Craniomandibular osteopathy, also known as lion's jaw, is a developmental disease in dog

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 causing extensive bony changes in the mandible

Mandible

The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...

 and skull

Skull

The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...

. In this disease there is a cyclical resorption of normal bone and replacement by immature bone along the inner and outer surfaces of the affected bones. It usually occurs between the ages of 3 and 8 months. Breeds most commonly affected include the West Highland White Terrier

West Highland White Terrier

The West Highland White Terrier, commonly known as the Westie, is a Scottish breed of dog with a distinctive white coat. The modern breed is descended from a number of breeding programes of white terriers in Scotland prior to the 20th century...

, Scottish Terrier

Scottish Terrier

The Scottish Terrier , popularly called the Scottie, is a breed of dog. Initially one of the highland breeds of Terrier that were grouped under the name of Skye Terrier, it is one of five breeds of terrier that originated in Scotland, the other four being the modern Skye, Cairn, Dandie Dinmont, and...

, Cairn Terrier

Cairn Terrier

The Cairn Terrier is the oldest of the terrier breeds, originating in the Scottish Highlands and recognized as one of Scotland's earliest working dogs...

, and Boston Terrier

Boston Terrier

The Boston Terrier is a breed of dog originating in the United States of America. This "American Gentleman" was accepted in 1893 by the American Kennel Club as a non-sporting breed. Color and markings are important when distinguishing this breed to the AKC standard. They should be either black,...

. It is rare in large breed dogs, but it has been reported. Symptoms include firm swelling of the jaw, drooling, pain, and difficulty eating. It is an inherited disease, especially in Westies, in which it has been recognized as an autosomal recessive trait. 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...

 has also been indicated as a possible cause, as has E. coli

Escherichia coli

Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...

infection, which could be why it is seen occasionally in large breed dogs. Growth of lesions will usually stop around the age of one year, and possibly regress. This timing coincides with the normal completion of endochondral bone growth and ossification

Endochondral ossification

Endochondral ossification is one of the two essential processes during fetal development of the mammalian skeletal system by which bone tissue is created. Unlike intramembranous ossification, which is the other process by which bone tissue is created, cartilage is present during endochondral...

. If the disease is extensive, especially around the tympanic bulla (middle ear), then the prognosis

Prognosis

Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...

 is guarded.

A similar disease seen in young Bullmastiff

Bullmastiff

The Bullmastiff is a large breed of domestic dog. It has a solid build and a short muzzle. The Bullmastiff shares the characteristics of Molosser dogs, and was originally developed by 19th-century gamekeepers in England to guard estates and immobilize poachers. The breed's bloodlines are drawn from...

s is known as calvarial hyperostotic syndrome. It is also similar to human infantile cortical hyperostosis

Infantile cortical hyperostosis

Infantile cortical hyperostosis is a self-limited inflammatory disorder of infants that causes bone changes, soft tissue swelling and irritability. The disease may be present at birth or occur shortly thereafter. The cause is unknown. Both familial and sporadic forms occur...

. It is characterized by irregular, progressive bony proliferation and thickening of the cortical bone of the calvaria

Calvaria (skull)

The calvaria is the upper part of the cranium and surrounds the cranial cavity containing the brain.The calvaria is made up of the frontal, occipital and right and left parietals....

, which is part of the skull. Asymmetry of the lesions may occur, which makes it different from craniomandibular osteopathy. Symptoms include painful swelling of the skull, fever, and lymph node

Lymph node

A lymph node is a small ball or an oval-shaped organ of the immune system, distributed widely throughout the body including the armpit and stomach/gut and linked by lymphatic vessels. Lymph nodes are garrisons of B, T, and other immune cells. Lymph nodes are found all through the body, and act as...

swelling. In most cases it is self-limiting.