Exam 2 - Autoimmune Skin Diseases

Question 1

what is a self marker in regards to the immune system?

Answer 1

self marker (MHC) labels the body’s cells as a friend & are tolerated by the immune system

Question 2

what is an antigen?

Answer 2

molecule that the immune system recognizes as foreign (non-self) & treats as a foe

Question 3

what is the common history of a patient with an immune-mediated skin disease?

Answer 3

severe disease with acute/rapid onset with reports that lesions wax/wane in short cycles of 7-10 days

intermittent episodes of systemic illness concurrent with the development of lesions

lack of response to appropriate therapy for non-immune mediated disease

difficulty eating/drinking - may be early sign of oral ulceration

Question 4

what lesion distribution should make you think of immune-mediated skin disease?

Answer 4

involvement of the nasal planum, ear pinnae, or foot pads (non-haired skin)

Question 5

what part of lesion development may clue you in to an immune-mediated issue seen on physical exam?

Answer 5

large numbers of intact primary lesions that are easily found & are in the same stage (all pustules/vesicles/bullae without epidermal collarettes)

Question 6

what diagnostic test should be considered sooner in a patient’s work up for potential immune-mediated skin disease? why?

Answer 6

skin biopsy - best chance for definitive diagnosis

Question 7

what is the minimum database needed when working up a patient for a potential immune-mediated disease?

Answer 7

skin scrapings & cytology - rule out parasites & infections

Question 8

why not surgically scrub/prep the skin site for biopsy?

Answer 8

you can wash away the diagnostic sample

Question 9

why is the top option for biopsy unacceptable but everything beneath is?

Answer 9

including both normal & abnormal in one sample can be misinterpreted by the pathologist depending on how the sample is cut & processed

Question 10

what is considered to be the mainstay of therapy for immune-mediated skin conditions?

Answer 10

glucocorticoids - often used initially to get disease into a rapid remission & then tapered

Question 11

when is cyclosporine best for treating immune-mediated skin disease?

Answer 11

best for t-cell mediated diseases such as lupus & perianal fistulas

Question 12

what is the MOA of tacrolimus? when is it best used in immune-mediated skin disease?

Answer 12

calcineurin inhibitor like cyclosporine that is much more potent - best for localized disease such as discoid lupus erythematous & perianal fistulas

owners must wear gloves

Question 13

why not use azathioprine in cats?

Answer 13

can cause fatal leukopenia & thrombocytopenia

Question 14

when is azathioprine & chlorambucil best used for immune-mediated skin disease?

Answer 14

in combination with other immunosuppressives - most beneficial for glucocorticoid dose sparing effects

Question 15

when is mycophenolate mofetil best used for immune-mediated skin disease?

Answer 15

effective in most cases of pemphigus foliaceus

Question 16

when is leflunomide best used for immune-mediated skin disease?

Answer 16

histiocytic diseases - may be beneficial in other round cell diseases

Question 17

what is the MOA of pentoxifyline? when is it best used for immune-mediated skin disease?

Answer 17

phosphodiesterase inhibitor that allows for more deformability with red blood cels

good choice for vasculitis cases

Question 18

what is the main goal of therapy when treating immune-mediated skin disease?

Answer 18

get disease into a clinical remission with medications & then taper to the lowest dose possible to keep the disease managed

Question 19

this distribution is seen with what immune-mediated skin condition?

Answer 19

pemphigus foliaceus

Question 20

what is the pathogenesis of pemphigus foliaceus?

Answer 20

immune system makes an attack on the adhesion molecules that hold the skin together

in pemphigus foliaceus - attack is only on part of the desmosome & where the cells are most concentrated is where the lesion target is

as the adhesion molecules separate, a pustule forms

Question 21

what is seen on biopsy that is pretty definitive for pemphigus foliaceus?

Answer 21

acantholytic keratinocytes - immature skin cell that has lost its attachment to its neighbors, rounded edges

subcorneal pustules, neutrophils but no bacteria representing a sterile inflammatory process

Question 22

this distribution is seen with what immune-mediated skin condition?

Answer 22

cutaneous vasculitis

Question 23

how can you differentiate between erythema on skin & lesions that represent bleeding?

Answer 23

erythema will blanch when you press a slide down on it

bleeding doesn’t blanch

Question 24

what are you paying attention to with lesions, lesion locations & symmetry that may indicate an immune-mediated dermatological disease is present?

Answer 24

lesions will all be in the same state - all pustules, all crusts, won’t see different stages, & pustules are much larger in pemphigus

immune-mediated diseases can affect both haired & non-haired skin

especially if on the nasal planum & paw pads!!!!!!

symmetry is very common in immune-mediated dermatological diseases

Question 25

what is an example of when you may consider the presence of an immune-mediated dermatological disease in a patient you treated for folliculitis?

Answer 25

the patient presents with signs of folliculitis (lesions are affecting haired skin, pustules are seen) , so empirical therapy is administered but the patient has no response to it consider pemphigus - autoimmune disease that features pustules!!!

Question 26

why is biopsy pursued earlier in immune-mediated dermatological diseases?

Answer 26

gives you the most bang for your buck - especially if lesions are present on nasal planum/paw pads gets you a definitive diagnosis quicker

Question 27

T/F: cats with pemphigus respond well to cyclosporine as treatment while dogs do not

Answer 27

true

Question 28

why should you not give a cat azathioprine for an immune-mediated dermatological disease?

Answer 28

causes myelosuppression (and maybe liver toxicity?)

Question 29

T/F: many general practitioners fail at treating immune-mediated skin diseases because they taper immunosuppressive drugs too quickly

Answer 29

true

Question 30

what is the schedule used for tapering immunosuppressive drugs for autoimmune skin diseases?

Answer 30

tapering is extremely slow - decrease of about 20% every 10-14 days

Question 31

what is the most common dermatological autoimmune disease seen in companion animals?

Answer 31

pemphigus foliaceus

Question 32

how can pustules on the skin of a dog help clue you in to an immune-mediated disease?

Answer 32

pustules in pemphigus are huge & span multiple hair follicles in folliculitis - pustules are smaller because individual follicles are affected

Question 33

what is shown here that concerns you for an immune-mediated disease?

Answer 33

pustule is present on the actual paw pad

Question 34

what cell types are shown on this biopsy sample of the nasal planum of a dog? what do you think the dog has?

Answer 34

acantholytic keratinocytes pemphigus foliaceus

Question 35

T/F: the concave surface of the pinna is a common site for lesions in immune-mediated dermatological disease

Answer 35

true

Question 36

the lesion distribution shown is for what disease in cats?

Answer 36

pemphigus foliaceus in cats

Question 37

will you scrub a crust before taking a biopsy sample when looking for immune-mediated skin disease? why? what should you do?

Answer 37

NO - you will literally wash away your evidence you dummy biopsy through the crust!!!

Question 38

will you see pustules on cats with pemphigus? why?

Answer 38

not really - they suck at making them you'll probably see crusts instead

Question 39

what disease has the lesion distribution shown in the photo? why?

Answer 39

cutaneous vasculitis - lesions are on the distal extremities because of smaller vessels & how they are affected

Question 40

because cutaneous vasculitis has a lot of triggers associated with its cause, where can you start after taking a biopsy?

Answer 40

run a 4DX

Question 41

what is the pathogenesis of cutaneous vasculitis?

Answer 41

type III hypersensitivity reaction - antigen-antibody complexes are deposited inside vessel walls & the body can't effectively clear them complexes result in lymphocyte recruitment & complement fixation. Damage is believed to be mediated by the cleaved complement anaphylotoxins, C3a (initiates mast cell degranulation) & C5a (encourages inflammatory cell recruitment in tissues resulting in massive damage to the blood vessel wall) fibrin deposition enables thrombus formation - tissue necrosis & movement of red blood cells outside the vessel wall (extravasation) are the ultimate outcome

Question 42

what is seen on biopsy that is supportive of cutaneous vasculitis?

Answer 42

bubbling on the basement membrane, separation at the basement membrane when active - lesions will show up as erosions/ulcers (especially at the ear margin because of those teeny tiny vessels)

Question 43

what immune-mediated disease do you think is going on?

Answer 43

cutaneous vasculitis - little hole punch looking things

Question 44

what is the only way to definitively diagnose cutaneous vasculitis?

Answer 44

histopathology - lesions without marked ulceration and necrosis are preferred extravasation of red blood cells is common fibrinoid necrosis is the end point of immune-mediated blood vessel wall destruction in some cases, only changes associated with vasculitis (i.e. necrosis, fibrinoid change, endothelial swelling, thrombosis) are seen