Hyperpigmentation in Cats

Hyperpigmentation is the darkening of the skin on an anima. This may happen to humans, dogs, and — you guessed it — cats too. Hyperpigmentation can happen for all sorts of reasons and for no reason at all, but we’ll get into that shortly.

Orange cats seem to be more likely to have hyperpigmentation of the skin, but any color cat can develop this condition. Hyperpigmentation can occur on the skin, mucosal membranes of the mouth and nose, or the eyes of a feline. Skin hyperpigmentation typically occurs in small patches or spots on the feline.

The symptoms of hyperpigmentation are usually mild and can vary depending on the root cause. Hair loss or thinning may accompany the appearance of dark patches. Sometimes, the hair around the affected area will also change color. Some cats have no symptoms other than skin discoloration, whereas other felines develop pockets of pus underneath the discolored area if there is an infection present. Skin discoloration due to tumors or injury may cause itching and scratching of the affected area and there might be some associated pain.

There are a number of reasons cats may develop hyperpigmentation. Here are some of the most common:

Lentigo 

Lentigo is particularly common in cats with orange coloration in their fur. These black spots commonly affect the gums, mouth, eyelids, and nose. Experts liken this condition to freckles or age spots in humans, and no treatment is necessary. 

Tumors

Bowen's disease tumors (a type of squamous cell carcinoma), basal cell tumors, and mast cell tumors can also cause hyperpigmentation in cats. If these growths are cancerous, they may cause a range of symptoms like lethargy, pain, and lesions. You may or may not be able to easily feel the tumors.

Apocrine cysts

Apocrine cysts are cysts that form around one or more hair follicles on the cat's skin. These typically fill with fluid or pus and may disappear on their own or have to be surgically removed. These are typically harmless and are most common in senior felines. They tend to be dark.

Fungal infections

Fungal infections can also cause darkening and scaling of the skin. Fungal infections are caused by the growth of fungus on the skin and are often contagious to other felines. They can occur secondary to e.g. allergic skin disease.

Diagnosis of hyperpigmentation is usually made visually, though determining the root cause may take more time and tests. Blood tests may be necessary to check white blood cell counts to ensure there isn't an underlying illness at play. Vets may also collect skin cells or a fur pluck from the area to test them for a fungal infection.

If there is a growth under the affected area, vets may want to take a biopsy or fine-needle aspiration of the area. Biopsies are a surgical procedure whereas fine needle aspirations can be done in the exam room. The vet will take a small needle and remove some cells from the affected area. They will then examine the tissue under a microscope (or send them to an external laboratory) to determine if the cells are normal or if further testing needs to be done.

Treatment for hyperpigmentation in felines depends on the diagnosis. If the diagnosis is lentigo, no treatment is necessary. Hyperpigmentation caused by growths may require surgical removal and chemotherapy if they're cancerous. Vets typically administer antifungal creams and medications to cats dealing with skin darkening due to fungal infections. They may also prescribe a medicated shampoo for use on the affected area.

If the diagnosis is cancerous growths, the recovery period can be a lengthy process. It may take months of chemotherapy to eliminate the cancer cells. 

The recovery period for fungal infections is much quicker. You may see improvement as soon as a week after medication. Your feline may experience flare-ups after the infection has cleared up. Talk to your vet about how to stay on top of treatment if this happens. 

If your cat has to have an apocrine cyst removed, it could take them a few days before they feel like themselves after the anesthesia. Lentigo in cats has no recovery period.