Alopecia X in Dogs

What is alopecia X?

Alopecia X is a skin condition that affects certain dog breeds. It causes symmetrical hair loss (alopecia), meaning that hair is lost in a similar pattern on both sides of the neck and body. The skin in the affected areas often becomes darker.

Alopecia X is not painful, and affected dogs are usually not itchy. The pattern of hair loss resembles that caused by endocrine (hormonal) conditions, such as hypothyroidism and Cushing’s disease (hyperadrenocorticism). However, the condition is poorly understood, which is why it is called alopecia “X.”

Because its cause is uncertain, alopecia X has been described by several other names, including:

• Black skin disease
• Coat funk
• Adrenal sex hormone alopecia
• Hair cycle arrest
• Castration-responsive alopecia
• Growth hormone-responsive alopecia
• Follicular dysplasia of Siberian Huskies
• Pseudo-Cushing’s syndrome

What are the signs of alopecia X?

Affected dogs first start to lose their guard hairs, which form the outer layer of the coat. The remaining coat may become dull, dry, or fuzzy and may change color. Hair loss then develops on the flanks and in areas subject to friction. It may eventually spread over the neck, trunk, tail, and thighs. The head and lower legs are typically spared and retain their hair. The skin in affected areas becomes darker.

Alopecia X itself does not usually cause inflammation or discomfort and is mainly a cosmetic condition. It is not contagious to other dogs. Although affected dogs are generally not bothered by the hair loss, their appearance may concern their owners.

What causes alopecia X?

The exact cause of alopecia X is unknown. Sex hormones such as estrogen, testosterone, and progesterone, or their precursors (naturally occurring substances the body uses to make these hormones) may play a role. However, this relationship has not been proven. Hormone metabolism may be altered, or the hair follicles may not respond normally to hormonal signals. Growth hormone deficiency later in life has also been proposed as a possible factor.

Which dogs are most commonly affected?

This disorder typically begins in young adulthood. Commonly affected dogs include Poodles and several Nordic or plush-coated breeds, such as:

• Alaskan Malamute
• American Eskimo Dog
• Chow Chow
• Keeshond
• Pomeranian
• Samoyed
• Schipperkee
• Siberian Husky

Alopecia X can affect both male and female dogs, whether they are intact, spayed, or neutered. However, some reports suggest that intact male dogs may be affected more often.

How is alopecia X diagnosed?

Your veterinarian may suspect alopecia X based on the characteristic pattern of hair loss, your dog’s age, and their breed. However, alopecia X is a diagnosis of exclusion, which means that your veterinarian must rule out other causes of hair loss, especially other hormonal disorders that produce a similar pattern. Recommended tests may include:

• Baseline testing. A complete blood count (CBC), serum biochemistry, and urinalysis help assess your dog’s overall health and organ function.
• Thyroid hormone testing. These blood tests help rule out hypothyroidism (underactive thyroid gland).
• Testing for Cushing’s disease. Adrenal function testing may be used to rule out Cushing’s disease (hyperadrenocorticism), in which the body produces too much cortisol.
• Skin cytology. Samples of skin cells are examined under a microscope to look for bacterial or yeast infections.
• Skin scrapings. Samples scraped from the skin are examined for mites that cause mange. 

A skin biopsy may also be recommended. During this procedure, the veterinarian removes a small sample of skin for examination by a veterinary pathologist. The hair follicles may have changes consistent with alopecia X, and the biopsy can help rule out inflammatory and other skin diseases. However, biopsy findings cannot confirm alopecia X by themselves.

Adrenal sex hormone panels are available through some specialized laboratories. This testing is costly and difficult to interpret because unaffected dogs can also have abnormal hormone levels. However, it may help direct treatment if specific abnormalities are found.

Can alopecia X be treated?

Several treatments may stimulate hair regrowth, but no treatment works for every dog. Even after successful treatment, the hair loss may eventually return. Your veterinarian will help you weigh the possible benefits of treatment against its risks.

Spaying or neutering is the first step. Many dogs will regrow hair, although the alopecia may recur years later.

Melatonin is a hormone that helps regulate the sleep–wake cycle and may also influence sex hormones and hair follicles. It may stimulate hair regrowth in 40% to 60% of dogs. It is relatively inexpensive and generally safe, although sedation can be a side effect. It should not be used in patients that are diabetic. Melatonin is a human over-the-counter supplement, so be careful to avoid formulations with xylitol, an artificial sweetener that is toxic to dogs. 

Deslorelin is an implanted medication that reduces the production of reproductive hormones, such as testosterone and estrogen. It may stimulate hair regrowth in some intact male dogs. It is generally avoided in intact female dogs and evidence supporting its use in spayed or neutered dogs is limited. Your veterinarian will determine whether it is appropriate for your dog.

Microneedling is a dermatological procedure that creates many small, controlled punctures in the skin to stimulate hair regrowth. Because the procedure can be painful, appropriate anesthesia and pain control are needed. The possible benefits and risks should be carefully considered when treating a cosmetic condition.

Trilostane and mitotane are medications used to treat Cushing’s disease. These drugs suppress cortisol hormone production by the adrenal glands and can also suppress sex hormone production. However, they can cause more serious side effects and require frequent blood tests to monitor adrenal function.

Long-acting progesterone injections such as medroxyprogesterone acetate may stimulate hair regrowth in some dogs, but risks include tumors in the mammary glands and diabetes. Dogs receiving this treatment require careful monitoring.

Will my dog's hair grow back?

Your dog’s hair may grow back. Without treatment, hair regrowth is unlikely, although spontaneous regrowth can sometimes occur. Hair that regrows following treatment may later be lost again.

Some treatments are costly and can cause significant side effects, so their use for a cosmetic condition must be considered carefully. If your dog does not respond to simpler options, such as spaying or neutering, when appropriate, or melatonin, you may choose to monitor the condition without pursuing further treatment. Alopecia X itself is not expected to shorten your dog’s lifespan.