Introduction
“Black Skin Disease” is a phrase used to refer to a form of hair loss (alopecia) in dogs that is influenced by hormones. The term more commonly used by veterinarians and breeders for this condition is “Alopecia X”. Other names include Growth Hormone Responsive Alopecia, Adult Onset Growth Hormone Deficiency, Growth Hormone Responsive Alopecia, Castration Responsive Alopecia, The Cold Funk, Coat Funk, Follicular Dysplasia, Post-clipping Alopecia, Wooly Coat Syndrome, Adrenal Sex Hormone Alopecia and Adrenal Hyperplasia-Like Syndrome. A newer term is Hair Cycle Arrest, although Alopecia X is the current preferred name for this condition, especially among veterinary dermatologists.
Little is known about this condition and its cause or causes. The most common signs of Alopecia X in dogs are extreme and symmetrical hair loss followed by hyperpigmentation, or darkening, of the skin. The hair loss can be so extreme that this condition is also known as SHL, or Severe Hair Loss.
Symptoms of Alopecia X - Black Skin Disease in Dogs
Alopecia X affects both male and female dogs, regardless of their spay/neuter status, although males may be more commonly affected . Dogs with Alopecia X usually have normal coats as puppies. They begin to develop signs of hyperpigmentation and hair loss in adolescence to early adulthood (in most cases by three years of age), although signs may start as early as one year and as late as ten years of age. Certain breeds are overrepresented, particularly Nordic breeds including the Pomeranian, Chow Chow, Alaskan Malamute, Siberian Husky, and Elkhound, among others. Toy and Miniature Poodles are also overrepresented. All coat colors seem to be equally affected.
Alopecia X is a form of patterned baldness, which means that it is symmetrical. Hair loss generally begins with the loss of long primary hairs (also called “guard hairs”), leaving the soft, fuzzy secondary hairs underneath. This is referred to as a “puppy coat,” and suggests why Alopecia X is sometimes referred to as “wooly coat syndrome”. Hair loss frequently is preceded by loss of color and lushness in the coat (presumably from a loss of melatonin). The coat becomes dry and “cottony”. Most dogs start with symmetrical, gradual thinning of hair on the back of their hind legs/thighs and along the top of their backs. Hair loss also occurs commonly under the tail, on the belly and around the genitals. With time, even the soft puppy-like coat falls out, and the skin is left bald. The hairless areas tend to spread, but normally are not itchy or painful and are not prone to infection. In extreme cases, hair loss can progress until fur is only present on the dog’s head and paws.
Hyperpigmentation of the skin normally follows the hair loss in blotchy patches along the back and hind legs, but in some cases the skin darkens more widely. The darkening may appear as small flecks of black skin, or the skin may become black solidly. Some dogs will never re-grow their coat. Others may re-grow their fur partially or temporarily. If re-growth occurs, the blackened skin usually peels away, exposing normal-looking skin.
No generalized (systemic) signs are associated with Alopecia X. If your dog has hair loss and also shows changes in appetite or thirst (increased or decreased eating or drinking), acts depressed or shows other signs of systemic illness, there probably is another underlying cause of the alopecia. Many other conditions can be confused with Alopecia X, and there currently is no medical test that can definitively diagnose this condition. Your veterinarian must rule out a number of other problems, particularly including hypothyroidism and Cushing’s disease, infection and inflammatory disease of the sebaceous glands, before arriving at a diagnosis of Alopecia X – which again is a symmetrical baldness of unknown origin.
Implications of Alopecia X - Black Skin Disease
Alopecia X does not appear to affect a dog’s health. The signs of Alopecia X – particularly hair loss and darkened skin – are primarily cosmetic issues. It may be that Alopecia X is not a single disease but instead a combination of several, making treatment decisions more difficult. Stress can exacerbate the signs of Alopecia X in dogs, and castration, diet changes or other hormonal or endocrine treatments may help to reduce the effects of stress and thereby reduce the hair loss and pigmentation associated with this condition.