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feline skin diseasees:

kevin p byrne

cats in some 
respects are easier to deal with than dogs, as long as they're 
well-mannered. 

mostly they are rewarding as far as tx of skin dz, in 
general most people have good experiences dealing with cats, unless they 
do not like them. mostly nice patients. 

there is a handout; some 
handouts are double sided and some are single sided

the coat color thing 
is just FYI.

Feline acne:

relatively common problem seen in feline 
patients. owners may be unaware of it. observant owners will notice it. 
they see comedones, blackheads, or "dirty chin."

any age, sex, breed. 
keratinization disorder. may be totally non-pruritic, no actual problems. 
pathogenesis is multifactorial...sometimes yeast, staph associated with 
this problem, sometimes not, unsure of relation to pathogenesis. may be 
opportunistic. role of cleaning? decreased grooming might have an affect. 


typical dermatologic findings:
open comedones (follicular plugs - open = 
blackhead, closed = whitehead) on chin
papules and pustules may be 
present
suppurative folliculitis may occur
ddx: demodex, dermatophytosis, 
EGC (eosinophilic granuloma complex)

slide: cat with "dirty chin"
slide: 
cat with drainage, folliculitis, furunculosis - probably needs 
antibiotics. most cases just require some cleaning/washing the chin; once 
it looks like this usually there's secondary bacterial involvement 
though.
slide; some kitties get a rather dramatic amount of exudate on 
the ventral chin, here it has spread all over the whole ventral chin and 
even part of the upper lip area which makes you wonder if something else 
is going on. it's all crusted and draining. bleah.

dx: PE, cytology. for 
mild cases dx is really limited to PE findings and then we recommend a 
benzoyl peroxide or chlorhexidine shampoo to wash the area. 
severe cases 
- systemic abx may be needed.

topical therapy:
mild cases: benzoyl 
peroxide or chlorhexidine wash once a day or every other day
topical 
metronidazole (metro-gel; used for people with rosacea); tretinoin 
(retin-a cream; or retin-a gel is also available but is more drying and 
irritating whereas the cream is more soothing and is in a higher 
concentration of drug); antibiotics - topical formulations of 
erythromycin or clindamycin. 

Malassezia dermatitis: not too terribly 
common, but occuring more and more these days; also seeing it a lot in 
dogs of course. specifically - facial yeast dermatitis - bridge of nose, 
periocular, alopecia and hypotrichosis, some scaling, crusting. 
any age, 
any sex; persians predisposed
use of oil-based cyclosporine ophthalmics 
seems to be implicated in this facial yeast syndrome. 
local 
immunosuppression? or is the yeast feeding on the olive oil base of the 
cyclosporine preparation as it drips out of eyes??
skin findings: 
alopecia, erythema, scaling, periocular-facial.
ddx: demodecosis, 
dermatophytosis, allergy
tx: try to get off the oil-based cyclosporine 
and onto the human ophthalmic preparation, systemic or topical 
antifungals
dx: impression smear, cytology (may have to heat fix if oil 
is present), dermatopathology is used to rule out other possible 
infections. yeast isn't usually found on biopsy though b/c it gets washed 
off, is very superficial. 

Feline Tail Gland hyperplasia:

any age, 
breed, sex - but more common in males (high androgen levels may 
contribute)
confined cats who can't reach back to groom well
supracaudal 
organ
dermatologic findings: waxy seborrhea on dorsum of tail, bacterial 
folliculitis can set in too.

early tx: topical therapy, change housing

ddx: dermatophytosis, allergy if pruritic
tx: clip, wash area. topical 
therapy benzoyl peroxide, sulfur salicylic acid shampoo; antibiotics if 
severe secondary infections; remove from confinement.

Feline Miliary 
Dermatitis:
common. no age/breed/sex predilection
underlying causes: flea 
allergy, atopy, food allergy, cheyletiellosis, dermatophytosis.

FMD is a 
common manifestation of allergy in cats. most common underlying cause of 
this skin reaction pattern is a flea hypersensitivity - some people call 
this "Flea Miliary Dermatitis" (also FMD) but since these other causes 
can cause the same pattern...that's not that useful.
skin findings: 
dorsum, neck, medial thigh, flanks covered with little 1-2 mm 
papulocrustous lesions, with erythema, alopecia and excoriations. 
sometimes a couple of the little lesions coalesce into a bigger lesion. 
these are packed with eosinophils and there may or may not be a lot of 
alopecia. if alopecia is present it is due to self trauma. if there is no 
self trauma, cat may present for "bumps" felt when owner pets the cat. 
then if you part the hair you can see them. when there is marked allergic 
response you may also feel enlarged LNs, even generalized lymphadenopathy 
(reactive LN with increased eosinophils on cytology); sometimes 
eosinophilia on CBC.
dx: PE findings, lack of signs of other disease, 
presence of fleas/flea dirt/dipylidium segments; flea-control trial is 
often diagnostic and therapeutic at the same time; r/o atopy, food 
allergy, other parasites, dermatophyte; dermatopathology is not helpful 
b/c it will just show this allergic pattern.
management: strict flea 
control which can be really hard if cats go outside. free roaming cats 
are very hard to control fleas on. for other non-flea cases, or things 
not managed well, glucocorticoids will clear up skin, decrease pruritis. 
also antihistamines - chlorpheniramine, atarax. it's sort of bad to use 
steroids at the same time you start flea control because you want to know 
if the pruritus decreases in response to the flea control. the 
antihistamines can help with the pruritus, not as much as steroids, but 
can be helpful.

EGC - eosinophilic granuloma complex:  

three diseases 
involved in this complex; cats may have 1 or 2 or all 3. more common to 
have plaque and granuloma than all three together but can happen.

feline 
indolent ulcer:

common - any age, breed; females more affected

for 
indolent ulcer form:
skin findings:
ulcerated lesions, upper lip - 
midline
circumscribed, red-yellow
nonpruritic
usually painless
slide: 
prototypical lesion - bilaterally symmetrical (not always), with dished 
out, ulcerated appearance, salmon colored, moist, glistening surface. not 
pruritic or painful early on. can become painful later on or be painful 
on manipulation. 
sometimes asymmetrical - this one is on only the right 
side of the upper lip. this cat was on depo-medrol shots for many years, 
and did respond to it but then stopped responding - about 1 week after 
the shot the lesion would come back. this cat was food allergic and the 
only thing that would make this lesion go away was some special diet and 
this cleared up right away. 
slide: really awful, nasty, necrotic looking 
lesions of upper lip. 

ddx: neoplasia - SCC, MCT, LSA; infectious - 
fungal, viral, bacterial; trauma
the first time you see the lesion, 
assuming it isn't proliferative, you won't think it's likely to be 
neoplastic, and you go ahead and treat the way you think it should be 
treated, but you tell the owner that you might need to biopsy if it 
doesn't respond. if a cat comes in after long-term failure to respond to 
therapy, you should biopsy it.
"rodent ulcer" was the term used b/c 
people thought cat was bitten by a rat or something weird like that.


other clinical findings with these things:
lymphadenopathy of 
submandibular and/or prescapular LNs; peripheral eosinophilia is uncommon 
with the indolent ulcer syndrome
may be FeLV positive -there does seem to 
be some correlation with the indolent ulcers and FeLV
dx: cytology, 
impression smears probably pick up necrotic stuff and maybe some 
eosinophils; cellular atypia may spur you to biopsy lesion. 
dermatopathology is diagnostic. fungal/bacterial cultures can also be 
done. 
chronic cases: r/o atopy, food allergy, flea allergy; tx with 
antibiotics - some cats do really well in response to abx perhaps b/c 
they kill secondary bacterial infections, not really sure; 
glucocorticoids usually really help - can give orally, systemic 
injection, or local injection under sedation; other tx include interferon 
alpha and possibly CO2 laser ablation or photodynamic therapy

EGC: 
eosinophilic plaque form
common
any sex, breed; more often in younger 
cats
stronger association with allergy - controlling allergy usually 
controls the plaques.
lesions intensely pruritic - unlike the indolent 
ulcers. cat will be constantly licking, chewing, etc. 
skin findings: 
ventrum, flank, medial thigh; moist, erythematous lesions. 
papules/plaques - sharply demarcated. initially may look like small 
papules but rapidly coalesce into plaques looking red, angry, raised. 
when the surface is glistening usually a secondary bacterial infection is 
present and abx will be useful therapy. 

ddx: fungal, neoplasia, 
bacterial. big one is neoplasia b/c lesion is raised, proliferative. 
could be cutaneous LSA. we had a cat come in with this lesion that failed 
to respond to depo, and it had cutaneous LSA on biopsy. 
slide: ventral 
aspect of this cat showing red, raised, plaquelike lesions. some self 
trauma, excoriations seen caudally. area is alopecic from licking.


slide: typical patient - large ventral lesions and some self trauma 
excoriations on the side of the neck. the abdominal lesion is a well 
demarcated area of coalescing papules/plaques, red and moist. 

other 
findings: lymphadenopathy is very common, usually reactive LN with 
eosinophils. peripheral eosinophilia is common in this syndrome. dx: 
cytology, dermatopathology. cytology will show eosinophils and that's 
considered diagnostic at first. if there are any questions, can biopsy. 


management: tx underlying cause - allergy. abx for secondary infections; 
glucocorticoids which in general are methylprednisolone in cats; other 
therapies probably not needed but for refractory case or whatever, 
interferon alpha may be used. 

EGC: eosinophilic granuloma
any breed; 
young female cats.
linear - 2-4 mm wide yellow lesion or 
papular to 
nodular, yello-pink; or
feline chin edema
other sites
ddx: neoplasia, 
bacterial, fungal
most often linear lesion on caudal thigh - raised, 
thickened, linear plaque type lesion. pretty compatible with this complex 
esp in young cat with other signs...might tx medically w/o biopsy but if 
any questions should biopsy.
slide: siamese type kitten with similar 
lesion on medial part of rear leg. some self trauma to area which is 
typical. 
here's where it gets interesting - this granuloma is present on 
the caudal aspect of the tongue, and the lesion has expanded and 
infiltrated the whole area with lots of caseous necrosis on top. looks 
like SCC or fibrosarcoma or something. would have to biopsy this. 
you 
can also have perirectal formation - here, there is no erosive component 
- it's infiltrative, around the rectal area; consider infectious or 
neoplastic process as well. those are sort of tricky.

the pouting cat - 
swollen chin - some kitties get eosinophilic infiltrate of chin and 
develop this pouting look; this is another manifestation of eosinophilic 
granuloma. but you need histopath to prove it.

other findings: 
eosinophilia (peripheral); 
dx: cytology, dermatopathology showing 
collagen degeneration/lysis unlike other two types of EGC lesions.

management: as for eosinophilic plaques

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someone asked about 
plastic food bowls. they used to be very irritating but the newer food 
bowls (we think) use different, less irritating plasticizers. however, if 
cat is using plastic bowl and has chin/facial dermatitis, we do ask them 
to switch bowls.

Psychogenic Alopecia and Dermatitis:

excessive 
grooming - anxiety
-barbering, hair pulling, excoriations
-history of 
stressful event
endorphins may reinforce behavior as with acral lick 
dermatitis or lick granulomas in dogs (?? dr. overall said something 
about this *not* being the case with respect to OCD...I wonder if this is 
in any way related?0
any age, sex - esp abbysinians, siamese.

skin 
findings:
convenient areas to lick
trichogram shows broken hairs
first 
clue is that if you run a hand over the hair, you feel areas where there 
is "stubble alopecia" as opposed to an actual bald area. also, you can 
pluck out some hair and examine the distal end to see if it's cleaved 
straight across from being broken/chewed or if it's normally tapered. 

ddx: allergy, dermatophytosis, demodecosis, cheyletiellosis, Otodectes

other findings:
CBC - no eosinophlia. if eosinophilia is present, think 
allergy.

owners will come up to you and say they think the cat has an 
endocrine problem - but no endocrine problem causes hair loss of caudal 
half of cat, and totally normal hair on cranial half of cat. 

dx: 
history, r/o other diseases; E-collar trial - see if the problem improves 
while cat wears an e-collar for a couple of weeks; trial of 
glucocorticoids; dermatopathology (normal skin = supportive of 
psychogenic alopecia)

management: reduce stress, diazepam, other drugs


slide: cat with patchy alopecia on the side of the body from shoulder to 
knee. "fur mowing".
slide: this other cat has mowed off the hair on the 
whole region from the chest to the tip of tail, dorsum to belly. whoah. 


Feline Plasma Cell Pododermatitis:
rare - any age/breed/sex
dermatologic 
findings:
multiple pads on multiple paws affected
soft swelling
usually 
painless
may ulcerate
cause? some kind of immune stimulation causing 
clonal expansion of plasmacytes...no real idea what. they get soft, 
puffy, mushy feeling enlargements of the toepads. usually not much 
discomfort is caused. 

ddx: infectious diseases (rarely localize only to 
a few toepads of various feet); sterile pyogranulomatous dz, eosinophilic 
granuloma, neoplasia
other clinical findings:
hypergammaglobulinemia, 
polyclonal gammopathy
dx: cytology (FNA), dermatopathology  - area is 
heavily infiltrated with plasma cells. if you do a punch biopsy, try to 
avoid punching the bottom of the pad and go for the side area, because 
the kitty has to walk on this foot.
management: none if asymptomatic - 
these often resolve on their own. if the cat is in pain or discomfort, 
try tx with systemic glucocorticoids. 

Feline plasma cell stomatitis:

uncommon - any age, sex, breed
seen with chronic gingivitis &/or 
glossitis

predisposing factors: chronic stomatitis (antigenic 
stimulation), autoimmune disease
may be concurrent with PC-pododermatitis 
- uncommon, however.

dermatologic findings: fleshy, proliferative 
lesions in oral cavity - gum margins, arches, pharyngeal walls, etc.
ddx: 
EGC, herpes, panleukopenia, periodontal dz, neoplasia, systemic illness, 
FeLV, FIV, toxicity, chemical irritation - it does encompass a variety of 
differentials.

other findings: salivation, drooling, anorexia (due to 
pain), weight loss
diagnosis: r/o FeLV/FIV, cytology, bacterial cultures, 
histopathology

management: treat underlying causes (dental prophylaxis, 
treat any oral bacterial infections, etc), systemic abx, systemic 
glucocorticoids if no big infectious component; chrysotherapy in really 
difficult or nonresponsive cases (gold salt therapy).
prognosis: fair to 
poor. if bad periodontal dz is present and amenable to tx, prognosis is 
ok; if you can't find an underlying cause, cat is FeLV positive, etc, 
prognosis is much worse.

Bacterial cellulitis/abscess:

any age, breed - 
intact males more often
infected wounds: skin heals over wound. often 
occurs after cat fight.
organisms: pasteurella, strep, bacteroides, 
fusiform bacilli

dermatologic findings:
cellulitis - firm, painful

abscesses - fluctuant
pyrexia, leukocytosis

management: surgical 
drainage, thorough flushing, systemic abx; if tx failure occurs check 
FeLV/FIV status, consider less common organisms like mycobacterial L 
forms or whatever. 

Cuterebriasis:
larva of cuterebra flies - 
swelling 
over head or neck area; possibly more often in kittens.
large swelling 
with a fistula and a larva inside
management: extract the larva without 
popping it b/c of possible allergic reaction; treat as infected wound.

rabbits also get this.

Opportunistic mycobacterial infections - fairly 
important group of infectious diseases which do affect dogs but which 
some of these organisms occur more commonly in cats and can be very 
problematic. you may initially examine the cat and think it is an abscess 
adn you tx appropriately and it doesn't get better or it gets better and 
then worse again..or cat comes in with history of wound being there x 1 
year and has had surgical drainage but still never healed...
this 
opportunistic mycobacterial infection is ddx in any nodular skin lesion 
in dog or cat...usually a group IV organism - these are ubiquitous - in 
dirt, goldfish bowls, etc. group III is the M.avium complex and can also 
be found sometimes in cats and dogs. as a whole, these infections are 
fairly uncommon in dogs/cats/humans

dermatologic findings:
draining 
fistulas, nodules, abscesses
ventral abdomen, inguinal area most often 
involved but not always; group III organisms usually more diffuse though.

ddx: nocardia, R. equi, L-form, other nodular infections

other clinical 
findings:
lethargy, decreased appetite, other signs of chronic illness 
like nonregenerative anemia. if group III infection, tends to disseminate 
- less likely to localize to skin. group IV prefer skin, do not usually 
disseminate to other organs.

dx: FeLV/FIV status - if positive, good 
luck, hard to control these infections in normal cats even; cytology - 
usually few if any acid-fast rods are seen; culture - very important for 
diagnosis, but sensitivity (mycobacterial sensitivity is very expensive 
btw but should still be done) may or may not be useful, realize need 
skilled lab b/c not all labs can grow these out; dermatopathology - 
excisional, not punch biopsy unless you use double punch technique - need 
deep tissue. one cat on one section, at the very bottom, had just  a few 
acid fast organisms. it's easy to miss.

management: 
excision if lesion 
is excisable; also need long-term antibiotic therapy. b/c some of these 
infections tend to wax and wane, can't rely on clinical resolution to 
decide when to stop abx. tell owner this is almost like dealing with 
cancer with respect to controlling it - need to treat for several months 
after apparent clinical cure and monitor for months as well b/c recurs 
very easily. 
enrofloxacin, clarithromycin are two drugs to try while 
awaiting sensitivity results. 
prognosis is guarded

slide: nasty area of 
ulcerations and fistulas, moist, exudative, edematous, inflamed area that 
has been present for months, periodically starting to resolve and then 
getting better. this is the type of lesion we see. 

sometimes presents 
as focal non-healing little wound, almost granulating appearance to it. 


Feline Leprosy: the other big mycobacterial disease in cats - etiology is 
M. lepraemurium (the rat leprosy organism).
skin findings: not like what 
you see with opportunistic mycobacteria. multiple firm, subcutaneous 
nodules, on the head, neck, trunk or rarely in oral cavity. 
other 
findings include lymphadenopathy (fairly common) or disseminated disease 
(rare).
ddx: opportunistic mycobacteria, fungal myecetoma, foriegn body, 
neoplasia, pseudomycetoma, nodular panniculitis

dx: many acid-fast rods 
on cytology or histopathology; absence of growth on mycobacterial culture

management: surgical excision; clofazimine, dapsone (cats susceptible to 
toxicity from this), streptomycin
slide: small nodular areas that are 
somewhat alopecic - clipping the areas reveals some drainage in this 
area, but generally multiple nodules should raise suspicion for leprosy, 
nocardia, possible opportunistic mycobacteria, etc.

Plague:
endemic 
areas = west of Rocky Mountains
yersinia pestis: zoonotic risk - direct 
contact w/infected wounds/lesions, bites by infected fleas
transmission 
to cat by infected rodent flea, inhalation, or ingestion
fulminating 
infection requires rapid therapy
dermatologic findings: abscess on head, 
neck; dx culture, immunofluorescence of smears, serology
management: 
streptomycin, gentamycin, tetracycline, combinations

Relapsing 
Polychondritis:
rare inflammation of cartilage
dermatologic findings:

swollen pinnae, curling of cartilage, waxes and wanes
slide: cat with 
curled up ear
this is an idiopathic  inflammatory condition of cartilage 
seen in cats and people.what happens is they go through these periods of 
time during which cartilage gets deformed due to inflammation of the 
pinna. other areas of body are affected but pinna most obvious to see. 
you get curling of the cartilage. there is no crusting, no surface 
disease. sometimes there is a little erythema. no tumor, no dermatitis 
per se. it's a cartilage problem. not skin. sometimes these cats are a 
bit pyrexic and may have other systemic signs. in humans, it's associated 
with lupus and other CT disease. 
dx: dermatopathology
management: none 
if asymptomatic; systemic glucocorticoids good to cut down on chronic 
changes 
other findings: pyrexia, neutrophilia

Feline solar dermatitis:

UV phototoxic reaction
dose related response
seen on nasal planum and 
sometimes pinna
may progress to SCC - first sun degeneration, then 
actinic keratosis, then SCC
usually white cat, sometimes orange: 
generally light colored hair coats, skin
sunbathers more at risk (dogs 
that lie on their backs, esp)

skin findings: ear tips, nasal planum, 
eyelids, head - areas with a little less hair covering them. erythematous 
macular lesions which become erosive and crusting.
ddx: autoimmune skin 
dz, drug eruption, pruritic excoriation, lymphoma, cold agglutin dz, 
frostbite. 

dx: history, PE, dermatopathology - variable findings

management: early: sun avoidance, sunblocks, topical steroids
actinic 
keratosis: (crusting, cellular atypia of dermal cells) cryotherapy 
ablation, photochemotherapy
SCC: surgical excision, radiation

Feline 
symmetric alopecia (endocrine alopecia)
real disease? 
true endocrine 
cause is not proven.
this disease may possibly exist but probably now 
that we dx so much allergic skin disease, we have fewer "idiopathic" or 
endocrine alopecias.
ddx: as for psychogenic alopecia; cushing's, 
hypothyroid, anagen or telogen defluxation.

dx: r/o ddx; trichogram or 
biopsy - mainly telogen hairs (normal cats you find a mix of anagen and 
telogen hairs)
management: tx underlying cause; if can't find underlying 
cause can try testosterone 12.5 mg IM but causes urine spraying, 
aggressiveness.

Feline skin fragility syndrome:
FSFS
acquired disease

any age, sex, breed
history of progestagen use
secondary to HAC - rarely 
seen with parenteral glucocorticoids
cause: use of ovaban or other 
progestagens, or cushing's type state
skin findings: skin tents very 
easily, minor trauma causes large gaping wounds which are hard to suture 
b/c of paper thin skin
(like rabbit skin)
avoid any trauma to skin - abx 
as needed for secondary infections.
discontinue any steroids
if 
iatrogenic, over time, can gradually improve when drug stopped (takes 
months)


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