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616 Malassezia Dermatitis

• CBC, serum chemistry panel, and urinalysis for 2 consecutive days per week or given numbers disproportionate to the level of
pruritus experienced by the animal.
to screen for systemic internal diseases daily for cycles of 1 week on/1 to 4 weeks • Skin culture for Malassezia yeast is not
VetBooks.ir • Feline retroviral testing Drug Interactions recommended in clinical practice because
off after the initial induction dose (see Acute
• Hormonal testing (e.g., screening tests for
General Treatment above).
endocrinopathies)
these organisms are residents on the skin.
considered superior to cytologic evaluation
TREATMENT Azole therapy may alter the metabolism or • Biopsy with histopathologic evaluation is not
distribution of other prescribed medication for the diagnosis of Malassezia dermatitis
Treatment Overview by inhibiting cytochrome P450 metabolizing (most of the surface scale is lost during biopsy
The main goal is to reduce pruritus and remove enzymes and P-glycoprotein transporting processing) but may be useful in the diagnosis
seborrhea. This is accomplished by killing yeast pumps. Terbinafine does not inhibit these of primary skin disorders in which Malassezia
and controlling underlying primary diseases enzymes. Specifically, azoles cannot be given dermatitis is a secondary phenomenon.
and risk factors. with high-dose, extralabel macrocyclic lactones • Do not use selenium sulfide on cats; it is
(e.g., avermectins); if needed, dosage reduction too irritating to their skin.
Acute General Treatment and close monitoring are required. • Enilconazole is not approved for small-animal
• Keratomodulating (antiseborrheic) and anti- use in some countries.
yeast topical therapies (e.g., sulfur/salicylic Possible Complications • When given in tablet or capsule form, the
acid, phytosphingosine, ceramides, benzoyl • Idiosyncratic cutaneous adverse reactions to azole drugs ketoconazole and itraconazole are
peroxide, selenium sulfide, boric/acetic topical therapies best absorbed systemically if administered
acid, miconazole, clotrimazole, climbazole, • Patient may have adverse reactions (e.g., with food; failure to do so may reduce
ketoconazole, terbinafine, enilconazole, lime vomiting, diarrhea, hepatotoxicosis, vasculitis, bioavailability of these drugs by up to 40%.
sulfur, chlorhexidine) can be applied daily to lightening of haircoat, pruritus) to systemic • When not contraindicated, most allergic dogs
weekly, depending on the formulation used azoles. benefit from a short course of antipruritic/
(e.g., shampoo, solution, lotion, spray, wipe, • Ketoconazole may inhibit cortisol synthesis antiinflammatory therapy (e.g., glucocor-
mousse). at dosages greater than 10 mg/kg/day. ticoid, oclacitinib, lokivetmab) during the
• Systemic antifungal therapy may be warranted initiation of other antiyeast measures (p. 91).
for severe infections or those not respond- Recommended Monitoring
ing to topical therapy alone. Duration of • Clinical signs and cytologic evaluation every Prevention
systemic therapy should persist beyond (e.g., 3-4 weeks during therapy Correctly identifying and treating for all
1-2 weeks) clinical and cytologic resolution • Other monitoring recommendations are at underlying predisposing factors favorable to
(usually a minimum of 3-4 weeks). Griseoful- the discretion of the clinician and based on yeast overgrowth
vin has no effect against Malassezia species, underlying predisposing diseases.
and terbinafine may not be as effective as Technician Tips
azoles. PROGNOSIS & OUTCOME Technicians managing patients with Malassezia
○ Ketoconazole 5-10 mg/kg PO q 24h with dermatitis should be proficient in collection and
food; other azoles better suited for cats, • Failure to detect and treat underlying exam of cytologic skin samples (p. 1091) and
or disease(s) will result in partial treatment capable of instructing owners on appropriate
○ Itraconazole 5-10 mg/kg PO q 24h with success, treatment failure, or relapse. use of topical therapy.
(capsules) or without (suspension) food, • For incurable diseases (e.g., primary corni-
or fication disorders), therapy for Malassezia Client Education
○ Fluconazole 2.5-5 mg/kg PO q 24h, or dermatitis is often lifelong. • The identification of Malassezia dermatitis is
○ Terbinafine 30 mg/kg PO q 24h with only the beginning of the diagnostic process
food PEARLS & CONSIDERATIONS because yeast overgrowth is secondary to
• Because ≈40% of dogs with Malassezia another condition.
dermatitis have concurrent superficial staphy- Comments • Show clients how to effectively use topical
lococcal pyoderma, treating any associated • Malassezia dermatitis is one of the most antiyeast treatments.
bacterial infection with oral antibiotics at an overlooked causes of pruritus in the dog.
appropriate dose and duration (minimum 3 • Malassezia dermatitis tends to occur in body SUGGESTED READING
weeks) can help improve cutaneous signs. areas rich in sebaceous glands and high in Negre A, et al: Evidence-based veterinary dermatology:
relative humidity, and it is commonly associ- a systematic review of interventions for Malassezia
Chronic Treatment ated with allergic dermatitis. dermatitis in dogs. Vet Dermatol 20:1-12, 2008.
• Therapy for underlying predisposing diseases • How many yeasts are cytologically significant? AUTHOR: Adam P. Patterson, DVM, DACVD
• Topical keratomodulating and/or antiyeast Finding any yeast from typical clinical EDITOR: Manon Paradis, DMV, MVSc, DACVD
therapy at reduced frequencies of application lesions is significant. However, because false-
if possible negatives are possible with cytology, typical
• Pulse therapy with a systemic azole or signs and pruritic distribution pattern (body
terbinafine can be used for remitting and folds) should not be taken lightly when
relapsing episodes of Malassezia dermatitis making a diagnosis.
because these drugs concentrate in the skin. • Dogs with atopic dermatitis may be hyper-
Typically, the same initial dosage is prescribed sensitive to Malassezia, resulting in yeast

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