Hypertrophic osteodystrophy
Encyclopedia
Hypertrophic Osteodystrophy (HOD) is a bone disease that occurs in fast-growing large and giant breed dog
s. The disorder is sometimes referred to as metaphyseal osteopathy, and typically first presents between the ages of 2 and 7 months. HOD is characterized by decreased blood flow to the metaphysis (the part of the bone adjacent to the joint) leading to a failure of ossification
(bone formation) and necrosis
and inflammation of cancellous bone. The disease is usually bilateral in the limb bones, especially the distal
radius
, ulna
, and tibia
.
The Weimaraner, Irish Setter, Boxer, German Shepherd, and Great Dane breeds are heavily represented in case reports of HOD in the veterinary literature, but the severity of symptoms and possible etiology may be different across the breeds. For example, familial clustering of the disease has been documented in the Weimaraner, but not in other breeds. The disease in the Weimaraner and Irish Setter can be particularly severe, with significant mortality observed in untreated dogs. The classical age of onset is typically 8 to 16 weeks of age, with males and females equally affected.
uptake, increased vitamin (other than C) and mineral uptake, and infection with canine distemper
virus(CDV). Decreased Vitamin C uptake has been dismissed as a cause, but excessive calcium
supplementation remains a possibility. There is no evidence over-feeding is a significant cause. In Weimaraner
s, recent vaccination
with a modified live vaccine
has been a suspected cause, partly because HOD often presents immediately after a vaccination, and partly because of the autoimmune nature of the disorder. The canine distemper vaccination in particular has been a suspected causal factor due to the significant number of overlapping symptoms observed between systemically affected HOD puppies and dogs suffering from distemper, but to-date, no definitive linkage has been demonstrated. The cause of canine HOD largely remains unknown. However, because of the familial clustering, HOD in the Weimaraner is suspected to have a genetic, or partly genetic, origin.
The relatively high incidence of HOD in Weimaraners and the potential for severe illness if not treated appropriately has led the Health Committee of the Weimaraner Club of America to recommend an alternative to the traditional vaccination protocol--the goal being to confer the maximum level of protection with the minimum number of vaccinations. Combination vaccines are given at 8 weeks and 12 weeks, and an antibody titer is recommended at 15-16 weeks to confirm immunity. Only puppies that show no evidence of antibody production in the titer should be given the third vaccination in the series. See revised vaccination guidelines as of February 2011.
of the long bones that is observed. Other bones may be affected, particularly the ribs, the metacarpal bones, the mandible, and the scapula. Lameness may present as mild limping or more severely as a reluctance or inability to stand. In some breeds and/or individuals, the stance of an HOD puppy as observed from behind has sometimes been described as “cow-hocked.” Shaking of limbs and a reluctance to put full body weight on the front legs is often observed. Sometimes the puppy will exhibit a characteristic “roaching” or arching of the spine when standing (see Figure 2).
Lameness is accompanied by pain upon palpation of affected bones, warmth in the limb as felt by the inside of the clinician’s wrist, depression, and loss of appetite. Limb involvement is usually bilateral, typically involves the distal radius and ulna, and may be episodic. There is evidence to suggest that most dogs recover after one episode, but some relapse. Dogs suffering systemic manifestations of the disorder often have poorer prognoses. Systemic manifestations include fever, multiple body organ inflammation, nasal and ocular discharge, Diarrhea, hyperkeratosis of the foot pads, pneumonia, and tooth enamel hypoplasia (many of these symptoms overlap with symptoms of CDV). Because early diagnosis must be based on clinical signs, to the extent possible, other disorders should be ruled out (e.g., nutritional bone disease, and osteochondrosis).
may be observed to have an uneven radiolucent zone parallel to the physis with a thin band of increased radiodensity directly bordering the physis. Early stage radiographic changes have sometimes been described as having a "moth-eaten" appearance (see Figure 3). As the disease progresses, the radiolucent line may disappear and radiodensity may increase in the affected area as the body attempts to repair damage. Relapses can cause new radiolucent lines. This area is often followed by a dark line at the metaphysis, which may progress to new bone growth on the outside of that area. This area represents microfractures in the metaphysis and bone proliferation to bridge the defect in the periosteum
.
s) and supportive care. Dogs presenting with severe, systemic symptoms not responding to NSAID treatment require more intensive treatment. The Weimaraner and Irish Setter American Kennel Club
(AKC) parent clubs advocate the use of immunosuppressive doses of corticosteroid
s, supplemented with antibiotics and antacids (to counteract increased production of stomach acid by the corticosteroids). More severe cases that are not recognized and treated early often require IV fluids, electrolytes, nutritional support, and significant nursing care to achieve successful results. AKC parent clubs have supported research into the genetic causes of HOD, and have reported fairly good success using this protocol, saving many puppies from unnecessary suffering, deformity, and death.
NOTE: Supplementation of Vitamin C
is contraindicated due to an increase in calcium levels in the blood, possibly worsening the disease.
Dog
The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...
s. The disorder is sometimes referred to as metaphyseal osteopathy, and typically first presents between the ages of 2 and 7 months. HOD is characterized by decreased blood flow to the metaphysis (the part of the bone adjacent to the joint) leading to a failure of ossification
Ossification
Ossification is the process of laying down new bone material by cells called osteoblasts. It is synonymous with bone tissue formation...
(bone formation) and necrosis
Necrosis
Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...
and inflammation of cancellous bone. The disease is usually bilateral in the limb bones, especially the distal
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
radius
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
, ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
, and tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
.
The Weimaraner, Irish Setter, Boxer, German Shepherd, and Great Dane breeds are heavily represented in case reports of HOD in the veterinary literature, but the severity of symptoms and possible etiology may be different across the breeds. For example, familial clustering of the disease has been documented in the Weimaraner, but not in other breeds. The disease in the Weimaraner and Irish Setter can be particularly severe, with significant mortality observed in untreated dogs. The classical age of onset is typically 8 to 16 weeks of age, with males and females equally affected.
Speculated causes of HOD
Causes have been speculated to include decreased Vitamin CVitamin C
Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress...
uptake, increased vitamin (other than C) and mineral uptake, and infection with canine distemper
Canine distemper
Canine distemper is a viral disease that affects animals in the families Canidae, Mustelidae, Mephitidae, Hyaenidae, Ailuridae, Procyonidae, Pinnipedia, some Viverridae and Felidae...
virus(CDV). Decreased Vitamin C uptake has been dismissed as a cause, but excessive calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
supplementation remains a possibility. There is no evidence over-feeding is a significant cause. In Weimaraner
Weimaraner
The Weimaraner is a dog that was originally bred for hunting in the early 19th century. Early Weimaraners were used by royalty for hunting large game such as boar, bear, and deer. As the popularity of large game hunting began to decline, Weimaraners were used for hunting smaller animals like...
s, recent vaccination
Vaccination
Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens...
with a modified live vaccine
Vaccine
A vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
has been a suspected cause, partly because HOD often presents immediately after a vaccination, and partly because of the autoimmune nature of the disorder. The canine distemper vaccination in particular has been a suspected causal factor due to the significant number of overlapping symptoms observed between systemically affected HOD puppies and dogs suffering from distemper, but to-date, no definitive linkage has been demonstrated. The cause of canine HOD largely remains unknown. However, because of the familial clustering, HOD in the Weimaraner is suspected to have a genetic, or partly genetic, origin.
The relatively high incidence of HOD in Weimaraners and the potential for severe illness if not treated appropriately has led the Health Committee of the Weimaraner Club of America to recommend an alternative to the traditional vaccination protocol--the goal being to confer the maximum level of protection with the minimum number of vaccinations. Combination vaccines are given at 8 weeks and 12 weeks, and an antibody titer is recommended at 15-16 weeks to confirm immunity. Only puppies that show no evidence of antibody production in the titer should be given the third vaccination in the series. See revised vaccination guidelines as of February 2011.
Clinical Features
A primary characteristics of the condition is lameness. This is generally due to the swelling of the metaphysisMetaphysis
The metaphysis is the wider portion of a long bone adjacent to the epiphyseal plate. It is this part of the bone that grows during childhood; as it grows, it ossifies near the diaphysis and the epiphyses...
of the long bones that is observed. Other bones may be affected, particularly the ribs, the metacarpal bones, the mandible, and the scapula. Lameness may present as mild limping or more severely as a reluctance or inability to stand. In some breeds and/or individuals, the stance of an HOD puppy as observed from behind has sometimes been described as “cow-hocked.” Shaking of limbs and a reluctance to put full body weight on the front legs is often observed. Sometimes the puppy will exhibit a characteristic “roaching” or arching of the spine when standing (see Figure 2).
Lameness is accompanied by pain upon palpation of affected bones, warmth in the limb as felt by the inside of the clinician’s wrist, depression, and loss of appetite. Limb involvement is usually bilateral, typically involves the distal radius and ulna, and may be episodic. There is evidence to suggest that most dogs recover after one episode, but some relapse. Dogs suffering systemic manifestations of the disorder often have poorer prognoses. Systemic manifestations include fever, multiple body organ inflammation, nasal and ocular discharge, Diarrhea, hyperkeratosis of the foot pads, pneumonia, and tooth enamel hypoplasia (many of these symptoms overlap with symptoms of CDV). Because early diagnosis must be based on clinical signs, to the extent possible, other disorders should be ruled out (e.g., nutritional bone disease, and osteochondrosis).
Radiographic Features
Diagnosis relies on clinical signs and characteristic changes in radiographic images of the metaphyses. Bone changes can be observed on radiograph, and the disorder may progress to actual angular limb deformity. In the early stage of the illness, the metaphyseal area on X-rayX-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
may be observed to have an uneven radiolucent zone parallel to the physis with a thin band of increased radiodensity directly bordering the physis. Early stage radiographic changes have sometimes been described as having a "moth-eaten" appearance (see Figure 3). As the disease progresses, the radiolucent line may disappear and radiodensity may increase in the affected area as the body attempts to repair damage. Relapses can cause new radiolucent lines. This area is often followed by a dark line at the metaphysis, which may progress to new bone growth on the outside of that area. This area represents microfractures in the metaphysis and bone proliferation to bridge the defect in the periosteum
Periosteum
Periosteum is a membrane that lines the outer surface of all bones, except at the joints of long bones. Endosteum lines the inner surface of all bones....
.
Treatment
Treatment options have been controversial. Mild illness is often successfully treated with pain medication (usually NSAIDNon-steroidal anti-inflammatory drug
Nonsteroidal anti-inflammatory drugs, usually abbreviated to NSAIDs or NAIDs, but also referred to as nonsteroidal anti-inflammatory agents/analgesics or nonsteroidal Anti-inflammatory medicines , are drugs with analgesic and antipyretic effects and which have, in higher doses, anti-inflammatory...
s) and supportive care. Dogs presenting with severe, systemic symptoms not responding to NSAID treatment require more intensive treatment. The Weimaraner and Irish Setter American Kennel Club
American Kennel Club
The American Kennel Club is a registry of purebred dog pedigrees in the United States. Beyond maintaining its pedigree registry, this kennel club also promotes and sanctions events for purebred dogs, including the Westminster Kennel Club Dog Show, an annual event which predates the official...
(AKC) parent clubs advocate the use of immunosuppressive doses of corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
s, supplemented with antibiotics and antacids (to counteract increased production of stomach acid by the corticosteroids). More severe cases that are not recognized and treated early often require IV fluids, electrolytes, nutritional support, and significant nursing care to achieve successful results. AKC parent clubs have supported research into the genetic causes of HOD, and have reported fairly good success using this protocol, saving many puppies from unnecessary suffering, deformity, and death.
NOTE: Supplementation of Vitamin C
Vitamin C
Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress...
is contraindicated due to an increase in calcium levels in the blood, possibly worsening the disease.
Breeds at increased risk for HOD
- Alaskan MalamuteAlaskan MalamuteThe Alaskan Malamute is a generally large breed of domestic dog originally bred for use as a utilitarian dog and later an Alaskan sled dog. They are sometimes mistaken for a Siberian Husky, but in fact are quite different in many ways...
- BoxerBoxer (dog)Developed in Germany, the Boxer is a breed of stocky, medium-sized, short-haired dog. The coat is smooth and fawn or brindled, with or without white markings. Boxers are brachycephalic , and have a square muzzle, mandibular prognathism , very strong jaws and a powerful bite ideal for hanging on to...
- Chesapeake Bay RetrieverChesapeake Bay RetrieverThe Chesapeake Bay Retriever is a breed of dog belonging to the Retriever, Gundog, and Sporting breed groups. Members of the breed may also be referred to as a Chessie, CBR, or Chesapeake. The breed was developed in the United States Chesapeake Bay area during the 19th century...
- German Shepherd DogGerman Shepherd DogThe German Shepherd Dog , also known as an Alsatian or just the German Shepherd, is a breed of large-sized dog that originated in Germany. The German Shepherd is a relatively new breed of dog, with its origin dating to 1899. As part of the Herding Group, the German Shepherd is a working dog...
- Golden RetrieverGolden RetrieverThe Golden Retriever is a medium-sized breed of dog. They were historically developed as gundogs to retrieve shot waterfowl such as ducks and upland game birds during hunting and shooting parties. As such, they were bred to have a soft mouth to retrieve game undamaged and have an instinctive love...
- Great DaneGreat DaneThe Great Dane , also known as German Mastiff or Danish Hound , is a breed of domestic dog known for its giant size...
- Irish SetterIrish SetterThe Irish Setter , is a setter, a breed of gundog and family dog. The term Irish Setter is commonly used to encompass the show-bred dog recognized by the American Kennel Club as well as the field-bred Red Setter recognised by the Field Dog Stud Book....
- Japanese Akita
- Labrador RetrieverLabrador RetrieverThe Labrador Retriever is one of several kinds of retriever, a type of gun dog. A breed characteristic is webbed paws for swimming, useful for the breed's original purpose of retrieving fishing nets. The Labrador is the most popular breed of dog by registered ownership in Canada, the United...
- WeimaranerWeimaranerThe Weimaraner is a dog that was originally bred for hunting in the early 19th century. Early Weimaraners were used by royalty for hunting large game such as boar, bear, and deer. As the popularity of large game hunting began to decline, Weimaraners were used for hunting smaller animals like...