DS: elab skin pathology Flashcards
How do horses often present if they have Dermatophilosis?
crusting skin disease
What is cefalexin?
first generation cephalosporin - good activity against gram positive and negative bacteria
What might purple streaks on an impression of pustular exudate be?
check to see if they lead from swollen/ hydropic nuclei and if they do they may be smeared out strands of chromatin
What is superficial pyoderma an infection of?
epidermis or follicular epithelium only, usually only triggers a neutrophilic response
What happens if pyoderma breaches the epithelial barrier?
a FB-like pyogranulomatous response ensues (especialy if infected hair follicles rupture as this sets free keratin into the dermis –> deep pyoderma) - therefore macrophages numerous, possibly some eosinophils
What is another name for a squame?
corneocyte
What does it mean that ‘the living epidermis is hyperplastic and spongiotic’?
spongiotic - there are clear spaces between keratinocytes representing oedema
What does absence of the inferior portions of the hair follicles suggest?
there is an ‘atrophic’ pattern wherein there is arrest of hair growth cycle at telogen phase (n.b. the inferior part is only present in anagen). In dogs this most often represent an endocrine disease.
From a hair pluck, what does the presence of a good number of anagen hairs in proportion to telogen hairs suggest?
that endocrinopathy is unlikely - endocrinopathies that affect canine skin tend to cause ‘telogenisation’ of the hair coat (i.e. by variable mechanisms they synchronise msot hairs into telogen phase)
What do follicular casts indicate? What do they often co-exist with?
a defect of follicular keratinisation. Commonly seen in idiopathic seborrhoea and sebaceous adenitis in dogs, and in some cases of demodicosis and dermatophytosis. Often co-exists with comedones.
What is a common cause of eosinophilic plaques in cats?
Flea allergy dermatitis
Does the presence of a Demodex canis ovum confirm demodicosis?
No - ideally you want to demonstrate multiple mites to confirm demodicosis. BUT finding immature LC stages is highly unusual in unaffected dogs so there is a strong suspicion that further sampling will demonstrate more mites.
How is dermatophyte ID classically achieved?
culture at 26 degrees, Sabouraud’s dextrose agar (SDA), colonies usually appear within 1-2 weeks, careful labs keep plates for 4 weeks before pronouncing a submission is negative.
- KEY IS THE GROSS COLONIAL AND MICROSCOPICAL MORPHOLOGY IN ID.
What does the macroconidium of a fungus suggest on culture?
incidental finding, no clinical relevance, merely indicates exposure to saprophytic fungi, only produced by dermatophyte fungi in culture and not on skin
Define saprobic
being in an environment rich in nutrients but relatively free of O2
