Chronic superficial keratitis (CSK), also known as pannus or Uberreiter's disease, is an inflammatory condition of the
cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...
in
dog
The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
s, particularly seen in the
German Shepherd. Both eyes are usually affected. The corneas gradually become pigmented and infiltrated by blood vessels, and the dog may eventually become blind.
Signs and symptoms
CSK is usually a bilateral progressive condition, however the lesions are not symmetrical nor are they painful. Signs include pigmentation and vascularization of the cornea (extension of blood vessels onto the cornea). It is usually first seen at the lateral (temporal) limbus (the junction between the cornea and
sclera
The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber. In humans, and som ...
), although it eventually can extend from any part of the limbus to cover the entire cornea. Severe cases can cause blindness. Although CSK is usually identifiable by the appearance of the eye and the breed of the affected dog,
cytology will reveal the presence of lymphocytes and
plasma cell
Plasma cells, also called plasma B cells or effector B cells, are white blood cells that originate in the lymphoid organs as B lymphocytes and secrete large quantities of proteins called antibodies in response to being presented specific substan ...
s.
Cause
CSK is
immune-mediated
An immune disorder is a dysfunction of the immune system. These disorders can be characterized in several different ways:
* By the component(s) of the immune system affected
* By whether the immune system is overactive or underactive
* By whether t ...
in nature, characterized by an infiltration of
white blood cell
White blood cells, also called leukocytes or leucocytes, are the cell (biology), cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and de ...
s into the superficial stroma of the cornea. These cells are predominantly
CD4
In molecular biology, CD4 (cluster of differentiation 4) is a glycoprotein that serves as a co-receptor for the T-cell receptor (TCR). CD4 is found on the surface of immune cells such as T helper cells, monocytes, macrophages, and dendritic ...
-expressing
T lymphocyte
A T cell is a type of lymphocyte. T cells are one of the important white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell rec ...
s and to a lesser extent
CD8-expressing T cells. The CD4-expressing T-cells secrete gamma
interferon
Interferons (IFNs, ) are a group of signaling proteins made and released by host cells in response to the presence of several viruses. In a typical scenario, a virus-infected cell will release interferons causing nearby cells to heighten the ...
, which causes expression of the
major histocompatibility complex
The major histocompatibility complex (MHC) is a large locus on vertebrate DNA containing a set of closely linked polymorphic genes that code for cell surface proteins essential for the adaptive immune system. These cell surface proteins are calle ...
class II molecules in the cells of the cornea. These class II molecules cause further inflammation by interacting with the T cells and triggering an immune response.
Ultraviolet light
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
is important in the genesis of the disease which is seen at higher prevalence at elevated altitude and has a seasonal variation with most cases occurring in the summer. There is likely also a genetic component to the cause of CSK due to its predominance in certain breeds.
Treatment
Treatment of CSK is usually with topical
corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are involv ...
s or topical
cyclosporine, but any treatment only controls and reduces the inflammation rather than providing a cure. Other investigated treatments include
pimecrolimus, a derivative of
ascomycin
Ascomycin, also called Immunomycin, FR-900520, FK520, is an ethyl analog of tacrolimus (FK506) with strong immunosuppressant properties. It has been researched for the treatment of autoimmune diseases and skin diseases, and to prevent rejection ...
that interferes with T cell activation and inhibits the production of inflammatory
cytokine
Cytokines are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are peptides and cannot cross the lipid bilayer of cells to enter the cytoplasm. Cytokines have been shown to be involved in autocrin ...
s.
Strontium-90 radiation therapy
Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radia ...
is also used to treat CSK. Canine
sunglasses
Sunglasses or sun glasses (informally called shades or sunnies; more names below) are a form of protective eyewear designed primarily to prevent bright sunlight and high-energy visible light from damaging or discomforting the eyes. They can s ...
have also been used to help protect the eyes of dogs with CSK to prevent further damage from ultraviolet radiation.
Epidemiology
Chronic superficial keratitis is most commonly seen in
German Shepherds, but it is also found in
Belgian Tervuren
The Belgian Shepherd (also known as the Belgian Sheepdog, Belgian Malinois, or the Chien de Berger Belge) is a Dog breed, breed of medium-sized herding dog from Belgium. While predominantly considered a single breed, it is bred in four disti ...
s,
Greyhounds,
Siberian Huskies,
Australian Shepherds, and
Border Collies.
See also
*
Uveal cyst
*
Meibomian cyst
References
{{Reflist
Dog diseases