Canine non-inflammatory alopecia: What's new and what's old

Canine non-inflammatory alopecia: What's new and what's old

Jul 01, 2004

Photo 1: With ischemic dermatopathy, lesions can be encountered around the eyes. Visual scarring is apparent with an active disease.
I believe non-inflammatory alopecia in the dog is relatively common and can also be very frustrating. It must be differentiated from self-trauma and infectious causes. I am hoping this article will aid in clarification of some the conditions that cause non-inflammatory hair loss, and can help you make a proper diagnosis and reasonable treatment protocol.

We will exclude hypothyroidism and hyperadrenocorticism from our discussion, as these two endocrinopathies are fairly straightforward and not difficult to diagnose. I will mention, however, that Cushing's disease is a fairly common cause of alopecia (or even post-clipping alopecia, which I will elaborate later), but canine hypothyroidism associated with alopecia is much less commonly seen.

Photo 2: While fairly uncommon, localized rabies vaccine-induced ischemic dermatopathy still affects small breed dogs.
Ischemic dermatopathy This is a fairly well-recognized skin disease that includes several subtypes. The classical and originally described form is dermatomyositis (DM). This disease is genetically-based, immunologically mediated, and is seen almost exclusively in Shetland Sheepdogs and Collie breeds. The mode of transmission is autosomal dominant, with variable expression. It can occur at an early age in multiple members of a litter, or can be seen later in life as adult-onset type. Focal to more generalized alopecia with crusts, vesicles (rarely seen), erosions and ulcers on the face, around the eyes, pinnal margins, boney prominences, pressure point areas, and the tip of the tail are common locations for lesions (Photo 1). Many lesions are deep and focal scarring is not uncommon. It is also common to visualize scarring in areas of active disease. The muscle involvement usually is very mild and non-clinical. However, it can be severe especially in puppies and involve muscle atrophy, weakness and even mega-esophagus. The diagnosis is based upon results of skin histopathology, EMG's and muscle biopsies.

The treatment can include pentoxifylline, vitamin E, prednisone, azathioprine or cyclosporine. The cause is unknown, although certain investigators believe vaccine administration is implicated in the onset of skin lesions.

Photo 3: With pattern baldness hair starts to thin predominantly on the pre-auricular areas.
Localized rabies vaccine-induced ischemic dermatopathy is seen in certain small breed dogs (terriers, Bichons and poodles). It is fairly uncommon but occurs with some regularity in my practice (Photo 2). A patch of alopecia, with some hyperpigmentation and some crusts can be seen at the site of rabies vaccine administration (usually between the shoulder blades) one to six months after the vaccine was given. The lesion may resolve with or without scarring, may progress and enlarge or may progress to involve multifocal areas (the third subtype) on the entire body thus mimicking dermatomyositis. Diagnosis is made as in DM, and treatment may involve similar drug therapies as DM or may involve surgical removal (may be very difficult) and can also include cessation of vaccinations.

Photo 4: Pattern baldness can begin as early as 6 months of age in some cases.
Pattern baldness This is a fairly common skin condition that is considered to be completely cosmetic in nature. It is seen most often in Whippets, Greyhounds, Daschund, Boston terriers, Chihuahuas, and other small breed dogs. Hair begins to thin as early as six months of age, predominantly on the pre-auricular areas, head, ventral neck, chest and caudal thighs (Photos 3 and 4). It can be progressive and look striking, involving other locations until all areas become confluent, especially in older Daschunds. Some of the areas of alopecia can become hyperpigmented. Diagnosis is based upon clinical examination and/or results of skin histopathology. There is no recommended treatment. However, melatonin has shown some benefit in some cases.