Alopecia is the complete or partial loss of hair or failure to grow hair. Pets can be born with alopecia or it can develop over time. It can occur in one area, multiple areas or over the entire body. Patterns of alopecia range from a single area of missing hair to multiple randomly occurring areas to a symmetrical pattern. Most cases of alopecia do not cause discomfort, but they can be a symptom of a larger underlying problem.
Certain breeds of dogs have a genetic predisposition to certain types of primary alopecia. Doberman pinschers can have a disorder called color dilution alopecia where the areas of their coat that are lighter in pigment lose hair. Boxers, bulldogs and Airedale terriers can have a disorder called seasonal flank alopecia where hair loss occurs on the flanks between November and March each year. Thick or “plush” coated breeds such as Pomeranians, chow chows, keeshonds, Samoyeds, Siberian huskies, Alaskan malamutes and miniature poodles are more prone to an adrenal gland sex hormone disorder called alopecia X.
Dermatophytosis, aka ringworm, is an infectious disorder caused by a fungus, most commonly seen in young animals. Ringworm tends to appear as a patchy alopecia. Skin yeast or bacterial infections can also appear as patchy alopecia, as well as infections from certain mites.
Hormonal diseases such as hypothyroidism, hyperadrenocorticism (Cushing’s disease) or a specific type of tumor called a Sertoli cell tumor can all have alopecia as a secondary external sign of disease. With these hormone-driven alopecias, the pattern of alopecia is bilaterally symmetrical.
Depending on the underlying cause of the alopecia, the symptoms a pet has may vary. For the genetic forms of alopecia, the typical presentation is solely the hair loss. Infectious forms of alopecia often present with itching and perhaps redness or scaling of the skin. Alopecia caused by hypothyroidism may be associated with low energy levels and unexpected weight gain. Hyperadrenocorticism often presents with hair loss and excessive drinking, excessive urination, increased appetite and muscle atrophy. Dogs with Sertoli cell tumors can show signs of feminization such as mammary gland development.
Diagnosing what type of alopecia a pet has may require a physical exam, an examination of the pet’s history and blood and skin testing, including a skin biopsy.
The underlying cause of hair loss or lack of hair growth dictates the treatment. Genetic forms of alopecia may not need to be treated, since they tend to be more of a cosmetic than overall health problem. Melatonin has been used to treat seasonal flank alopecia. Neutering (spaying or castration) has been shown to improve the growth of hair in many dogs with alopecia X.
Infectious causes of alopecia each carry with them a specific treatment. Most cases are treatable but often require many weeks of therapy to resolve the disease completely.
Hormonal diseases causing alopecia can be difficult to diagnose and often require lifelong therapy to prevent symptoms from returning.
Alopecia is a relatively common problem seen in the pet dog population. In some cases the diagnosis and treatment is straightforward. In other cases, enlisting the help of a veterinary dermatologist is essential to secure an accurate diagnosis and formulate an effective treatment plan.
Erik Melin is a veterinarian at Westgate Pet Clinic in Linden Hills. Email general pet questions to firstname.lastname@example.org. Veterinarians cannot give pet-specific medical advice without an office visit.