Cubbie is a 2 year old male neutered golden retriever with a 2-month history of lesions on the pinnae not resolving with empirical treatment. He has a history of seasonal pruritus during the spring and summer months, managed with once monthly Cytopoint injections
Andrew Simpson
Animal Dermatology Clinics
Wheaton, IL
September 2025
Subjective
Cubbie is a 2 year old male neutered golden retriever with a 2-month history of lesions on the pinnae not resolving with empirical treatment. He has a history of seasonal pruritus during the spring and summer months, managed with once monthly Cytopoint injections. Other than the lesions on the ear pinnae, the owner has not noticed any signs of otitis externa including head shaking, scratching/rubbing the ears, odor, or exudate from the ears. Cubbie receives sarolaner + moxidectin once monthly for flea, tick, heartworm, and intestinal parasite prevention. There were no other medications administered prior to the development of these lesions within the preceding 3 months, including any vaccinations.
Cubbie is fed an over-the-counter salmon and rice diet. There are no other animals in the household.
Upon initial presentation to his primary care veterinarian, he was found to have lesions isolated to the ear pinnae and no significant findings on otoscopic examination of the canals and tympanic membrane. He was treated topically with an ointment (neomycin-nystatin-thiostrepton-triamcinolone) twice daily applied to both pinnae for 14 days as well as cephalexin (23 mg/kg PO q12h) for 21 days, with no response. He was then referred to the dermatology referral clinic for further diagnostics and treatment.
Objective
Body Weight: 33.7 kg
Temperature: 99.3 F
Pulse: 90 bpm
Respiratory: 40 bpm
BAR
- General physical examination findings: no oral or ocular lesions present, lymph nodes palpated within normal limits, the abdomen was soft and non-painful on palpation, with an empty bladder. Thoracic auscultation revealed no murmurs or arrhythmias; lungs ausculted clearly in all fields.
- Dermatologic Examination: multiple erythematous papular to plaquiform lesions with mild hyperkeratosis measuring 4-8 mm present on the medial aspect of both pinnae. No other cutaneous lesions noted.
- Video-otoscopic Examination findings of both ears: minimal yellow cerumen adhered to the vertical aspect of the canal walls. No stenosis, erythema, hyperplasia, foreign bodies, ear mites, or masses noted. The tympanic membrane appeared intact and within normal limits.
Multiple erythematous papular to plaquiform lesions with mild hyperkeratosis measuring 4-8 mm present on the medial aspect of the left pinna.
Multiple erythematous papular to plaquiform lesions with mild hyperkeratosis measuring 4-8 mm present on the medial aspect of the right pinna.
Differential diagnoses for hyperkeratotic lesions on the pinnae: Papillomatosis, superficial bacterial pyoderma, psoriasiform lichenoid dermatosis, hyperkeratotic erythema multiforme, vitamin A-responsive dermatosis, zinc-responsive dermatosis, dermatophytosis, sterile pyogranulomatous dermatitis, cutaneous reactive histiocytosis, and cutaneous lymphoma.
Diagnostics
- Impression smear cytology of the pinnal lesions: neutrophils with 2+ diplococci
- Deep skin scraping of the pinnae: no mites noted
Based on the atypical presentation and lack of response to empirical oral and topical antibiotics, the owners elected to pursue skin biopsy under general anesthesia for histopathology and aerobic culture with susceptibility testing along with fungal culture.
- Aerobic culture and susceptibility testing of the pinnal skin: Staphylococcus pseudintermedius (resistance to cephalosporins, but susceptibility to clindamycin, doxycycline, minocycline, enrofloxacin, marbofloxacin, rifampin, and sulfa antibiotics).
- Fungal culture: no growth
- Histopathology: Moderate hyperkeratosis with acanthosis of the epidermis but no lymphocytic satellitosis or apoptosis within the epidermis. There was a severe band of lymphocytes and plasma cells within the superficial dermis.
Assessment
Based on the combined results of the histopathology and aerobic culture, the diagnosis is psoriasiform lichenoid dermatosis likely due to Staphylococcus pseudintermedius.
Treatment
Clindamycin 9 mg/kg PO q12h for 21 days
Outcome
Cubbie was rechecked 2 weeks after starting oral clindamycin. All lesions had resolved. Clindamycin was continued for 1 additional week beyond resolution. There was no recurrence of cutaneous lesions at the 6-month follow-up.
Discussion
Psoriasiform lichenoid dermatitis (PLD) is a rare cutaneous disease in dogs affecting various breeds, with suspected genetic predisposition in Springer Spaniels.1,2 The exact etiopathogenesis is not known, however, an aberrant immunologic response to Staphylococcus spp. is likely, given the complete response to oral antibiotic therapy and presence of cocci on histopathology.1,3 PLD can occur as an uncommon side effect to cyclosporine in dogs, but has been reported to occur independent of any other drugs.1-4
Lesions typically present as waxy to crusted, erythematous papules that can eventually coalesce to plaque lesions with yellow crusting. The medial aspect (concave) of the pinnae is most commonly targeted in addition to periocular regions, limbs, and the ventral abdomen.5
A definitive diagnosis is made based on skin biopsy. Skin cytology of lesions, as with any skin lesions, should help guide antimicrobial therapy. In the absence of clinical resolution as well as continued cytologic evidence of bacterial infection, aerobic culture and susceptibility should be performed to provide the best guidance for antimicrobial therapy. In mild, localized cases, topical antimicrobials such as chlorhexidine may be effective, although many cases likely require systemic antibiotics given the extent and severity of lesions.
In cases receiving cyclosporine, PLD should be placed higher on the list of differential diagnoses when hyperkeratotic or crusting papular to plaquiform lesions are observed on the pinna and ventral abdomen. After treating for bacterial pyoderma based on cytology +/- aerobic culture and susceptibility findings, cyclosporine should either be replaced with a different therapeutic agent to address the primary disease for which it was intended, or at least reduced in dose.
The prognosis for PLD is excellent in most cases of spontaneous disease. In cases due to cyclosporine, prognosis may depend on the ability to either lower the cyclosporine dose or find a suitable alternative to manage cutaneous disease.
References
Banovic F, Olivry T, Linder KE, Tobias JR. Pathology in practice. Psoriasiform lichenoid dermatitis. J Am Vet Med Assoc. 2014 Dec 1;245(11):1237-9.
Mason KV, Halliwell RE, McDougal BJ. Characterization of lichenoid-psoriasiform dermatosis of Springer Spaniels. J Am Vet Med Assoc 1986;189:897–901.
Werner AH. Psoriasiform-lichenoid-like dermatosis in three dogs treated with microemulsified cyclosporine A. J Am Vet Med Assoc 2003;223:1013–1016.
Gross TL, Halliwell RE, McDougal BJ, et al. Psoriasiform lichenoid dermatitis in the Springer Spaniel. Vet Pathol 1986;23:76–78.
Ihrke PJ, Walder EJ, Affolter VK. Hyperplastic diseases of the epidermis. In: Gross TL, ed. Skin diseases of the dog and cat. 2nd ed. Ames, Iowa: Blackwell Science Ltd, 2005;152–154.