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Commonly asked
questions about dermatomyositis
in dogs
(DM or FCD)
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Although this article is written mainly for
Collies and Shetland Sheepdogs it contains some information that
you may find useful
NOTE: Some people use the abbreviation
DM to stand for diabetes mellitus (a type of diabetes) or demodex (a
type of mite found on skin scraping). When we use this
abbreviation we are using
it to represent the skin disease dermatomyositis.
1. What is dermatomyositis?
Dermatomyositis (DM) is a devastating inherited inflammatory disease of
the skin and/or muscle which most commonly afflicts Collies, Shetland
Sheepdogs and their crosses. The skin lesions consist of hair loss with
or without skin
redness, scaling and crusting of the face, ears, legs and tail tip. One
or
more of these areas of the body may be affected. In addition, some dogs
may
have muscular involvement. Sometime this muscle involvement is so
pronounced
that it results in muscle atrophy. Other cases may suffer from
megaesophagus
(enlarged food tube in the body) with the end result of aspiration
pneumonia.
In milder cases the dogs may appear to be sloppy eaters, or have a
strange
high stepping gait. Shetland sheepdogs are fortunate because muscle
involvement
does not seem to be as common as with the Collie. Most commonly dogs
develop
the skin lesions within the first few years of life but dogs as old as
8
years old have been reported to develop this problem. It is thought
that
certain triggering factors such as stress may cause a dog to express
the
DM. These triggering factors are thought to include such circumstances
as
a bad viral infection (e.g. parvo) and hormonal fluctuations (heat
cycles). In some cases no triggering factor has been identified. Intact
females appear to be more subject to hormone related stresses than
intact males. Stress of
travel, moving, family upsets may also make the symptoms worse. Since
this
is a genetic problem, affected dogs should be spayed or neutered. This
will
also help the dogs respond better to treatment. DM is not an itchy
problem unless a secondary infection is present. So if your pet is
itchy and it does not look like a secondary infection is present
(bacteria or yeast) then your pet's problem is probably not DM. The
only exception would be if you had a
dog with DM and an underlying allergy. This can occur but is not common.
2) How is DM treated?
Steroids - Side effects include liver problems, suppression of
the adrenal gland function, and secondary infections due to the
immunosuppression.
Pentoxifylline - Side effects of pentoxifylline can be diarrhoea
and vomiting. These side effects have only been seen when the drug is
not
given with food, or a generic brand of pentoxifylline is used.
IT IS
IMPORTANT TO ONLY USE THE BRAND NAME TRENTAL®
if you decide to use
pentoxifylline as your treatment option. When generics have been used
they have been found to be either ineffective (not helped the animal
with the DM) or associated with side effects of vomiting and diarrhoea.
Azathioprine (Imuran" ) - Azathioprine is the most common type
of immunosuppressive drug that has been reported to be used to treat DM
in dogs. The use of this drug in dogs has been associated with several
different side effects. The main side effect that azathioprine causes
is bone marrow suppression (decreased red blood cell count, decreased
white blood cell count, decreased platelet count). Other side effects
of azathioprine in dogs include vomiting, diarrhoea (most common side
effect, may have blood in stool), hypersensitivity reactions
(especially the liver), an inflamed pancreas, skin rashes and hair
loss. These dogs need to be closely monitored by a vet and
periodic bloodwork performed on them (initially every 2 weeks) to make
sure that the dog is not having a problem with the azathioprine.
Immunostimulant drugs- Immunoregulin is a product of a kind of
killed bacteria (Propionibacterium acnes) which is injected in the vein
during set periods of time (initially twice weekly, then weekly then
monthly). Side effects occasionally occur after the injection and
include lethargy, increased body temperature, chills and decreased
appetite. Anaphylactic shock reactions have also been reported. If the
drug is given outside of the vein then local tissue inflammation
(swelling) has been reported. long term toxicity studies have
demonstrated inflammation of the liver (hepatitis), vomiting,
diarrhoea, decreased appetite, malaise (feeling poorly), fever,
increased water consumption and acidosis.
Antioxidants - The most common antioxidant which has been used
to treat DM is Vitamin E. Some have used it topically but most vets use
it systemically (give a tablet or capsule by mouth). If used at the
dose reported in the literature
then no side effects have been reported. This treatment has not been
evaluated
scientifically in a large number of dogs. Contact your vet for
recommendations
on the appropriate dose of Vitamin E to use on your dog.
3) How long will my DM dog need to be treated?
This is a grey area. We do not know for sure. Some dogs need 3 to 6
months of treatment and do fine whereas other dogs need life long
therapy. The length of treatment varies according to the individual dog
and the severity of the disease.
4) How is DM genetically expressed or passed on? We do not know
but we have seen this problem in certain breeding lines so we know that
it is an inherited problem. The exact mode of inheritance is not known.
This is the reason for the genetics study that is being performed at
Texas A&M College of Veterinary Medicine.
Does my dog have dermatomyositis?
This is the information that your vet needs to have in order to be able
to answer this question.
1) When should I biopsy? If you have a Shetland Sheepdog, Collie
or their cross with any of the clinical signs described in the first
paragraph then you should have your dog biopsied.
2) Where should I biopsy? Affected areas of the skin and/or
muscle are the locations where the biopsy should be taken.
3) How many biopsies should I take? A minimum of 3 biopsies
should be taken.
4) What size of biopsy sample should I take? The diameter of
each biopsy should be at least 6 mm in size. If you choose to use a
biopsy punch to take your sample then you will need to use scissors or
a scalpel to collect some of the muscle below your biopsy site.
Remember, the muscle may be involved with this disease so it is very
important to obtain muscle tissue along with your skin sample.
5) How should I store the biopsy samples? Each biopsy sample
should be placed in an individual container with 10% neutral buffered
formalin. The
owner's name, pet's name and date should be written on each container
with
a permanent marker.
6) Where should I submit my biopsy samples? Drs. Dunstan and
Credille are two of the leading veterinary dermatohistopathologists who
have a special interest in DM. They are both at Texas A&M
University.
7) Does the submission to Texas A&M require a special form?
The answer to this question is yes. This special submission form may be
obtained by calling Dr Christine Rees at the TX A&M Small Animal
Clinic (979-845-2351; CREES@cvm.tamu.edu) or by contacting Sherry
Lindsey RN BSN (830-620-6661), Shalainetx@aol.com). Samples should be
sent directly to:
Dr. Christine Rees
Texas A&M University
College of Veterinary Medicine
Department of Small Animal Medicine and Surgery
College Station, TX 77843-4474
You need to contact Dr. Rees by email prior to shipping the samples so
she will know biopsy samples are coming. The laboratory no longer
accepts submissions for DM diagnosis directly to the laboratory.
8) What other samples ore needed to study DM? Blood samples
(preferred) or cheek swabs for DNA material and 5-7 generation pedigree
information are needed from DM dogs.
9) What kind of blood samples are needed? (a) Frozen serum (1.5
mi minimum). Whole blood should be collected in a 5 ml red top
vacutainer tube, spun in a centrifuge, and the serum removed and
shipped cold in a polystyrene container. Each tube should be labelled
with permanent marker giving the owner's
name, the pet's name and the collection date. The samples should be
wrapped
in newspaper and packed with a frozen cold pack. Samples should be sent
overnight
delivery. (b) Whole blood in EDTA (2.5 mi minimum)- Whole blood should
be
collected in a lavender top vacutainer tube and kept cold but not
frozen
as described above. The owner's name, pet's name and collection should
be
clearly labeled on the tube using a permanent marker. Cheek swabs may
be
obtained from Dr. Rees at Texas A&M University College of
Veterinary Medicine.
10) What type of pedigree information is needed? Even if your
dog does not have DM, a 5-7 generation pedigree would provide valuable
information for our DM research. We need to know which dogs are normal
and which ones are abnormal in a pedigree so we can determine the
possible mode of inheritance for DM.
11) What is the charge? We will perform the DNA and pedigree
analysis at no charge. We will charge the usual rate for the
interpretation of the biopsy sample which is $50.
Questions? Contact Dr. Christine Rees in the Dermatology
Department at Texas A&M University. Phone (979) 845-2351 or FAX
(979) 845-6978 or email:crees@cvm.tamu.edu . She is actively involved
in projects dealing with the treatment of DM. Sherry Lindsey RN,
BSN at (830) 620-6661 or email: Shalainetx@aol.com. Sherry is a breeder
working with Dr.
Rees in the DM studies at Texas A&M.
The above information is simply informational. It's intent is
not to replace the advice of a veterinarian nor to assist you in making
a diagnosis of your pet. Please consult with your own veterinarian for
confirmation of any diagnosis. Your pets life may depend on it.