Derm's dirty Dozen, The top chronic, recurrent cases destined to cause frustration

I have noticed that as the years go by, I have begun to feel more and more frustrated with certain skin cases (cats included) that are referred to me in my practice in San Francisco and the surrounding Bay Area.

Carlo Vitale, DVM, ACVD.

I don't see any differences geographically with the types of cases in my three practices in San Francisco, San Leandro or Walnut Creek. These cases follow me everywhere.

I have been in private practice for seven years and sense a growing number of cases (or is it just cumulative?) that are on my dirty dozen list.

During recent years, there has been an explosion in the numbers of cases seen daily with very concerned and frustrated owners with pets plagued with very unusual and/or recurrent diseases to treat and manage. I don't recall the existence of these cases as a dermatology resident at the University of California-Davis Veterinary Teaching Hospital (UC-Davis) under the legendary Dr. Peter Irhke. Maybe I was just too naive and actually thought I could cure all.

This month, we will look a little closer at the top dermatological problems that plague your patients.

• Disease 1:

Canine recurrent superficial pyoderma

I wrote an article recently in

DVM Newsmagazine

concerning this very same topic, so I won't go into too much detail. But this disease is so frustrating that it deserves repeating! I would have to say it also is the most-common case that is referred to me.

First of all, this disease is essentially, an immunologic dysfunction. Staphylococcus intermedius is a resident inhabitant of the normal skin, ear canal, anal sac and dog hairs. They actually live on the skin and hair in normal, healthy dogs. The problem is that some dogs are not normal, they develop pyoderma. Superficial pyoderma manifest usually in the glabrous skin (axillae and groin) or trunk. It spares the face and limbs for the most part. We all know what it can look like: papules that evolve into pustules, epidermal collarettes, or simply redness and alopecia (surface pyoderma). It tends to start early in age (first few years of life), occur in Retrievers, many small breeds such as Terriers (except Border Terriers) and Pit Bulls. Pruritus may be severe or absent. Often an odor accompanies the pyoderma.

Treatment includes anti-staphylococcal antibiotics for at least 21 days such as potentiated sulfa-type antibiotics, cephalexin or fluoroquinolones. I often recommend twice-weekly shampoo therapy with benzoyl peroxide-containing shampoos, chlorhexidine-based or ethyl lactate-based shampoos. We know now that certain dogs with recurrent pyoderma have a higher carriage of cocci on the skin even when the dog appears clinically normal, and these cocci tend to adhere more strongly to corneocytes. So, it makes sense to bathe frequently even when the patient appears normal.

Here is the difficult part: The pyoderma returns after treatment. I believe that the most common reason is still due to flea allergy. A very close second is atopic dermatitis (which is next on the list). Food allergy, primary seborrhea (as described in the Cocker Spaniel) and demodex are distant thirds. A complete work-up also may include thyroid function measurement or an ACTH stimulation test to search for endocrinopathies that are also incriminated in recurrent pyoderma in the dog.

After the treatment and diagnostic plan addressing these possible underlying causes reveals normal findings, you will be left with primary or idiopathic pyoderma.

Dogs presented with superficial pyoderma primarily have lesions confined to the trunk. The most common lesions identified included papules and pustules.

These cases are treated similarly as the others, but you may include so-called pulse therapy, which actually is a misnomer. You may offer antibiotics for long-term treatment by administering antibiotics several days of the week on and the remaining days of the week off. I also recommend using staphage lysate at 0.5cc subcutaneously twice weekly.

• Disease 2:

Atopic dermatitis

We could nickname this one the itch that won't go away! This condition is indeed very difficult to manage and equally frustrating. I will not go deep into the immunologic dysfunction of this condition, but it's worth repeating the fact that atopic dogs have a higher carriage of cocci with stronger adherence factors to epidermal corneocytes. This leads, in part, to recurrent pyoderma as previously described. They also are pruritic, so self-trauma potentiates pyoderma. These dogs start to manifest symptoms of pruritus less than 3 years of age (as early as 3-4 months) and can be affected seasonally or non-seasonally. Facial or pedal involvement is very common, as well as axillary pruritus, perianal pruritus, otic disease and groin involvement.

Some candies prove toxic for dogs

The main issue with atopic dermatitis is itch. Owners complain that this symptom is their biggest concern. Here is our job to help relieve the dog's pruritus and make everyone happy. I don't believe in long-term corticosteroid administration but the reality is, many cases respond only to this type of therapy. In mild to moderate cases, I strong advise antihistamine therapy accompanied by fatty acids given orally. The fatty acids should be comprised of omega-6 and omega-3 fatty acids in a 5:1 ratio, respectively. This type of therapy should be given for at least three to four weeks to evaluate effectiveness. I prefer diphenhydramine or hydroxyzine for antihistamine therapy. It is clear that the newer generation antihistamines, such as loraditine or cetirizine, are ineffective for the management of pruritus.

Topical therapy also can be prescribed with or without the antihistamine/fatty acid treatment and can include oatmeal shampoo with or without a topical anesthetic, witch hazel sprays, epidermal lipid-replacement therapy and corticosteroid-containing sprays. Recently, a new topical, low-potency corticosteroid spray has been introduced and appears to be very effective.

Concerns about iatrogenic Cushing's disease (at the site of repeated spraying) warrants close monitoring patients. Comedones (cream-colored or black), thinning skin and bruising are all warnings that corticosteroid therapy must cease. If oral corticosteroid therapy is administered for long-term therapy, I advise performing a urinalysis and aerobic culture (do not rely on the lab for culture, ask for it initially). About 20 percent of cases will have occult urinary tract infection.

Recently, modified cyclosporine has been approved for use in the dog. It has been available for many years for treatment of human diseases, so veterinary patients have benefited from this drug since 1995. This drug is an immunosuppressant, therefore careful patient selection and monitoring are in order when prescribing this drug. The drug suppresses non-stimulated T-cells, so its use in human patients extends to immune-mediated diseases, as well as the prevention of transplantation rejection. Feline patients have been prescribed this drug for the prevention of kidney transplant rejection as well. The dosage is 5mg/kg/day for atopic dermatitis and should be given on an empty stomach. It can take one to two weeks to take effect. The most common side effect is nausea and vomiting which, if mild to moderate, can be treated with famotidine one hour prior to administration.

Given with a full stomach can diminish absorption, so it is advised to administer cyclosporine one hour prior or two hours after a meal. This drug can be used for short to intermediate lengths of time. The long-term effects (greater than three years) has not been evaluated. It might be advisable in some cases to monitor kidney and liver functions, as well as cyclosporine plasma levels due to the unusual occurrence of toxicity at that dosage.

• Disease 3:

Hyperplastic otitis externa/media

I shiver when a Cocker Spaniel walks into my examination room and the owner complains of a "chronic ear infection".Why? These cases are extremely frustrating and often result in failure, especially when it involves

Pseudomonas

. The most important thing to remember is the hyperplasia resulting from the inflammation and infection can perpetuate the problem. Hyperplasia of the epidermal glands can accompany the primary otitis and make matters worse.

The causes of otitis (especially in the Cocker Spaniel) are many and usually include anatomy, allergy, hypothyroidism and primary seborrhea. These underlying causes can initiate the infection, but the resulting hyperplasia and microbial overgrowth perpetuate it.

The first thing to do is to take a thorough history and perform a good examination. An examination includes performing otoscopy and evaluating the integrity of the tympanum membrane (TM). Once the TM is ruptured, otitis media is diagnosed. Cytological evaluation of the otic exudation is crucial. This may involve obtaining a sample from deep in the vertical canal or middle ear. I base prognosis and treatment upon many things, including the results of otic exudate cytology. Any cytology demonstrating rods should be cultured (aerobic culture and sensitivity).

Treatment includes corticosteroids administered orally and topically if hyperplasia is moderate to severe. Pending results of culture and if numerous rods are visualized upon cytology, I prescribe either aminogylcosides or fluoroquinolones-containing otic preparations with corticosteroids (when hyperplasia is evident). Besides the readily available topical fluoroquinolone or aminoglycoside-containing otic preparations, the following recipes can aid in the treatment of refractory gram-negative or Pseudomonal otitis.

• Amikacin otic: 15 cc Amikacin (injectable amikacin 50mg/ml) mixed with 15 cc sterile water.

• Prepared ophthalmic drops (neomycin/-polymyxin/gramicidin) used as an otic product with or without dexamethasone.

• Prepared ophthalmic drops containing tobramycin with or without dexamethsone.

Pseudomonas is uncommonly cultured from cases of chronic otitis and can be difficult to treat. Treatment can include the above topical otic preparations but always should include appropriate oral antibiotics (choice based upon culture and sensitivity). These can include the fluoroquinolones (enrofloxacin and ciprofloxacin) at dosages of 20 mg/kg/day or marbofloxacin at 2 mg to 5 mg/kg/day. Most often, cases of otitis externa are treated for three to four weeks, and otitis media are treated for four to eight weeks. Unfortunately, if medical management fails, surgery (total ear ablation with or without bulla osteotomy) is advised.

• Disease 4:

Eosinophilic granuloma in the cat

Apparently in the cat, studies have shown that early-age onset cases tend be genetically based and not curable. I found this to be true. Cases that start later in life can be allergic in origin and curable.

Eosinophilic granuloma manifests in several forms. The classic presentation is the so-called rodent or indolent ulcer. This ulcer (which is usually accompanied by swelling) occurs on the upper lip unilaterally or bilaterally and can be confluent. Most cats are unaffected by this ulcer and seem to go about life without any problem. My opinion is that Main Coon cats, the Siamese breeds and other exotic breeds are predisposed early in age with onset of disease. The so-called granuloma also can involve the trunk, paw pads or the caudal thighs (linear granuloma). Some of these cats effected with haired-skin granuloma are pruritic.

In the late age of onset cases (and even in a few of the early age in onset cases), it is worth pursing underlying allergy as a primary cause. My opinion is flea allergy is the most-common cause of these eruptions. Atopic dermatitis and food allergy are two very uncommon causes of indolent ulceration and eosinophilic granuloma formation.

Treatment can include oral and injectable corticosteroids. Luckily, feline patients tolerate corticosteroids well, so I usually prescribe either oral triamcinolone or dexamethasone. I prefer oral corticosteroids, as the injectable forms are unpredictable in the onset of effect and duration. I also specifically prefer oral triamcinolone, as dexamethasone can cause diarrhea. Dosages of triamcinolone are similar for most average 5 kg cats. Tapering dosages of 0.75 mg twice daily are usually sufficient over two to three weeks to resolve most cases. Occasionally, bacterial colonization occurs (especially on the lip) and antibiotics can help or even resolve these lesions. Cyclosporine at 5mg/kg/day has been used as alternatives to corticosteroids. I have also used injectable gold and chlorambucil therapy in the treatment of refractory cases of eosinophilic granuloma in the cat with some success.

• Disease 5:

Facial Pemphigus foliaceus (PF) in the Chow Chow/Akita

This form of pemphigus can be very refractory to treat and is likely a different entity to the naturally occurring truncal pemphigus in other breeds. This form of PF is probably a bit deeper in the dermis histologically than the routine cases of PF. The immunologic mechanism involve antibodies produced against the intercellular substance that "holds" the epidermal skin cells together, thus resulting in dissolution of the cell-to-cell cohesion.

As a result, the canine immune system recruits neutrophils to repair and fill the void in the "space" that has been created by the epidermal cell-to-cell dissolution. This quickly results in a very large pustule (neutrophil-laden, by definition) that spans multiple hair follicles and clinically presents in large crusts due to the fragile and transient nature of the pustules. Most of these pustules occur on the face, paw pads, trunk, nipples and limbs.

Cytology and biopsy are techniques to make a definitive diagnosis. I have occasionally based treatment on a diagnosis solely from cytology, but I would advise against this technique in private practice.

Once diagnosis is made, the treatment focuses on immunosuppression and includes oral corticosteroids and other agents. Prednisone at 2-4mg/kg/day accompanied by azathioprine or chlorambucil is highly recommended. It seems that most dogs with PF are affected long-term, so it therefore seems advisable to incorporate alternative therapies to corticosteroids early on in treatment. Other single-agent therapies include oral cyclosporine (5-20 mg/kg/day). Alternatives to these therapies also include oral tetracycline and niacinamide. Dogs greater than 20 kg are administered 500 mg tetracycline and niacinamide every eight hours, and dogs less than 20 kg are given 250 mg of these two drugs every eight hours. These drugs are immunomodulatory and can aid in the treatment of immune-mediated skin diseases. Lastly, injectable gold therapy can also be considered as a single agent.

• Disease 6:

Feline cutaneous herpes infection

Since the discovery of cutaneous feline herpes infection several years ago, it has been clear that this disease can be chronic. Herpes infection in the cat involves mainly the haired skin of the face but can involve the planum nasale, too. Some cases are preceded by several months or years of upper respiratory symptoms, including episodic sneezing and conjunctivitis. Most of the cases of cutaneous feline herpes infection occur during adulthood. In fact, many cases occur in older cats greater than 5 years of age. After this initial upper respiratory disease, the owner notices lesions on the planum or more likely haired skin of the muzzle. These lesions usually are ulcerated and very crusted. Cytology and histology can reveal primarily eosinophils and some neutrophils, and can mimic eosinophilic granuloma clinically and more likely, histologically. Diagnosis is based upon clinical examination and usually results of histopathology. Often epidermal inclusions bodies of the herpes virus are seen, but not always.

Treatment has included oral lysine, oral interferon, topical and oral acyclovir, and more recently, oral Famvir. Famvir is the trade name of an oral anti-herpes medication for humans, and I have found it to be very helpful and safe in cats. The dosage is 125 mg (one-half of a 250 mg tablet) every eight hours. It costs about $175-200 for a three-week supply. I have not found the other therapies to be of benefit. Famvir is usually administered for at least three to four weeks. The disease is often chronic, and relapses are very common.

Editor’s Note: Next month Dr. Vitale will round out the other six worst cases in Derm’s dirty dozen.