consistent with an autoimmune disease
of the nasal planum;11 (2) histopathological changes in
canine nasal dermatitis may occur along a continuum;
(3) plasma cells, resulting from secondary infection,
may complicate identification of lymphocytes (thus
shifting a pattern L to a pattern M or M/L); (4) mucous
membranes and mucocutaneous tissue will respond to
any form of injury that elicits a chronic inflammatory
cell response with a plasmacellular subepidermalinfiltrate.6 Therefore, any trauma (rubbing, licking,
scratching, etc.) to the nasal planum of a dog with LLDN
may result in a plasmacellular infiltrate admixed with
lymphocytes; recognition of the lymphocyte-rich pattern
in these cases would be difficult.
In this study, neither pattern assessment nor semi-
quantitative evaluation of key histopathological features
was successful in predicting response to treatment for
a majority of the cases. However, pattern recognition
was useful in distinguishing cases with plasmacytic
lymphoplasmacytic, band-like superficial dermatitis
(pattern M and M/L, respectively) from those cases
with a predominantly lymphocyte-rich interface der-
matitis (pattern L). When evaluating the histopathology
of each case blindly, all reviewing authors identified the
same two cases as having a lymphocyte-rich interface
dermatitis (pattern L). Although these two cases
responded to immunomodulatory therapy, more cases
are needed to confirm that all cases of pattern L would
be immunomodulatory responsive. The reviewing
authors’ assignment of pattern varied in some cases
that were not clearly pattern L, confirming that themost confusing cases for the dermatopathologist to
diagnose are those cases with a plasmacytic to lympho-
plasmacytic infiltrate and evidence of mild basal cell
damage. With the current understanding of histo-
pathology associated with these diseases, unless a case
has features that are clearly pattern L, a consistent pat-
tern and diagnosis cannot be assigned. Because cases
that were not classified as pattern L did not respond
uniformly to treatment (e.g. some were antibiotic res-
ponsive while others were immunomodulatory respons-
ive, and some did not respond to therapy), it is likely
that these cases (patterns M and M/L) representedboth infectious and autoimmune diseases.
The fact that a predominantly plasmacytic infiltrate
was significantly associated with duration is consistent
with known immunological mechanisms. This finding
must be considered when evaluating the character of a
particular infiltrate. Although a predominantly plas-
macytic infiltrate is suggestive of MCP, it could be
hypothesized that older, infected cases of LLDN would
appear similar. However, given that the two pattern L
cases in this study had a duration of 12 months and
36 months, and neither were treated with antibiotics
prior to biopsy, it is evident that not all chronic pattern
L cases will eventually become infected.German shepherd dogs and their crosses were over-
represented in cases of nasal dermatitis and tended
to have more multifocal lesions than other breeds.
Histopathological feature measured
P-values* when comparing means from
ImR cases (n = 11) to AbR cases (n = 4)
Character of infiltrate at dermoepidermal junction 0.332
Vacuolar degeneration 0.199
Apoptotic basal cells 0.136
Pigmentary incontinence 0.325
Lymphocytic excocytosis Not significant (chi-square)
Basement membrane thickening 0.50
Epidermal hyperplasia 0.73
Atrophy Not significant (chi-square)
*P-values derived from Mann–Whitney statistical test, except where otherwise noted.
Table 2. Statistical evaluation of mean
scores when histopathological features were
quantified from cases that were
immunomodulatory responsive (ImR) or
antibiotic responsive (AbR)
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Comparing Canine DLE and MCP 347
Interestingly, none of the German shepherd dogs or
crosses had a pattern L infiltrate.
There are several caveats to note with this study.
Because of the retrospective nature of the study, the
approach to therapy and measurement of improve-
ment on therapy was not standardized. Therefore,
when the terms ‘complete resolution’ or ‘completeresponse’ were reported, it is not clear if the nasal pla-
num appeared physically normal to the clinician, or if
the terms were used to indicate a dramatic improve-
ment of lesions and additional improvement was not
expected. In either case these terms were used to
describe the lesions and not whether the disease pro-
cess was cured or simply controlled by treatment. This
is especially important to note in cases that were cat-
egorized as ImR. A disease process that is responsive
to immunomodulatory therapy, and therefore likely
autoimmune, may be controlled, but not cured, with
long-term treatment. The amount of information
available from the records regarding follow-up varied
tremendously and may have affected evaluation of
each case’s response to treatment. A more complete
and specific clinical description with regard to sym-
metry, atrophy, degree of crust formation vs. presence of
scale and exact location on the nasal planum may have
added clinical information that could have been cor-
related to the histopathological patterns. The small
number of cases available for this study, particularly
those with sufficient follow-up to allow an assessment
of response to treatment, was also a limitation. Any
attempt to standardize histopathological evaluation is
limited by the reviewer’s skill and subjective nature of the measurement. This is compounded by the fact that
histopathological sections of nasal planum are not
uniformly affected in these disease processes.
The findings of this study show that in many cases of
nasal dermatitis, histopathological changes can not
predict response to treatment, and thereby distinguish
an autoimmune from an infectious process.
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Meeting, Nashville, Tennessee (April 1997), (Invited lec-
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the Beholder, an opinion.
11. Forget M, Degorce-Rubiales F, Bensignor E. Lupus
cutané chez le chien: étude rétrospective de 15 cas. Pra-
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Résumé Le lupus discoïde canin (DLE) et la pyodermite cutanéomuqueuse (MCP) ont des aspects cliniques et
histopathologiques communs, rendant le diagnostic difficile. Dans cette étude, 27 biopsies de la truffe ont été
étudiées pour déterminer si le DLE et la MCP étaient différenciables sur le plan histopathologique. Un suivi aulong cours, permettant un diagnostic clinique, était disponible dans 15 cas. 11/15 ont bien répondu à l’immuno-
modulation (ImR) et 4/15 aux antibiotiques (AbR). Le diagnostic clinique, déterminé par la réponse thérapeu-
tique pour 15/27 cas, n’a pas pu être prédit par l’aspect histopathologique. Des patrons histopathologiques dif-
férents ont été observés: 2/11 cas d’ImR avaient une dermatite d’interface riche en lymphocytes. Tous les autres
cas avaient un aspect histopathologique semblable: dermatite diffuse, en bande superficielle, plasmocytaire ou
lymphoplasmocytaire,± atteinte des cellules de la basale, mais des diagnostics cliniques différents (4/4 AbR, 9/
11 ImR). Les Berger allemand ou leurs croisés étaient sur-représentés (44.4% des cas) et avaient tendance à
présenter des lésions plus multifocales (41.7% versus 26.7% pour les autres races). Une durée plus longue d’évo-
lution était associée à une prédominance de plasmocytes dans l’infiltrat (P = 0.026).
Resumen El lupus discoide canino (DLE) y la pioderma mucocutánea (MCP) presentan cambios clínicos e histo-
patológicos comunes, dificultando a menudo el diagnóstico. Se estudiaron las características histopatológicas
de 27 biopsias de plano nasal para determinar si el DLE y la MCP eran distinguibles histopatológicamente. Se
pudo realizar un seguimiento a largo plazo, permitiendo valorar los diagnósticos clínicos en 15 casos; 11/15 casos
respondieron a terapia inmunomoduladora (ImR) y 4/15 respondieron a antibióticos (AbR). El diagnóstico
clínico, determinado por la terapia al tratamiento en 15/27 casos, no podía predecirse basándonos en la puntuación
de las características histopatológicas. Se observaron características histopatológicas definibles: 2/11 casos de
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348 SP Wiemelt et al.
© 2004 European Society of Veterinary Dermatology, Veterinary Dermatology, 15, 341–348
ImR tenían una dermatitis de la unión rica en linfocitos. Los demás casos mostraron las mismas alteraciones
histopatológicas, una dermatitis superficial en banda difusa plasmacítica a linfocítica ± daño focal de células
basales, pero con diferentes diagnósticos clínicos (4/4 AbR, 9/11 ImR). Los perros Pastor Alemán y sus cruces
se encontraban sobre-representados (44.4% de los casos) y tendían a tener más lesiones multifocales (41.7% ante
26.7% de todas las razas). Se asoció una mayor duración de la enfermedad con un predominio de infiltrado
linfocítico (P = 0.026).
Zusammenfassung Caniner diskoider Lupus erythematodes (DLE) und mukokutane Pyodermie (MCP) haben
sich überschneidende klinische und histopathologische Veränderungen, was die Diagnose oft schwierig macht.
Histopathologische Merkmale von 27 Biopsien vom Planum nasale wurden ausgewertet, um zu bestimmen, ob
DLE und MCP histopathologisch unterscheidbar sind. In 15 Fällen war ein Langzeit-Follow-up, das die
Bewertung der klinischen Diagnose ermöglichte, verfügbar; 11/15 Fälle reagierten auf immunmodulatorische
Therapie (ImR) und 4/15 auf Antibiotika-Therapie (AbR). Die klinische Diagnose, gestellt durch Therapieerfolg
bei 15/27 Fällen, war basierend auf Auswertung histopathologischer Veränderungen nicht voraussagbar. Unter-
schiedliche histopathologische Muster wurden beobachtet: 2/11 ImR Fälle zeigten eine Interface-Dermatitis, die
reich an Lymphozyten war. Alle anderen Fälle zeigten dieselben histopathologischen Veränderungen: eine
bandförmige diffuse superfizielle plasmazytäre bis lymphoplasmazytäre Dermatitis ± fokale Schädigung der
Basalzellen, aber unterschiedliche klinische Diagnosen (4/4 AbR, 9/11 ImR). Deutsche Schäferhunde und
Schäferhund-Mischlinge waren überpräsentiert (44,4% der Fälle) und tendierten zu mehr multifokalen Läsionen
(41,7% gegenüber 26,7% bei anderen Rassen). Längere Erkrankungsdauer war mit einem Vorherrschen eines
plasmazytären Infiltrates verbunden (P = 0.026).