Types of Disorders

Immune-mediated skin disorders
Skin disease may result from deficiencies in immune system function. In cats, the most common cause of immune deficiency is infection with retroviruses, FIV or FeLV, and cats with these chronic infections are subject to repeated bouts of skin infection and abscesses. This category also includes hypersensitivity disorders and eosinophilic skin diseases such as atopic dermatitis, miliary dermatitis and feline eosinophilic granuloma and skin diseases caused by autoimmunity, such as pemphigus and discoid lupus.

Infectious skin diseases
The most important infectious skin diseases of cats is ringworm or dermatophytosis. Other cat skin infections include parasitic diseases like mange and lice infestation.

Other ectoparasites, including flea and tick infestations are not considered directly contagious but are acquired from an environment where other infested hosts have established the parasite's life cycle.

Another common skin infection is cat bite abscess. A mixture of bacteria introduced by a bite wound cause infections in pockets under the skin and affected cats often show manic depression and fever.

Hereditary and developmental skin diseases
Some diseases are inherent abnormalities of skin structure or function. These include skin fragility syndrome (Ehlers-Danlos), hereditary hypotrichosis and congenital or hereditary alopecia.

Cutaneous manifestations of internal diseases
Some systemic diseases can become symptomatic as a skin disorder. In cats this includes one of the most devastating cat skin disorders, feline acquired skin fragility syndrome, which can come from starvation or over-treatment with cortisone-like drugs or with diabetes, FIP or Cushings Disease.

Nutrition related disorders
Today, nutritionally balanced diets are fed, and therefore nutritional deficiencies have become uncommon. However, these nutritional related disorders can arise if the cat's food intake decreases, interactions between ingredients or nutrients occur, mistakes are made during formulation or manufacturing, and lengthy storage time. Nutritional related skin disorders usually result in excesses or not enough oil production known as sebum, and keratinization toughening of the outer layer of the skin. This can result in dandruff, redness known as erythema, hair loss, greasy skin, and diminished hair growth.

Minerals
Zinc is important for the skins function as it is involved in DNA and RNA, and therefore important for cells that divide rapidly. A deficiency in the zinc mainly results in skin disorders in adult cats, but also results in growth oddities. The skin of a cat deficient in zinc would likely have erythema, hair loss, crusty and scaly skin on its limbs or tail. The coat of the cat becomes dull and tough; however, zinc deficiency has not been reported in cats. Similarly, copper can affect coat health of cats, when deficient will cause fading of coat color, and weakened skin leading to lesions.

Protein
The hair of a cat is made of mainly protein, and cats need about 25-30% protein in their diets, much higher than what a dog needs. A deficiency in protein usually happens when kittens are fed dog food, when they need much higher protein, and when low-protein diets are fed improperly. If a cat has a protein deficiency the cat will lose weight, then show poor coat condition such as scaly skin, dull, thinning, weak, and patchy hair. To remedy this a diet with adequate amounts of protein must be fed.

Essential fatty acids
Cats must have both linoleic acid, and unlike the dog also arachidonic acid due in their diet, due to their low production of the δ-6 desaturase enzyme. A deficiency in these fatty acids can occur if the fats in the cat's food are oxidized and become rancid from improper storage. A cat will be deficient for many months prior to seeing clinical signs in the skin, after which the skin will become scaly, and greasy while the coat will become dull. To treat a cat with a lack of fatty acids, the ratio of n-3 to n-6 fatty acid must be corrected and supplemented (Hensel 2010).

Vitamin A
Cats cannot synthesize vitamin A from plant beta-carotene, and therefore must be supplemented with retinol from meat. A deficiency in vitamin A will result in a poor coat, with hair loss, with scaly and thickened skin. However an excess of vitamin A, called hypervitaminosis A, can result from over feeding cod liver oil, and large amounts of liver. Signs of hypervitaminosis A are overly sensitive skin, and neck pain causing the cat to be unwilling to groom its self, resulting in a poor coat. Supplementing vitamin A with retinol to a deficient cat, and feeding a balanced diet to a cat with hypervitaminosis A will treat the underlying nutritional disorder.

Vitamin B
The cat must have a supply of niacin, as cats cannot convert tryptophan into niacin like dogs. However, diets high in corn and low in protein can result in skin lesions and scaly, dry, greasy skin, with hair loss. Another B vitamin, biotin, if deficient causes hair loss around the eyes and face. A lack of B vitamins can be corrected by supplementing with a vitamin B complex, and brewers yeast.