Generally, baldness is not considered to be a major problem with dogs. It tends to affect a relatively small percentage of the population, and even then is usually only considered a major defect when it happens to animals that are active in the show ring. However, there are times when animal baldness should be taken more seriously, as it could very well be the sign of much more serious problems that are lying in wait.
Patterned baldness is an unpredictable disease. Victims usually are born with thick and normal coats as puppies, with bald spots only beginning to develop at the point of maturity. These bald spots first tend to appear on the flanks, inside the hind legs, and along the front and sides of the neck, often at the deepest part of the chest. It can be distinguished from other causes of hair loss by its distinctive pattern: hair loss as a result of patterned baldness will always occur symmetrically.
When hair loss is noticed, even if it's entirely symmetrical, there are many other potential causes that must first be ruled out before patterned baldness can be diagnosed. These include thyroid deficiencies, allergic reactions to food and medication, and infestations by parasites such as fleas, ticks, or mites. Blood samples and visual examinations are usually enough to confidently rule out these other causes, but depending on the results, your veterinarian might order still more tests just to make certain.
There's no real treatment for patterned baldness. Many ointments and shampoos can be found on the market, and while it shouldn't hurt to give them a try and the importance of regular grooming should never be understated, there's no conclusive evidence that any medicinal approach can effectively restore all or even most of a dog's coat once it is lost through patterned baldness.
That said, however, it remains very important to diagnose the disease accurately. Even if it can't be treated and isn't particularly serious in itself, patterned baldness is an autoimmune disease and thus can be very significant. Dogs that suffer from one autoimmune disease can easily be prone to another, and this can spell unheard of amounts of trouble for you and your animal if you're not prepared.
Possible complications from future autoimmune problems include an increased sensitivity to allergies and all the problems typically associated with that, problems with the reproductive system, pancreatitis in which the body's digestive enzymes begins attack healthy tissue, degenerative myelopathy in which antibodies attack nerve fibers in the central nervous system, and a variety of other skin disorders such as "hot spots". In extreme cases, it can even lead to severely stunted growth in larger breeds, with some animals that would typically weigh up to 100 pounds coming in full grown at under 40.
The method by which patterned baldness is inherited is largely unknown, but because of the implications it has for the potential for other diseases, breeding is generally not recommended.