Malassezia dermatitis: Is it complicating your life?

Malassezia (yeast) dermatitis can result in a primary skin problem orbe present secondary to underlying disease. Because its presence can mimic(and complicate) other diseases such as atopy and food allergy, it is importantto know how to recognize the organism, and of course, treat for it.

Malassezia pachydermatis (Pityrosporum) is a lipid-loving, normal inhabitantof canine and feline skin residing in the ear canals, rectum/anal sacs andvagina. It was first described as a disease in humans (seborrheic dermatitis)in 1847 by Malassez. The commensal yeast organism becomes a problem dueto excessive sebum production (Malassezia loves lipids), heat, humidity,bacteria or inflammation. Underlying allergy or endocrine disease i.e. hypothyroidismcan predispose to yeast infection. Enhanced yeast growth can occur whenStaphylococcus spp. are present. New studies indicate that yeast is presentin greater amounts in atopics with a yeast hypersensitivity state possible.Inflammation may occur because of lipases released by the yeast that liberatezymogen thereby activating complement.

No discrimination

Malassezia dermatitis can affect any age, breed, or gender of dog butsome breeds appear to be predisposed including the Shih Tzu, Lhasa Apso,Cocker Spaniel, Jack Russell Terrier, Poodle, West Highland White Terrier,Shetland Sheepdog, Labrador Retriever, Chihuahua, Maltese, Basset Hound,German Shepherd, Dachshund, Springer Spaniel and Golden Retriever. Clinicalfindings include pruritus, odor, seborrhea oleosa, yellow or gray scaling,erythema and lichenification.

Areas of the body affected include skin folds such as the ventral neck,axillae, groin, umbilical fold, nailbeds, perineum, muzzle and ears. Somecanine patients experience intense facial/muzzle pruritus almost to thepoint of the owners believing the patient is having a seizure. Other caninepatients with a generalized yeast dermatitis seem depressed, with improvementin activity/attitude after treatment.

Malassezia dermatitis/otitis does not appear to be as common in cats,but generalized cases have been reported. Yeast has been recognized in felineacne and also associated with a black, waxy otitis externa. Recurrent generalizedMalassezia in cats has been associated with FIV infection.

Some reports indicate that 50 percent of the time, Malassezia dermatitisin dogs can be associated with underlying allergy. Hypersensitivity reactionsto Malassezia have been documented in humans and there is reason to believethat this may be true in dogs as well.

Diagnosis

The quickest and easiest way to diagnose Malassezia is by cytology.

Impression smears are made using a microscope slide pressed against theskin, or a surgical blade or a swab of the skin using a cotton-tipped swab.The slide is heat fixed then stained with Diff-Quik, Gram Stain, or MethyleneBlue and observed under oil immersion. Malassezia appears as round or ovalbudding yeast-like cells 3-8um in diameter staining dark blue. They areeither single, clumped, or adhered to keratinocytes. Normal numbers of yeastvary between 3-6/hpf. Cultures are usually not necessary but if desired,Sabouraud's dextrose agar is used. It may be helpful to add oil to the culturemedium as yeast are lipid-loving and oil will encourage their growth. Histopathologyoccasionally reveals yeast in the upper layers of the epidermis but theycan easily be washed off in the sample preparation process. When yeast areobserved in hair follicles, be suspicious of possible pathogenicity. Insome cases, the diagnosis of Malassezia dermatitis depends upon the responseto therapy.

Treatment

Systemic therapy for Malassezia dermatitis involves antifungals suchas ketoconazole, itraconazole, or fluconazole. Griseofulvin has no activityagainst Malassezia. Ketoconazole (Nizoral) 2.5-5mg/kg bid orally for twoto four weeks is the usual drug of choice.

Some patients may need a low maintenance dose to keep them under control.Potential side effects include anorexia, vomiting, diarrhea, and lethargy.Ketoconazole can lower cortisol levels in some patients and the additionof prednisone 0.l mg/lb sid may be necessary.

Antifungals can also be teratogenic and lower testosterone levels. Ketoconazolecan elevate liver enzymes in humans so it is advisable to monitor serumprofiles in canine and feline patients on ketoconazole (and the other azoles)longer than two months. Itraconazole (Sporanox) is dosed at 5mg/kg/day orally.It is more expensive than ketoconazole yet does not tend to cause as manygastrointestinal side effects. It may cause less vomiting in cats comparedto ketoconazole, however some cats have developed hepatotoxicity. Fluconazole(Diflucan) has been used in dogs at 2.5-5mg/kg/day orally.

It may be advisable in some patients to treat initially with antibacterialscombined with antiyeast medication as most often Staph bacterial infectionsaccompany Malassezia dermatitis.

Topical therapies include shampoos such as Nizoral shampoo, Sebahex,Malaseb, Miconazole, Dermazole, benzoyl peroxides, chlorhexidine-at least2 percent, selenium sulfide, tar (not in cats), iodine or lime sulfur. Shampoosfollowed by a leave-on rinse with antiyeast activity such as Resichlor ora 50:50 vinegar/water mixture may provide a more lasting effect.

Underlying culprit

Remember to check for underlying disease as the cause of the Malasseziaproblem. Atopy, food allergy, endocrine disorders, demodicosis, and bacterialpyoderma can be accompanied by Malassezia. Finally, there have been tworeports of Malassezia being "contagious" to other animals andhumans.

One case occurred in a colony of laboratory Beagles, the other in a pediatricintensive care unit transferred by a nurse petting her dog and not washingher hands before handling patients.