Malassezia pachydermidis is commonly found on healthy skin and mucosa. It is an opportunistic pathogen of both cats and dogs, and during infection it may increase 100-10000 fold on the skin. It is most commonly recovered from the ear, anus, and the paws.
Some breeds are more predisposed than others, with Dachshunds and Cocker spaniels amongst the most commonly seen. M. pachydermidis is seen concurrently with a Staphylococcus intermedius infection.
Hot, humid conditions favour the development of the infection.
M. Pachydermatitis is bottle-shaped, and non-mycelial.
Gram stain shows purple yeast cells with a very wide base, and has a greenish discolouration on blood agar.
Grossly, regional lesions may be seen around the muzzle, ears, interdigital, and perianal. Other common signs include erythema, hyperpigmentation, lichenified and scaly lesions with alopecia.
Microscopically, one may see;hyperkeratosis, parakeratosis, Spongiotic pustular dermatitis, Acanthosis. Organisms are usually present- minimum 3-5 yeasts per high-power field must be found to imply cause of disease