07/28/2026
NAVLE High-Yield Focus: Malassezia Otitis Externa 🐶🐱🩺
Let’s talk Ear Cytology & Otitis Externa for board prep! Yeast otitis is a staple NAVLE question, often presented as a clinical vignette or an image identification question.
1. Etiology & Primary vs. Secondary Causes
Primary Pathogen: Malassezia pachydermatitis (peanut-shaped/footprint/bowling-pin budding yeast).
Key Concept: Yeast is an opportunistic commmensal. Otitis is almost ALWAYS a secondary sign. NAVLE vignettes will often test if you know to look for the underlying cause:
Atopic Dermatitis (Most common primary trigger)
Cutaneous Adverse Food Reaction (CAFR)
Hypothyroidism / Cushing's (Hyperadrenocorticism)
Foreign bodies or stenotic ear canals
2. Clinical Presentation & Cytology
Classic Signs: Erythema, lichenification, hyperpigmentation, dark brown/black ceruminous exudate, pungent sweet or musty odor.
Cytology: In-house Diff-Quik or Gram stain showing >3–5 budding yeast organisms per high-power field (100\times oil immersion)—though exact thresholds vary, board questions look for obvious peanut-shaped clusters.
3. High-Yield NAVLE Board Questions & Pitfalls
⚠️ Rule Out Ototoxicity First:
ALWAYS check the integrity of the tympanic membrane before instilling ear cleansers or topical medications (especially aminoglycosides like gentamicin/neomycin or chlorhexidine conc. >0.2%), as they are ototoxic and cause deafness or vestibular dysfunction if the eardrum is ruptured.
⚠️ Feline Special Considerations:
Pure yeast otitis in cats is less common than dogs. If a cat presents with dark, waxy ear discharge and intense pruritus, rule out Otodectes cynotis (ear mites) or underlying systemic illness (e.g., FIV/FeLV) first!
📝 Sample NAVLE Practice Question
Q: A 4-year-old neutered male Golden Retriever presents with a 2-week history of bilateral head shaking, pinnal erythema, and dark brown waxy discharge. Cytology reveals heavy loads of footprint-shaped budding yeast. Which of the following is the most appropriate next diagnostic step to manage the underlying cause?
