German Shepherd dogs
Pannus: Corneal Inflammation in the German Shepherd Dog
(German Shepherd Dog Keratitis, Keratitis Ueberreiter)
By Dr. W. Neumann
What is Pannus?
German Shepherd Dog Keratitis [pannus], medical name: keratitis superficialis vasulosa pannosa pigmentosa chronica, is a chronic inflammation of the corneal surface and, in most cases, of the conjunctiva of the eye. In veterinary medicine the disease is also known as Keratitis Ueberreiter, named after the man who first described it (1). The reason it is called German Shepherd Dog Keratitis is because the disease is found predominantly in German Shepherds and is only rarely seen in other breeds (e.g., Collie, Poodle, Dachshund, Greyhound, mixed breeds).
What are the Symptoms of Pannus?
The disease generally manifests itself in dogs between the ages of three and five. It first appears in the outer regions of the cornea and, in almost all cases, affects both eyes simultaneously. Vascular granules and connective tissue establish themselves at the border between the sclera and the cornea, which is often variously pigmented, and grow into the top-most layers of the cornea. This results in the formation of an opaque, cherry-coloured spot with an uneven surface often ringed by a fatty, grayish-white band.
As the disease progresses, pigment forming cells migrate from the outer edges into the afflicted area, giving the spot, which expands toward the center of the cornea, a gray-pink to a variegated brown and black appearance. Frequently there will be a concurrent inflammation dependent reddening of the conjunctiva. Without treatment, the inflammation will progress to cover the entire cornea and can lead to total blindness.
What Causes Pannus?
In the past, discussions centered around infectious agents. Although the precise origins of the disease are still not known in detail, it is now generally accepted to be a derailment of the immune system whereby the organism, in an autoimmune response, produces antibodies or toxic immune cells against its own tissues. At the onset of the disease additional factors are involved: those naturally produced by the body (endogenic), and those which are external (exogenic). The endogenic factor in this context appears to be a breed-dependent inherited predisposition to this disease in the German Shepherd Dog, although the hereditable succession is not known at this time. The predominant exogenic factor is ascribed to ultraviolet rays in sunlight as the trigger of pannus which explains the increased incidence of the disease during sunny months.