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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.