Dermatology Diagnostics, Topical therapy pt 2 Flashcards
cytology for malassezia - techniques
Impression
Swab
Tape prep
Acantholytic keratinocytes - what are they? appearance?
Acantholytic keratinocytes are rounded epithelial cells (purple cytoplasm with dark purple nucleus. Cytoplasm is not foamy
like macrophages and cell is usually larger than macrophages
Acantholytic keratinocytes are caused by what?
- breakdown of the “bridges” (desmosomes) between epithelial cells.
What can lead to the presence of acantholytic keratinocytes?
- Dermatophytosis (Trichophyton)
- Pemphigus foliaceus
- Bacterial skin disease
Otic Cytology
- colonization vs infection?
- numbers and significance? for dog and cat
- Bacteria or yeast that are noted within the cerumen or on epithelial cells with few inflammatory cells present may be indicative of colonization, not infection
<><> - Small numbers of bacteria and yeast are normal
> Dog: Malassezia >5/HPF or bacteria >25
> Cat: Malassezia > 12/HPF or bacteria >15
in the cat were considered abnormal
Mycological tests – Wood’s Lamp
- how to, for Microsporum canis?
- efficacy? what we see?
- Plug-in Wood’s lamp with a wavelength of 320 to 400 nm and built-in magnification
- In recent in vivo studies, 91% to 100% of M. canis patients with untreated spontaneous infections showed positive fluorescence.
- Apple-green fluorescence on the
hair shaft suggests of M canis
Fungal culture, PCR
- technique for collection?
- PCR consideration?
“Mackenzie brush” technique to identify spores on the haircoat:
- Better results vs plating hairs
- Positive fungal cultures from whole-body toothbrush samples may be due to true
disease or fomite carriage; thus, sampling should be limited to lesion sites
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- PCR detects both viable and non viable DNA
Bacterial culture for Superficial Pyoderma
- how to sample?
- Lift edge of collarette and carefully rub with a sterile swab
- “Pop a zit”
skin biopsy for itchy dog - should we do it?
Skin biopsy does not tell the practitioner why the pet is pruritic and should be reserved for cases where parasites, infection and hypersensitivity are ruled out (e.g. T-cell lymphoma, paraneoplastic alopecia)
Where is the best place to biopsy?
Depends on the condition!
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- Pustule
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- Ulcer: Elliptical (best) or at least non ulcerated skin from the closest margin
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- Alopecia: get the largest sample collected from the baldest area
> take normal sample and place in a different container
> be careful about taking samples from the margins (same as ulcer)
Skin Biopsy – the procedure
- Shorten the hairs with clippers or scissors; DO NOT Shave to the skin
- Mark the site with a marker
- Local anesthetic is placed below the site into the subcutaneous tissue (be careful not to get it into the dermis)
- If panniculitis is suspected, use a ring block
<><> - Bakers biopsy punch
- firmly place punch against skin
- nodules and bullae may be excised with an elliptical incision
<><> - Firm pressure is applied and the punch is rotated in one direction to avoid a shearing effect
- Rotation continues until the punch “pops” through to the subcutis
- The sample may need to be cut free
- Ensure that the tissue is only handled at the
subcutaneous layer
<><> - Tissue is placed in formalin and labeled.
- TIP: multiple containers can be used to differentiate sites or appearance (tongue depressor tip?)
- Wound is closed with either a cruciate pattern or simple interrupted suture or a staple
Skin biopsy – important tips
- who to send it to and why?
- what to include?
Be sure to use a veterinary dermatohistopathologist - these pathologists attend the dermatology meetings and have extra expertise (the diagnosis is only as good as sample collection and the pathologist who reads the sample)
Be sure to give the pathologist as much history as possible as well as a list of differential diagnoses
Whenever possible digital photographs should be submitted
Fine Needle Aspirate - how to?
22 ga needle is placed on a 5-12 ml syringe
Needle is placed into the lesion and gentle suction is applied on the syringe
“Pump” the syringe a few times
Suction is released and the needle is redirected
Procedure is repeated as needed
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Once the sample is collected, detach the needle from the syringe and fill the syringe with air
Re-attach the needle and gently express the tissue from the needle;
Squash smear the sample (taking two slides and sliding one on another)
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FNA Tips:
Don’t “fire it” onto the microscope slide; this will decrease the “splash” effect
This technique can also be used for indurated (firm) tissue (doesn’t have to be a lump)
If mast cell tumour is suspected, better stains available at the lab (metachromatic) that may pick up mast cells which could be missed with Diff- Quick or similar stains used in hospitals
Highly vascular nodules might be better evaluated with the needle placed directly into the lesion without suction.
The sample is redirected and rotated to collect a “core” sample
The air-filled syringe is attached to the needle and the sample is expressed on to the slide
The sample is smeared on the slide, air dried and sent to the pathologist (better stains available there) or stained as you would a blood smear and examined in hospital (or both).
Shampoo therapies – functions
- Physical removal of microbes
- Physical removal of allergens
- Increase in skin hydration and direct soothing effect to the skin
why is there more staphylococcal pyoderma in patients suffering from atopic dermatitis?
increased adherence by pathogenic staphylococci to keratinocytes
