Diseases of the planum nasale - Veterinary Practice
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InFocus

Diseases of the planum nasale

Dr SUE PATERSON reviews the range of dermatological diseases which affect the nasal planum

THE planum nasale is affected in a
whole range of different
dermatological diseases. In fact,
flicking through almost any
dermatology text book
you will find a disease in every chapter that affects the nasal planum. In some cases the disease only affects the nose, in others it is part of a much more generalised pattern.

A working
knowledge of the types
of diseases that affect
the area is useful but
even when disease
presents with classical
signs in a predisposed
breed it should not stop the clinician
from undertaking a thorough
dermatological work-up.

Diseases can be divided by both
aetiology and also by presenting signs.
The latter is the most useful
classification because it enables the
clinician to develop a logical approach
to diagnosis.

Broadly, the diseases can be
categorised as ulcerative, nodular,
papular and pustular; crusting and
scaling and depigmenting diseases. The
clinical presentation can help decide
which diagnostic tests are most
appropriate. Exudative lesions such as
ulcers, papules and pustules lend
themselves to impression smears. Where
infection is present, Diff Quik stains of
the exudates can help provide
information. Pustule cytology can also
help differentiate between sterile and
pustular diseases.

Dermatophyte culture

In cases of pemphigus foliaceus,
bacteria are not usually seen, neutrophils
appear non degenerate and acanthocytes
are present. Where areas of alopecia
with scale are present, which can be
seen with some of the immune-
mediated diseases as well as demodicosis
and dermatophytosis, then hair plucks,
skin scrapes and dermatophyte culture
should be performed.

Fine needle aspirates are essential
for nodular lesions. In such diseases as
sterile eosinophilic furunculosis or
sterile pyogranulomatous disease,
aspirates can differentiate inflammatory and hyperplastic disease from neoplastic
disease such as mast cell tumours.

Where initial diagnostic tests are
unrewarding, then biopsy and tissue culture are usually
indicated. Care should
be taken when
biopsies are performed
to include epidermis
within the sample. In
ulcerative disease, the
epidermis is lost which
means biopsies taken
from the centre of
lesions can often
provide no useful
diagnostic information.

Auto-immune and
immune-mediated skin
diseases are often
ulcerative and produce some of the most
dramatic clinical pictures. Discoid lupus erythematosus and pemphigus
erythematosus which are sunlight-
induced diseases are typically seen in
such breeds as the rough collie and
German Shepherd dog.

The disease process which targets
antigen deep in the skin produces severe
erosion and ulceration of the planum
nasale during the summer months,
which can lead to long-term damage to
the nasal skin. Proliferative nasal arteritis
has to date only been described in the St
Bernard. Dogs tend to have deep-seated
punched-out ulcers on their nasal
planum.

Difficult to manage

Haemorrhage due to immune-mediated
vessel damage is a common sequel with
this disease which makes management
difficult. Vasculitis commonly affects the
nose and the Scottish terrier has been
identified as a breed predisposed to
developing vasculitis affecting the nasal
planum. It can present with ulcers
similar to nasal arteritis.

The most important metabolic
disease to affect the nasal skin is
necrolytic migratory erythema. Lesions
of this disease form the cutaneous
manifestation of much more serious
internal problems including pancreatic
or hepatic neoplasia.

Pemphigus foliaceus (PF) can also
affect the planum nasale. In PF the
inflammatory reaction is directed at much more superficial antigen in the
epidermis so lesions tend to be pustular
and crusted rather than ulcerative. With
the exception of the Akita, PF is not
induced by sunlight and generally dogs
have involvement of other areas. Often
they have more generalised pustular
disease and 90% of dogs have footpad
hyperkeratosis.

In the Akita, PF is principally seen in the warm summer months and
uniquely in the Akita it is not
uncommon for it only to affect the
nasal skin with few or no signs at other
sites.

Some of the infectious diseases can
mimic auto-immune diseases in their
clinical presentation. Mucocutaneous
pyoderma is one of the major
differentials for DLE and can occur
concurrently, making a definitive
diagnosis difficult. In such cases
aggressive antibiotic therapy based on
culture and sensitivity should be
undertaken before biopsy is considered.

Trichophyton mentagrophytes, the rodent
ringworm, can also mimic auto-immune disease. It commonly appears as an
inflammatory disease with marked
erythema, together with exudation and
ulceration. Subtle differences can be
recognised in the distribution of
Trichophyton infection compared to
auto-immune skin problems:
Trichophyton lesions tend to be well
circumscribed and only affect the haired
skin, which means infection produces a
sharp cut-off point between the haired
and non-haired areas on the nose; auto-
immune disease affects both sites.

Although any breed can contract
Trichophyton infection, Jack Russell
terriers are highly predisposed due to
their life-style involving close contacts with rodents.
Allergic reactions that affect the nose can also
appear as inflamed
erythematous lesions.
Contact allergy caused by
reactions to feeding bowls
is typically seen on the
nose. Although dogs with
both food allergy and
atopic dermatitis have
facial pruritus, it is unusual
to see lesions confined to
the nasal planum in either
disease.

White-haired animals
are more prone to
sunlight-induced disease.

The earliest lesions appear
as actinic dermatitis where
there is mild erythema and
scaling. Continued sunlight
exposure can lead to the
development of overt
neoplasia in the form of
squamous cell carcinoma.
Other diseases that can
present with degrees of
scale and crusting include
immune-mediated problems
such as exfoliative
cutaneous lupus
erythematosus of the
German short-haired
pointer and infectious
diseases such as leishmaniasis and
distemper.

Naso-digital hyperkeratosis can be
seen as an idiopathic disease in older
animals. It can be difficult to control
and requires emollient to prevent
cracking of the nasal skin. When clinical
signs occur in specific breeds, their
predisposition to certain conditions can
offer clues as to the underlying
aetiology.

Zinc deficiency

The Arctic breeds such as the Siberian
Husky and Alaskan Malamute
commonly suffer from zinc deficiency.
Although lesions will affect other sites
including the feet and pressure points, hyperkeratosis of the nasal planum can
be seen.

Hereditary nasal parakeratosis is an
unusual disease commonly seen in
young Labradors between the ages of
six and 12months. The nasal planum
becomes dry and cracked. Therapy can
be difficult.

Pigment loss in the nasal skin is
often a completely benign presenting
sign which causes more distress to
owners than it does to the dogs. Vitiligo
and snow nose are common examples
of this. Vitiligo is seen most commonly
in breeds such as the Rottweiler and
Dobermann where pigment in such
areas as the nasal planum, lips and peri-
ocular skin is destroyed by auto-immune attack against epidermal melanocytes.
Snow nose is a tardive onset

hypopigmentation of the nasal
planum seen in such breeds as the
yellow Labrador. In such breeds as
the Akita, depigmentation can be part
of a much more sinister syndrome
called Vogt Koyanagi Harada-like
syndrome (VKH). This is an immune-
mediated attack against melanocytes.

Concurrent uveitis

Depigmenting lesions often affect the
peri-ocular skin; however, many dogs
develop concurrent uveitis which has
the potential to cause blindness. In
older dogs, depigmentation of the
planum nasale often heralds the
development of epitheliotropic
lymphoma.

Neoplastic lymphocytes damage pigment cells in the stratum basale
leading to a blue-grey discolouration
of the nasal planum.

Sterile eosinophlic furunculosis is
another very florid nodular disease
which has a peracute onset. Young,
active gundog types are predisposed to this problem which is thought to
be associated with the bites of
venomous insects.

Dogs frequently present after a
period foraging about in
undergrowth.

What appears on initial
presentation to be a small innocuous wound quickly develops into extensive
nodular exudative lesions that extend
up the whole of the nasal planum.
Other nodular diseases that can affect
this site include histiocytosis, sterile
pyogranulomatous disease and
neoplastic disease, especially mast cell
tumours.

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