Symptoms of Black Skin Disease
“Black skin disease” is a phrase used to refer to a form of hair loss (alopecia) in dogs that seems to be caused or at least influenced by hormonal imbalances. The term more commonly used by veterinarians and breeders for this condition is Alopecia X. Affected dogs typically have normal hair coats as puppies. They begin to develop signs of hair loss and hyperpigmentation (darkened skin) in adolescence to early adulthood, usually by three years of age, although signs may appear at any time. Dogs with this disorder lose their long, outer “guard” hairs first. Most cases start with gradual thinning of hair on the back of the hind legs and along the top of the back. Hair loss also occurs commonly under the tail, on the belly and around the genitals. The soft, fuzzy secondary coat becomes exposed. This is referred to as a “puppy coat” and suggests why Alopecia X is sometimes referred to as “wooly coat syndrome.” Over time, even the puppy-coat falls out, leaving the skin bald. The hairless areas tend to spread but normally are not itchy, painful or prone to infection. Darkening of the skin generally follows the hair loss. Some dogs never re-grow their coats; if they do, the hyperpigmented skin usually peels away, exposing fairly normal-looking skin underneath.
Alopecia X is a progressive condition that typically follows a reliable course. This includes:
- Gradual loss of color and lushness of the coat (presumably from a loss of melatonin)
- Gradual and symmetrical loss of outer guard hairs
- Increasingly dry, “cottony” undercoat
- Symmetrical baldness
- Hyperpigmentation of the skin
In extreme cases, hair loss can progress until fur is only present on the dog’s head and paws. Normally, the skin discoloration follows the hair loss in patches beginning along the back and hind legs, but in some cases the skin darkens more broadly. The darkening may appear as small flecks of black skin, or the skin may become solid black. Some dogs will re-grow their coat partially or temporarily. No generalized signs of illness 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.
Dogs At Increased Risk
Alopecia X has been diagnosed in dogs of all ages and breeds, regardless of their spay/neuter status. However, it seems to occur in males and in certain breeds more frequently than others. Nordic breeds are overrepresented, 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.