Inherited immune disorders

Canine cyclic hematopoiesis

roblib — Thu, 18 Mar 2010 14:37:04 +0000

What is ... ?:

This disorder of the immune system occurs in gray collies. Puppies are usually smaller and weaker than their littermates and by 8 to 12 weeks of age they develop clinical signs such as fever, diarrhea or joint pain, or other signs associated with eye, respiratory, or skin infections.

The disorder is caused by an abnormality of the stem cells in the bone marrow, from which all blood cells develop. The result is a cyclic fluctuation in blood cell numbers, primarily neutrophils, which are very important in fighting infections. Every 10 to 12 days, the number of neutrophils drops dramatically, and then rebounds. There is increased susceptibility to infection corresponding to the dip in neutrophil numbers. As well, the normal activity of the neutrophils is impaired. These dogs are also prone to bleeding episodes due to the drop in platelet numbers.

How is ... inherited?:

The mode of inheritance is autosomal recessive. Both parents must carry the abnormal gene for the offspring to be affected.

What breeds are affected by ... ?:

Collie (rough and smooth)

What does ... mean to your dog & you?:

This is a very serious disorder. These dogs are subject to severe recurring bacterial infections, primarily of the respiratory or gastrointestinal tract. Even with the best of care, affected dogs rarely live beyond 2 or 3 years of age.

How is ... diagnosed?:

Affected dogs have a light silver gray, possibly mixed with light beige, hair coat and a characteristic light coloured nose. Pups usually experience clinical illness by 8 to 12 weeks of age and are brought to the veterinarian at that time, if the breeder does not recognize the defect before then.

The disorder is diagnosed based on the cyclic fluctuation in blood cell numbers, as well as the characteristic coat coloration.

For the veterinarian:
Cyclic neutropenia occurs every 10 to 12 days, persists 2 to 4 days, and is followed by a rebound neutrophilia (during which infections resolve). Other hematologic abnormalities include non-regenerative anemia, and cyclic reticulocytosis, monocytosis, and thrombocytosis. Even with optimal care, affected animals usually die before 2 to 3 years of age due to chronic recurring infections and/or hepatic or renal failure associated with amyloidosis.

How is ... treated?:

The only practical treatment is supportive care and antibiotics during neutropenic episodes. Without supportive care, pups usually die before 6 months of age. Even with the best of care, including very close monitoring and antibiotics to counteract the variety of infections, these dogs usually die before 2 or 3 years of age.
Bone marrow transplant and gene therapy have been attempted on an experimental basis.
FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Breeding advice:

As a rule, parents and littermates of affected dogs should not be used for breeding, to avoid perpetuating this lethal defect.
HealthGene Laboratory offers a DNA-based test for canine cyclic hematopoiesis that identifies normals, carriers (heterozygous), and affected dogs, which will assist with judicious breeding.

Resources:

Raskin R. Hematologic disorders – cyclic hematopoiesis. In: Schaer M, ed. Clinical Medicine of the Dog and Cat. London, UK: Manson, 2010:261.
Sargan DR. Cyclic hematopoiesis in IDID - Inherited diseases in dogs:web-based information for canine inherited disease genetics. Mamm Genome. 2004 Jun;15(6):503-6.

Immune-mediated thrombocytopenia

roblib — Mon, 22 Mar 2010 17:07:43 +0000

What is ... ?:

Thrombocytopenia means a reduction in platelets (thrombocytes). Platelets (one of the cell types in the blood) play an important role in the clotting process; thus the main result of a decrease in platelets is increased bleeding - for example, nosebleeds.

In immune-mediated thrombocytopenia (IMT), the reduction happens because there is increased destruction of platelets by the body's own immune system, at a rate faster than they are produced in the bone marrow. IMT may be secondary to some other process (such as an infection, tumour, or drug reaction) or it may be primary, meaning that no other causative factor can be found. It is more common in certain breeds, suggesting an inherited genetic susceptibility. IMT may occur by itself or with other conditions like systemic lupus erythematosus and immune-mediated hemolytic anemia.

How is ... inherited?:

unknown. It is more common in female dogs than in males.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

The main problem for dogs affected by IMT is increased bleeding. Your dog may have nosebleeds, bruising on the gums or skin, and/or blood in the stool or urine (seen as a darker than normal colour). Your dog may also appear weak or lethargic.

Many dogs with IMT experience only one episode of thrombocytopenia, and respond well to treatment. Some dogs will have occasional relapses, which may be associated with stressors such as another illness, or travel. Unfortunately some dogs with this disorder die acutely because of severe internal bleeding.

How is ... diagnosed?:

With signs of increased bleeding, your veterinarian will do a CBC (complete blood count), which will show a dramatic drop in platelet numbers. Bleeding does not occur until the platelet count is below 25,000/µl of blood. (Normal levels are above 200,000).

Then it is a matter of ruling out other possible causes of thrombocytopenia, which are many. Any disorder that causes increased widespread excessive bleeding will cause a drop in platelets, simply because they are being used up (consumptive coagulopathy).

How is ... treated?:

Corticosteroids are given to slow platelet destruction, initially at high doses which are gradually tapered as platelet levels stabilize and begin to rise again. The response to treatment is usually good. If platelet levels continue to fall despite steroid therapy, other immunosuppressive drugs can be given.Blood or platelet-rich plasma transfusions may be required, to supply oxygen to the tissues and to control bleeding.

Aftyer recovery, ongoing monitoring is needed to identify any relapse early, and stressful circumstances should be avoided where possible.

For the veterinarian:

CBC (with manual differential) will usually be normal unless bleeding causes anemia. A peripheral blood smear should be evaluated for platelet clumping, size and morphology. Coagulation profiles (also usually normal with ITP) should be done to rule out intrinsic and extrinsic coagulation defects that may be causing a general consumption of peripheral platelets. Other differentials for thrombocytopenia include reduced production secondary to lymphoma, myeloproliferative disease, and preleukemic states. Bone marrow cytology is usually not necessary unless there are other abormalities; increased numbers and immaturity of megakaryocytes indicate a regenerative response, in contrast to an unresponsive or preregenerative bone marrow. Regeneration should be evident within 3 to 5 days of an acute thrombocytopenic episode.

The diagnosis of primary IMT is made if no causes of secondary IMT can be found, which is most often the case. Secondary IMT may be caused by certain drugs (cephalosporins, gold compounds and others), neoplasia, infectious diseases (eg. canine distemper), or other immune-mediated disorders such as SLE or IMHA.

Breeding advice:

Dogs that have had an episode of immune-mediated thrombocytopenia should not be used for breeding.

FOR MORE INFORMATION, PLEASE SEE YOUR VETERINARIAN.

Resources:

Neel JA, Birkenheuer AJ, Grindem CB. Thrombocytopenia. In: Bonagura JD, Twedt DC, eds. Kirk's Current Veterinary Therapy XIV. Missouri: Saunders Elsevier, 2009:281-287.
Stone M. Immune-mediated thrombocytopenia. In: Côté E, ed. Clinical Veterinary Advisor Dogs and Cats. Missouri: Mosby Elsevier, 2007:1079-1080.
Sargan DR. Thrombocytopenia. In IDID - Inherited diseases in dogs:web-based information for canine inherited disease genetics.

Atopy

roblib — Fri, 16 Apr 2010 18:37:23 +0000

What is ... ?:

Atopy can be considered the canine equivalent of hay fever. It is quite common, affecting around 10 per cent of dogs. Animals with this condition become sensitized to substances (allergens) in the environment, that are inhaled or absorbed through the skin (and which cause no problems for non-atopic animals). The resultant allergic reaction is primarily seen as extreme itchiness (pruritis).

The main allergens involved are house dust mites, house dust, human dander, feathers, molds, and pollens from trees, weeds, and grasses. Atopic dogs are also prone to seborrhea, secondary bacterial skin infections (pyoderma) and probably yeast (Malassezia) infections as well

How is ... inherited?:

The exact mode of inheritance is unknown. There is a strong breed predilection for this condition, and marked familial involvement (ie. if both parents are allergic, there is a very strong likelihood the offspring will be as well).

What does ... mean to your dog & you?:

The condition is usually first seen between 1 and 3 years of age, although it may develop as late as 6 or 7. Initially atopy may be seasonal (eg. from spring to fall) but most affected dogs eventually have signs all year round.

Dogs with atopy are very itchy. The areas most affected are the face, paws, lower legs, groin, and, less often, the ears and eyes. In addition to scratching themselves with their hind feet, they often lick or chew the affected areas, or rub along the carpet to scratch the face or ears. The intense itching can make them irritable and less tolerant of being handled.
Initially, there are no apparent skin abnormalities, except possibly slight reddening, even though the dog is clearly itchy. (This is important because in other conditions there is often a rash or some visible lesion.) Over time, lesions develop as a result of the scratching and self-trauma, bacterial or yeast infections, and seborrhea, all of which can contribute to the objectionable odor of these dogs. The skin becomes reddened and eventually darkened (hyperpigmentation), abraded, thickened, and wrinkled, with loss of hair and bronze staining from saliva.
The concept of "allergen load" is important in understanding and treating this disorder. Atopic dogs are generally allergic to more than 1 agent. A small amount of allergens may be tolerated without developing a reaction, but an increase in any one of those (ie. an increase in allergen load such as occurs during pollen season) may push your dog over the edge to an allergic reaction of extreme discomfort.

How is ... diagnosed?:

There are many skin diseases that cause itching, and they can all look rather similar on physical examination. Your veterinarian will ask you questions about your dog's diet, environment, any kind of skin care you are already providing, whether any other pets or people in the house are itchy, where and how quickly did the skin lesions start, and is there any seasonal pattern to the itching. The answers, as well as the age and breed of your dog, will provide diagnostic clues. For example, itching that begins suddenly and rapidly gets worse, is more typical of a flea allergy, scabies, or a drug hypersensitivity. Itching that begins insidiously and gradually worsens, is seen more often with atopy, food allergy, bacterial or yeast skin infection, and seborrhea. Skin infections and seborrhea commonly develop secondary to atopy and may have to be cleared up before your veterinarian can diagnose atopy.

Diagnostic tests may include multiple skin scrapings and smears (for mites or yeast infection), fecal examination (for parasites), skin biopsy, skin testing (for allergies to different substances), elimination diets or change in environment (if food or contact allergy is suspected),

How is ... treated?:

Atopy can be satisfactorily controlled in at least 90 percent of affected dogs. There are 3 components to successful treatment, which will be life-long and will likely require modification from time to time. A combination approach is generally most effective.

1 reduction in exposure to allergens. This requires identification of the substances to which your dog is sensitive (ie. allergy testing). You may be able to avoid some allergens altogether (if your dog is allergic to feathers or tobacco smoke for example), and reduce exposure to others (by keeping your pet out of carpeted areas to reduce house dust mite exposure for example). Your veterinarian will discuss this with you, in conjunction with the results of your dog's allergy testing.
2 hyposensitization (immunotherapy or "allergy shots"). This is recommended when the allergens involved can't be avoided, and your dog has clinical signs more than 4 to 6 months of the year which can not be kept under control with medical therapy. Immunotherapy is carried out after your dog's allergens have been identified by allergy testing. Injections of low doses of the appropriate allergens are given at short intervals at first, and then boosters given as needed when clinical signs begin to reappear.
3 medical treatment. Long term management may include gentle moisturizing anti-pruritic (control itching) shampoos, fatty acids, antihistamines (more likely effective when given as preventative), and short-acting corticosteroids on alternate days (given for short periods at times when there are flare-ups, to mimimize the potentially serious side-effects).

For the veterinarian:

A tentative diagnosis can be made based on history, physical exam, and laboratory tests to rule out other possibilities. Intradermal testing (and to a lesser extent, serologic allergy testing) is necessary for definitive diagnosis and identification of allergens involved. Diagnosis should not be made based solely on intradermal (because of low specificity) or serologic testing (very common false-positive reactions).

Intradermal testing is the preferred method of diagnosing canine atopy and determining appropriate immunotherapy. However to get good results requires experience, practice, and close attention to detail. Many factors can lead to false-positive and false-negative reactions. Where possible, it is desirable to refer cases to specialists in this area.

Breeding advice:

Although the specific mode of inheritance is unknown, it is best not to breed affected dogs, their parents, and preferably their siblings as well, given the strong familial predisposition to this condition.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Scott, D.W., Miller, W.H., Griffin, C.E. 1995. Immunologic Skin Diseases. In Muller and Kirk's Small Animal Dermatology. p. 500-518. W.B. Saunders Co., Toronto. This reference contains detailed information on allergy testing and on hyposensitization. Page 515 has practical suggestions for environmental management in atopic dogs.

Ihrke, P.J. 1995. Pruritis. In E.J. Ettinger and E.C. Feldman (eds.). Textbook of Veterinary Internal Medicine, pp. 214-219. W.B. Saunders Co., Toronto.

Bullous pemphigoid

roblib — Fri, 16 Apr 2010 18:52:33 +0000

What is ... ?:

This rare condition is an autoimmune disorder, meaning an abnormal immune response to a normal component of the body - in this case a protein in the skin. This results in blisters and ulcers in the skin and/or mouth. The disease is often severe, depending on how widespread are the affected areas.

This condition is very similar to bullous pemphigoid in people.

How is ... inherited?:

Inheritance is unknown.

What breeds are affected by ... ?:

Collie (rough and smooth)

What does ... mean to your dog & you?:

The blisters that occur with this condition are very short-lived, so you and your veterinarian are more likely to see ulcers. These lesions are found in the mouth and skin, particularly in the underarm and groin area. There may also be ulcerated areas around the nails or footpads. Your dog's skin may be itchy or painful, and it is common to develop a secondary bacterial infection (pyoderma). Dogs that are severely affected may lose their appetites, run a fever, or become depressed.

How is ... diagnosed?:

Your veterinarian will diagnose this condition based on physical examination of your dog, the history you provide, a skin biopsy, and immune testing. Other autoimmune or ulcerative skin disorders must be ruled out.

How is ... treated?:

Mild cases can be treated with steroid creams or relatively low doses of glucocorticoids by mouth. More severe cases usually require a combination of medications, including high doses of glucocorticoids, to suppress the inappropriate immune response. These drugs usually must be given for prolonged periods, possibly for life. Your veterinarian will discuss with you potentially serious side effects of which you should be aware.

Because exposure to ultraviolet light can make the condition worse, it is wise to keep your dog out of direct sunlight from 10:00 to 3:00.

For the veterinarian:

Cases with severe, widespread lesions are clinically indistinguishable from pemphigus vulgaris. Intact vesicles or bullae are suggestive of bullous pemphigoid.

Breeding advice:

Although the inheritance of this condition is unknown, it is preferable not to breed affected dogs.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Scott, D.W., Miller, W.H., Griffin, C.E. 1995. Immunologic Skin Diseases. In Muller and Kirk's Small Animal Dermatology. pp. 500-518. W.B. Saunders Co., Toronto.

Complement deficiency

roblib — Fri, 16 Apr 2010 19:43:19 +0000

What is ... ?:

Complement is a system of linked proteins that are an important part of the immune system. C3 is deficient in dogs with complement deficiency, and the result is an increased susceptibility to bacterial infections, and immune-related kidney disease.

How is ... inherited?:

This is an autosomal recessive trait. Dogs that are homozygous for the trait have no detectable C3, while heterozygous dogs have serum C3 concentrations approximately 30 to 50% of normal. Only homozygous dogs are clinically affected, but heterozygotes (carriers) can pass on the trait to their offspring.

What breeds are affected by ... ?:

Brittany

What does ... mean to your dog & you?:

From a young age, affected dogs are more likely to be infected by bacterial infections, including serious and widespread ones (septicemia). They may also develop kidney disease.

How is ... diagnosed?:

This disorder is rare. Your veterinarian may begin to suspect an immune deficiency when your pup has recurring bacterial infections. The diagnosis of complement deficiency is made based on a blood test showing little detectable C3.

How is ... treated?:

Antibiotics are used as needed to treat the infections. There is no treatment for the condition itself.

For the veterinarian:

Dogs that are homozygous have less than 10% normal serum C3. Heterozygotes have 30 to 50% normal levels.

Besides recurrent bacterial infections, affected dogs are prone to renal amyloidosis or membranoproliferative glomerulonephritis, relating to immune complex deposition.

Breeding advice:

Affected animals and their parents should not be bred. Any family members to be used for breeding should have blood tests to determine that they have normal serum C3 levels (in other words, that they are not carriers of the trait, in which case they should not be used for breeding).

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Ackerman, L. 1999. The Genetic Connection: A Guide to Health Problems in Purebred Dogs. p. 94. AAHA Press, Lakewood, Colorado.

Cyclic hematopoiesis

roblib — Mon, 19 Apr 2010 17:32:01 +0000

What is ... ?:

The disorder is caused by an abnormality of the stem cells in the bone marrow, from which all blood cells develop. The result is a cyclic fluctuation in blood cell numbers. Every 10 to 12 days, the number of neutrophils drops dramatically, and then rebounds. There is increased susceptibility to infection corresponding to the dip in neutrophil numbers. As well, the normal activity of the neutrophils is impaired. These dogs are also prone to bleeding episodes due to the drop in platelet numbers.

How is ... inherited?:

The mode of inheritance is autosomal recessive. Both parents must carry the abnormal gene for the offspring to be affected.

What breeds are affected by ... ?:

Pomeranian

What does ... mean to your dog & you?:

This is a serious disorder. These dogs are subject to severe recurring bacterial infections, primarily of the respiratory or gastrointestinal tract. Even with the best of care, affected dogs rarely live beyond 2 or 3 years of age.

How is ... diagnosed?:

The disorder is diagnosed based on the cyclic fluctuation in blood cell numbers, as well as the characteristic coat coloration.

How is ... treated?:

Other than bone marrow transplantation, which is impractical, there is no effective treatment. Without supportive care, pups usually die before 6 months of age. Even with the best of care, including very close monitoring and antibiotics to counteract the variety of infections, these dogs usually die before 2 or 3 years of age.

For the veterinarian:

Cyclic neutropenia occurs every 10 to 12 days, persists 2 to 4 days, and is followed by a rebound neutrophilia (during which infections resolve). Other hematologic abnormalities include non-regenerative anemia, and cyclic reticulocytosis, monocytosis, and thrombocytosis. Even with optimal care, affected animals usually die before 2 to 3 years of age due to hepatic or renal failure associated with amyloidosis.

Breeding advice:

Parents and littermates of affected dogs should not be used for breeding, to avoid perpetuating this lethal defect.

Resources:

Felsburg, P.J. 1992. Primary immunodeficiencys. In R.W. Kirk and J.D. Bonagura (eds), Current Veterinary Therapy XI Small Animal Practice, p.448-453. WB Saunders Co., Toronto. This has information on primary immunodeficiencies, including general information on management of animals with immunodeficiency diseases

German shepherd pyoderma

roblib — Mon, 19 Apr 2010 18:03:28 +0000

What is ... ?:

Bacterial skin infection (pyoderma) is very common in dogs, and is usually easily treated with antibiotics. Infection is almost invariably caused by Staphylococcus intermedius, which does not produce any problems in people.

Chronic, recurring, or deep infections can also occur, generally due to an underlying cause, and these are more difficult to treat. In German shepherds, a deep pyoderma is seen (meaning the infection extends beyond and beneath superficial structures in the skin) which causes severe chronic draining lesions in the area of the lower back and hind legs. Sometimes an underlying cause can be identified.

How is ... inherited?:

The predisposition to this condition is thought to be autosomal recessive; however as with all pyodermas, there are frequently other factors involved.

What breeds are affected by ... ?:

German shepherd

What does ... mean to your dog & you?:

The condition most often develops in middle-aged, otherwise healthy dogs. You may first notice that your dog bites at the lower back region, indicating itchiness. Early lesions such as pustules, erosions and crusting may be hidden by the haircoat but gradually there will be hair loss, deeper ulcerations and draining sinuses. The areas affected (lower back, outer thighs) may be quite painful.

How is ... diagnosed?:

The condition is diagnosed based on the clinical signs, response to antibiotics, and recurring nature.

How is ... treated?:

Predisposing factors such as fleas, flea-bite hypersensitivity, food allergies, and hypothyroidism must be identified and treated. Appropriate antibiotics must be given for a sufficient length of time, which may be as long as 6 to 10 weeks. Your veterinarian will likely also recommend antibacterial shampoos to remove infectious debris (discharge, crusts, etc).

This recurrent condition usually requires life-long management. Your veterinarian will work with you to devise a control programme that works for your dog, which may include immunomodulatory bacterins, long term antibiotic use, and/or regular antibacterial shampoos.

Breeding advice:

Avoid breeding affected dogs and their close relatives.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

DeBoer, D.J. 1995. Management of chronic and recurrent pyoderma in the dog. In J.D. Bonagura and R.W. Kirk (eds.) Kirk's Current Veterinary Therapy XII Small Animal Practice. p. 611-617. W.B. Saunders Co., Toronto.

Lupus erythematosus (systemic, cutaneous/discoid)

roblib — Mon, 19 Apr 2010 18:57:39 +0000

What is ... ?:

There are several forms of lupus erythematosus that are recognized in people, two of which have been identified in dogs. Lupus is an autoimmune disorder, meaning that the body mounts an inappropriate immune response to some part of itself.

Systemic lupus erythematosus (SLE) is an uncommon but severe disorder in which the inappropriate immune response is widespread in the body, and can cause arthritis, kidney disease, anemia, and skin disease. Cutaneous lupus erythematosus (CLE) is thought to be a milder variant of SLE, and the problems are confined to the skin. CLE is also called discoid lupus erythematosus

How is ... inherited?:

unknown, but the condition runs in families.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

SLE most commonly affects joints, muscle, skin, blood, and/or kidneys. The condition tends to wax and wane, so your dog will have periods of remission and of flare-up. The kinds of problems you may notice include shifting lameness (ie varies depending on which joint is affected at any time), weakness and pale gums (due to anemia), and/or increased drinking and urination (kidney disease). The face and the feet are the areas of the skin most often affected, with ulcers and loss of pigment on the nose, and ulceration and thickening of the footpads.

With CLE, you are most likely to see red, scaling areas of inflammation on your dog's face, and loss of pigment from the nose. There may also be lesions on the ears and thickening of the footpads. Affected dogs are otherwise healthy.
Nasal scarring is common with both SLE and CLE. Exposure to ultraviolet light is a factor (especially in CLE), and so the condition is seen more often and is more severe in the summer and in sunny parts of the world.

How is ... diagnosed?:

Because SLE can affect many different body systems, diagnosis is challenging. (In fact it is sometimes called, "the great imitator"). Once suspected, diagnosis is confirmed by specific blood tests and biopsy for examination by a veterinary pathologist.

CLE is diagnosed through examination of biopsy samples.

How is ... treated?:

Treatment for SLE generally requires relatively high doses of steroids in combination with chemotherapy. In general, dogs with joint, muscle, or skin disease seem to respond better to medication, and have longer periods of remission, than those with severe blood or kidney problems. Unfortunately, many dogs with SLE die or are euthanized within a year of diagnosis, either due to the disease itself, the inability to control it, and/or unacceptable drug reactions. In other dogs, the disease can be well-controlled with medication for several years.

CLE is treated with relatively lower doses of steroids plus vitamin E and fatty acid supplements. Treatment generally needs to be lifelong, and dogs usually do well on it.
Exposure to ultraviolet radiation worsens the skin lesions in both conditions, so sunscreen is adviseable and dogs should be sheltered from peak sunlight (approximately 10:00 to 3:00).
For the veterinarian: Treatment for SLE must be individualized for each dog, generally starting with large doses of systemic glucocorticoids, and going to other immunomodulating or chemotherapeutic drugs if necessary. There is a good discussion of treatments for both forms of lupus erythematosus in the reference below.

For the veterinarian:

The list of rule-outs with SLE is extensive, due to the varied and changeable cutaneous and systemic manifestations of this disorder. Diagnosis is based on signs of multisystem involvement (most commonly anemia, thrombocytopenia, glomerulonephritis, polyarthritis, nasal and footpad dermatitis, fever of undetermined origin), a positive antinuclear antibody test, and histopathologic and immunopathologic evaluation.

Diagnosis of CLE is by histopathologic and immunopathologic evaluation.

Breeding advice:

Although the mode of inheritance is not known for either cutaneous or systemic lupus erythematosus, these conditions run in families. Affected animals should not be bred and it is prudent to avoid breeding their close relatives as well.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Scott, D.W., Miller, W.H., Griffin, C.E. 1995. Immunologic Skin Diseases. In Muller and Kirk's Small Animal Dermatology. p. 578-588. W.B. Saunders Co., Toronto.

Pemphigus

roblib — Tue, 20 Apr 2010 17:20:23 +0000

What is ... ?:

Pemphigus covers a group of uncommon disorders that occur in dogs. With these conditions, there is an abnormal immune response to normal components of the skin, resulting in separation of cells. This leads to blisters, pustules, and crusting erosions in the skin. There are some similarities to pemphigus in humans, but many significant differences as well.

Breed predispositions are recognized for 2 forms - pemphigus foliaceus and the milder pemphigus erythematosus. (There are no breed predispositions recognized for the other 2 forms - p. vulgaris and p. vegetans).

How is ... inherited?:

unknown

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Pemphigus foliaceus and erythematosus develop around 4 years of age. P. erythematosus is thought to be a milder form of p. foliaceus. Both conditions begin with pustular, crusty lesions on the face and ears. However with p. foliaceus, the lesions spread to the feet, the groin and other areas; there may be itching and pain; and severely affected dogs may lose their appetite and become depressed.

Loss of pigment in the nose is common with both forms of pemphigus, and this results in photodermatitis - increased sensitivity to the sun's rays so that the condition is worse in sunny weather.

How is ... diagnosed?:

P. foliaceus is the most commonly seen form of pemphigus; however it is still uncommon. Your veterinarian will base the diagnosis on your history of how the condition developed, physical examination of your dog, and tests such as skin scrapings and smears, skin biopsy, and immune testing to rule out other causes of similar skin lesions such as a bacterial or fungal skin infection, mites, seborrhea, dermatomyositis, and lupus erythematosus.

How is ... treated?:

Treatment is based on suppressing the inappropriate immune response. For pemphigus foliaceus, steroids (as a cream, or orally as a tablet - prednisone) are used to accomplish this. Once the condition is under control, your veterinarian will reduce the dosage to every second day to avoid the side effects which can occur with these drugs. Long term treatment is generally necessary. Where prednisone is not effective (as is sometimes the case), your veterinarian will try other immunomodulating drugs or chrysotherapy (gold salts).

For dogs that have lost pigment in the nose, protection against the sun is important to prevent flare-ups of the condition. Keep your dog out of the sun between 10:00 and 3:00 and/or use suncreens on the nose with SPF of 15 or higher.
The milder form, pemphigus erythematosus, may be successfully treated with sun avoidance and glucocorticoids applied to the skin. If this is ineffective, oral glucocorticoids or other drugs may be required.
For the veterinarian: A combination of tetracycline and niacinamide has been used with some success in dogs with p. erythematosus (Scott, 1995 below).

For the veterinarian:

Multiple skin biopsies will increase the chances of finding diagnostic histologic changes. Direct immunofluorescence or immunohistochemical testing may or may not be helpful. These tests have relatively low sensitivity and specificity.

Breeding advice:

It is advisable not to use affected dogs in breeding programmes, even though inheritance for these conditions has not been worked out.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Scott, D.W., Miller, W.H., Griffin, C.E. 1995. Immunologic Skin Diseases. In Muller and Kirk's Small Animal Dermatology. p. 500-518. W.B. Saunders Co., Toronto.

Selective IgA deficiency

roblib — Tue, 20 Apr 2010 17:27:45 +0000

What is ... ?:

Immunoglobulins are proteins that function as antibodies and thus, provide immune protection. Immunoglobulin A (IgA) is important in protecting body surfaces, which include the skin, and the respiratory, digestive and reproductive tracts.

Dogs with IgA deficiency are prone to recurrent infections and the development of allergies (eg. atopy or food allergies) or immune-mediated diseases.

How is ... inherited?:

unknown.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Dogs with IgA deficiency usually have problems from a young age. They may have recurring skin, respiratory, gastrointestinal or urinary tract infections. The typical signs you might see include pustules and scratching, sneezing or nasal discharge, prolonged or recurring diarrhea, frequent or painful urination (cystitis - bladder infection).

These dogs are also prone to develop allergies or immune-mediated disorders.

How is ... diagnosed?:

Your veterinarian may suspect an immune deficiency if your dog is having recurring or frequent infections, especially of the skin. S/he will take a blood sample to measure your dog's immunoglobulin levels, which will show reduced or absent IgA.

How is ... treated?:

The various infections, allergies, or autoimmune disorders associated with IgA deficiency are treated as required. Different treatments to stimulate the immune system itself have been tried with varying success.

For the veterinarian: Staphylococcal phage lysate and Propionibacterium acnes vaccine are 2 immunomodulating agents which have been shown to enhance antibody production, and assist in the treatment of recurrent staphylococcal pyodermas in dogs.

For the veterinarian:

Serum IgA levels are low in all puppies, but by 4 months have reached levels where normal and IgA deficient dogs can be differentiated. However serum IgA only reaches maximal levels at 15 to 18 months of age, so it is important to age match when comparing.

Low IgA levels may be found in clinically normal dogs (who likely have normal secretory levels but not serum levels). IgG and/or IgM may be elevated in a compensatory manner. IgA deficiency diagnosed in dogs less than a year of age may be transient.

Breeding advice:

Affected animals should not be bred, and it is prudent to avoid breeding close relatives as well.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Severe combined immunodeficiency (SCID)

roblib — Tue, 27 Apr 2010 19:29:53 +0000

What is ... ?:

SCID is the most severe of the inherited immunodeficiency disorders. As the name implies, there is defective development of all components of the immune system. Pups are affected at a very young age, and are susceptible to a variety of infections.

How is ... inherited?:

This is an X-linked recessive trait. This means only males are clinically affected. However females can carry the trait and there is a 50% chance they will pass it to their male offspring.

What breeds are affected by ... ?:

What does ... mean to your dog & you?:

Pups are usually affected by 3 weeks of age with problems like diarrhea, skin and ear infections, and respiratory infections - all of which respond poorly or not at all to antibiotics. These pups have stunted growth and most will die by 3 or 4 months, of severe bacterial or viral infections (commonly distemper). Male siblings of affected pups may have died of "fading puppy syndrome" or other vague conditions.

How is ... diagnosed?:

This disorder is uncommon. Your veterinarian may begin to suspect an immune defiency when your pup has recurring illnesses that are very difficult to treat. Laboratory tests will help with the diagnosis.

How is ... treated?:

In affected people, the only successful treatment for this disorder is a bone marrow transplant which at present is not technically practical in dogs.

Secondary infections are treated as required, but there is generally a poor response.

For the veterinarian:

Lab tests show normal numbers of circulating B lymphocytes and variable IgM, but low to absent IgG and IgA. There are low to normal numbers of circulating T lymphocytes, which are non-functional.

On post-mortem, these dogs have a very small, dysplastic thymus and a profound lymphoid hypoplasia. (It may be difficult to detect any lymph nodes).
Recent genetic sequencing has located the specific defect, with the actual mutation varying with the breed. A genetics laboratory (if available) can test for the defect, but at present there is no commercial test.

Breeding advice:

The mother of an affected dog is a carrier of the disorder and should not be used for breeding. Female siblings, although clinically normal, have a 50% chance of being a carrier and should also not be used in breeding programmes.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Ackerman, L. 1999. The Genetic Connection: A Guide to Health Problems in Purebred Dogs. p. 100. AAHA Press, Lakewood, Colorado.

Felsburg, P.J. 1992. Primary immunodeficiencies. In J.D. Bonagura and R.W. Kirk (eds) Kirk's Current Veterinary Therapy XI Small Animal Practice p. 448-453. W.B. Saunders Co., Toronto.

Weimaraner immunodeficiency

roblib — Tue, 27 Apr 2010 19:32:35 +0000

What is ... ?:

In this disorder, there are deficiencies in a part of the immune system. The result is an increased susceptibility to various types of infection.

How is ... inherited?:

unknown.

What breeds are affected by ... ?:

Weimaraner

What does ... mean to your dog & you?:

Dogs with this condition are affected at a young age with recurring fevers and infections of the skin and muscle.

How is ... diagnosed?:

This disorder is uncommon. Your veterinarian may begin to suspect an immune deficiency when your pup has recurring infections. Laboratory tests will help with the diagnosis.

How is ... treated?:

Antibiotics are used as needed to treat the infections. There is no treatment for the condition itself.

For the veterinarian:

Circulating IgG and IgM levels are decreased, and neutrophil function is impaired. (Both humoral and phagocytic functions are affected with this disorder.)

Breeding advice:

Affected dogs should not be used for breeding, and close relatives should be screened to determine that they have normal neutrophil function and immunoglobulin levels before being considered for a breeding programme.

FOR MORE INFORMATION ABOUT THIS DISORDER, PLEASE SEE YOUR VETERINARIAN.

Resources:

Ackerman, L. 1999. The Genetic Connection: A Guide to Health Problems in Purebred Dogs. p. 100. AAHA Press, Lakewood, Colorado.