Visiting Veterinarian : How to diagnose irritated or discolored noses on dogs
Nanki-poo is a handsome, middle-aged collie mix with a majestic jet-black coat. Until this fall, he also had a perfect, matching black nose. But in October Nanki-poo's nose began looking pale. Over time, it got paler and paler until it looked almost white. We're not talking about the hair on his muzzle, the way old dogs go grey with age, but his actual sniffer, technically called the nasal planum. "The texture seemed to change, too," his owner reported. "It was almost transparent, like you could see the blood vessels inside."
Eventually Nanki-poo's nose started to ulcerate, and became covered in thick scabs and ugly crusts. The condition resolved temporarily with symptomatic treatment but then rapidly recurred, and by the time she came to see me, the crusting was spreading up from the nasal planum along the top of his snout. "What's causing this?" his mom asked unhappily. I sighed. Diseases of the canine nasal planum. There are over a dozen that can all look very similar, and an equally long list of possible treatments. Without a biopsy, it's virtually impossible to make a definitive diagnosis. And without an accurate diagnosis, it's hard to choose the best therapy. I considered the possibilities.
Numerous disorders may simply cause a dog's nose to lose color. "Dudley nose" is a common syndrome affecting Siberian huskies, Labradors, and golden retrievers. Probably genetic in origin, it is caused by a lack of synthesis of the pigment melanin. Vitiligo is another depigmentation condition. It affects Rottweilers, and in addition to pale noses, may cause pigment loss around the lips and eyes. Another abnormality in melanin synthesis is a seasonal problem called "snow nose" in which the nose is darker in summer but pales in winter. It also affects Siberian huskies, Labradors, and golden retrievers, as well as Bernese mountain dogs. While all of these are fairly common, they usually are associated solely with a change in color, not with the severe crusting and thickening we were seeing on Nanki-poo's nose.
So what else should we consider? Straightforward trauma can result in nasal planum lesions, like if a dog roots around in something irritating or caustic, but that didn't fit with Nanki-poo's history of gradual onset and recurrence. Thickened, crusty noses can indicate idiopathic nasal hyperkeratosis, a condition of unknown cause primarily afflicting young Labradors, but Nanki-poo isn't a young lab, and he has extensive ulcerations, which rules this diagnosis out.
Sunlight exposure (specifically UV radiation) can cause dermatitis which is known to affect collies the most often (as well as border collies, Shelties, bull terriers, Dalmatians, and other dogs with light-colored faces). In fact, the prevalence of solar dermatitis in collies is so high, it is colloquially called "collie nose." Nanki-poo is a collie mix, so I wouldn't completely eliminate this diagnosis, but solar dermatitis usually occurs in summertime, and would be unlikely in a black-all-over dog like Nanki-poo.
The most likely diagnosis was certainly one of the autoimmune diseases. Discoid lupus erythematosus, pemphigus erythematosus, pemphigus foliaceous. In these diseases, the immune system gets confused and attacks various layers of Nanki-poo's own skin resulting in different combinations of depigmentation, ulceration, crusting, bleeding, thinning or thickening, and secondary bacterial infections. Another possibility was mucocutaneous pyoderma, a superficial toxic reaction that may include an auto-immune component triggered by bacteria. Only a biopsy could determine for sure if Nanki-poo had autoimmune disease and, if so, which one.
I examined Nanki-poo for other signs of illness that might help narrow down the diagnosis. We also had to consider the remote possibility of skin cancer, such as squamous cell carcinoma, or the rare inflammatory disorder, cutaneous histiocytosis, that affects collies and Shelties, and is sometimes referred to as "clown nose." Or it could be cutaneous vasculitis, epitheliotropic T cell lymphoma (also know as mycosis fungoides), zinc responsive dermatosis, mast cell cancer, a drug reaction, or even a weird presentation of the ringworm fungus. Any of these primary problems could then be complicated by secondary bacterial infection.
Since it's usually better to delay biopsy until any bacterial infection is resolved, we started Nanki-poo on long-term antibiotics. What else could we do? Avoid peak sun exposure and, once he is less raw, maybe apply child-safe sun screen to his nose. Try one of the many over-the-counter topical treatments that have been touted to help — Eucerin hand cream, vitamin E, Vaseline, Bag Balm. Applied frequently, these occasionally lead to dramatic improvement, but not always, and generally as soon as treatment is discontinued, the problem recurs. Nanki-poo's condition was so advanced I suggested skipping these OTC preparations, and instead trying a prescription antibacterial ointment called mupirocin.
Since we are highly suspicious of autoimmune disease, if Nanki-poo doesn't improve, there is another protocol to try next. Oral tetracycline and niacinamide. Also known as vitamin B-3, niacinamide has modulating effects on the immune system and combined with tetracycline is useful in controlling discoid lupus and pemphigus erythematosus in 25 to 65 percent of canine cases. It's a cumbersome process involving six pills every day for six to eight weeks and has some potential side effects, but if Plan A doesn't succeed, it's a pretty good Plan B. Sometimes oral prednisone, a corticosteroid, is added to this protocol. Systemic immunosuppressants like prednisone are often the cornerstone of treatment for autoimmune diseases, but long-term use can have side effects. Some veterinarians prescribe topical immunosuppressants instead, such as tacrolimus ointment, but this can be prohibitively expensive.
Nanki-poo went home with antibiotics, anti-bacterial ointment, and instructions for a recheck in two to three weeks. If it works, that's great, but these nasal planum diseases can be really pesky. A biopsy would be the ideal next step. Since the nose is very vascular and sensitive, general anesthesia is necessary, and multiple sites should be sampled. It may sound like a hassle, but basing our therapy on an accurate diagnosis rather than guessing is our best bet for getting Nanki-poo back his beautiful, smooth, black nose.