Cats can be born with or may inherit several different kinds of skin abnormalities. Some inherited skin disorders can become visible weeks to months after birth. Most of these conditions are uncommon to rare. Some occur with greater frequency in particular breeds of cats.
Epitheliogenesis imperfecta, also called aplasia cutis, might be described as missing or absent skin. It is a congenital condition of unknown cause and is rare in cats. Animals with epitheliogenesis imperfecta have failed to develop part or all of the layers of the skin. As a result, the animal is born with ulcers, or areas lacking any skin covering. One or more claws may also be missing. The condition can be fatal if it involves large portions of the skin. Small defects can be surgically corrected.
Animals can be born either totally or partially without hair. Hairlessness can also develop later in life. The hair loss can result in body-wide baldness, but it often develops in patterns, such as being associated with hair color or not affecting the limbs. These defects can be associated with abnormal teeth, claws, and eyes, or with skeletal and other developmental defects. Hairless breeds of cats, such as the Sphinx, have been bred for these defects. All animals with abnormal hair development are prone to hair follicle infections, and inflammation caused by foreign objects in the hair follicles.
In cats, hair growth abnormalities known as follicular dysplasia have been reported in the Devon Rex. Hair shaft structural abnormalities called pili torti are known to occur in the American Wirehaired Cat.
Some skin color abnormalities may be acquired, while others are hereditary. Abnormalities in skin and coat color are sometimes related. Some of the associations are mentioned in hereditary hair loss (see above).
Albinism is rare in cats. True albinism is always associated with pink or pale irises and with visual defects and increased risk of skin damage from sunlight. Albinism is different from extreme white spotting. Some animals with extreme piebaldism (spotted or blotched with black and white) or dominant white have associated nervous system abnormalities or deafness in one or both ears. About 75% of white cats with 2 blue eyes are deaf. Albino and white skin on piebald cats is subject to solar damage and sun-induced skin cancer, especially where the hair is short or thin (such as on the ears).
A defect in the cells that produce color pigment can result in a "diluted" coat color (called color dilution). For example, color dilution in Persian cats can result in the "blue smoke" coat color. This blue smoke color is associated with Chédiak-Higashi syndrome, which causes defects in certain blood cells. These cats may bleed abnormally, have decreased immune function, and have a shortened life span.
The areas of orange coat color in male tricolor cats (calico and tortoiseshell) are a result of a genetic abnormality. These cats are unable to produce offspring.
Lentigo occurs in orange and orange-faced male cats. It is marked by the development of pigmented spots. Marks are first seen on the lips and eyelids at 1 year of age. Marks later develop on the nose and lips. Lentigo spots are not precancerous and have no medical consequence.
Vitiligo is hereditary but not noticeable at birth. The onset is usually in young adulthood. The condition is most common in Siamese cats. Affected cats develop bleached areas of skin that occasionally also involve the hair coat and claws. Most patches are on the face, especially the bridge of the nose or around the eyes. Color loss may wax and wane. Complete remission may occur but is rare. Vitiligo causes no other health problems. No treatment is available. Treatments used in people with vitiligo are unlikely to help animals.
Some skin diseases are genetic defects that affect the structural integrity of the skin. Cutaneous asthenia (also known as dermatosparaxis or Ehlers–Danlos syndrome) is a group of syndromes characterized by defects in collagen production. Affected animals develop loose, unusually elastic, fragile skin along with loose joints and other connective tissue dysfunctions. These syndromes have been seen in Himalayan and domestic shorthair cats. For Himalayan cats, the disease is a recessive genetic characteristic, meaning that some cats will carry the gene without showing signs of the disorder. In some families of domestic shorthair cats, the disease is a dominant genetic characteristic, so all cats of these families that carry the gene will show clinical signs.
The signs of these syndromes include fragile skin (present from birth), wounds that heal with thin scars, delayed wound healing, hanging skin, eye problems, and pockets of blood outside the bloodstream (hematomas) and sacs or cysts filled with fluid (hygromas).
Diagnosis in cats includes assessment of signs, measurement of skin elasticity, and laboratory tests on the collagen structure of skin samples. Prior to diagnosing cutaneous asthenia, your veterinarian will want to eliminate other disorders of acquired rather than hereditary skin fragility as a cause of the skin problems. Cutaneous asthenia is not usually fatal in cats, although older animals develop hanging folds of skin and often have extensive scarring.
Epidermolysis bullosa syndromes are a group of hereditary congenital defects in the zone between the dermis and epidermis. Minor skin trauma results in separation of the dermal and epidermal skin layers and blisters that soon rupture, leaving glistening, flat ulcers. Skin damage may be present at birth or develop within the first weeks of life. The most severe damage occurs on the feet, mouth, face, and genitals. The claws and footpads can detach and fall off. Most occurrences of this disease are fatal.
This disease has been seen in Siamese, domestic shorthair, and Persian cats.
Congenital tumors are rare in cats. Abnormal growth and spread of mast cells in the skin (benign familial cutaneous mastocytosis) has been reported in young Siamese cats. This rare, inherited condition causes skin to thicken and have a leathery, bark-like appearance. Intense itching is evident. Treatment includes medication to control itching and prevent self-inflicted skin damage.
Abnormal growth of mast cells also causes urticaria pigmentosa in cats. Affected cats have multiple crusted bumps on the head, neck, and legs. This hereditary condition is diagnosed by skin biopsy.
Also see professional content regarding congenital and inherited skin disorders.