The purpose of this study was to investigate microbiological and histopathological features of canine acral lick dermatitis (ALD). Microbial characteristics of ALD are poorly described in current literature. If infection is recognized, antimicrobial selection is usually empirical, based on appearance, cytology or surface culture, rather than deep tissue culture. It was hypothesized that cultures obtained from deep tissue would yield different results than predicted by surface culture and cytology, and that isolates from ALD have unpredictable susceptibility patterns showing resistance to antibiotics routinely administered for canine pyoderma. Biopsies were obtained from 31 lesions and submitted for aerobic, anaerobic and fungal culture, and histopathological evaluation. Surface aerobic culture and susceptibility and cytology were obtained for comparison in 22 dogs. Skin scrapings and dermatophyte culture were performed. Bacteria were isolated in 30 of 31 cases. Staphylococcus intermedius was isolated in 58% of deep cultures. Twenty per cent of deep isolates were methicillin-resistant Staphylococcus species. Forty-eight per cent of cases yielded organisms defined as multidrug resistant on deep culture. Only 57% and 55% of bacteria isolated from tissue culture were sensitive to amoxicillin-clavulanic acid and cefazolin, respectively. Cytology and superficial cultures did not correlate well with deep cultures. Surface culture predicted deep tissue isolates in eight of 22 cases. Microsporum gypseum was isolated from one dog. Histopathological features included acanthosis, follicular elongation, lymphoplasmacytic dermal inflammation, folliculitis, furunculosis, perihidradenitis, hidradenitis and vertical streaking fibrosis. Lesions associated with ALD warrant tissue bacterial cultures as the majority of cases yielded positive growth of bacteria differing from superficial culture and often resistant to empirical drugs.

Clinical, cytological, microbial and histopathological features of feline acne were investigated in 22 cats referred or volunteered to a veterinary dermatology practice in the south-west region of the USA. For comparison, same parameters were evaluated in five unaffected pet cats. Additionally, all cats were evaluated by immunohistochemistry (IHC) for the presence of feline calicivirus (FCV) and feline herpes virus (FHV-1) in acne lesions. The age of onset of acne in affected cats ranged from 6 months to 14 years with a median of 4 years. The most common dermatologic lesions were comedones (73%), alopecia (68%), crusts (55%), papules (45%) and erythema (41%). Pruritus was reported in 35% of the affected cats. Cytological evidence of Malassezia pachydermatitis was present on 4/22 (18%) of affected cats. Microsporum canis was isolated from a single affected cat. Bacteria were isolated from 10 of the 22 (45%) affected cats; coagulase-positive staphylococci and alpha-haemolytic streptococci were most common. Histopathological features included lymphoplasmacytic periductal inflammation (86%), sebaceous gland duct dilatation (73%), follicular keratosis with plugging and dilatation (59%), epitrichial gland occlusion and dilatation (32%), folliculitis (27%), pyogranulomatous sebaceous adenitis (23%) and furunculosis (23%). In one affected cat from a household with five cats, simultaneously having feline acne, FCV antigen was detected in the biopsy of the chin by IHC. Chin tissue samples from all other affected cats, as well as the five healthy cats, were negative by IHC for FCV and FHV-1 antigens.

Alopecia is a common presenting complaint in veterinary medicine and is known to occur secondary to numerous primary conditions. In this report, six unrelated dogs from three households were subsequently determined to have developed alopecia as a result of accidental transdermal exposure to their owners' topical hormone replacement therapy (THRT). All cases presented with alopecia ranging in duration from 2 mo to 2.5 yr. All dogs demonstrated alopecia affecting the ventral neck, thoracic and abdominal surfaces, proximal lateral extremities, and lateral trunk. At the time of initial presentation, five of six dogs were also noted to have physical exam findings suggestive of feminization. In all cases, serum total thyroxine was within normal reference range. Affected skin was biopsied in five dogs, and all samples demonstrated four similar histological characteristics: basal melanosis, epidermal and infundibular follicular hyperkeratosis, kenogen hair follicles, and small sebaceous glands. All dogs had elevated baseline estradiol levels, and four dogs had concurrent elevations of baseline progesterone. Average time to onset of clinical signs in those dogs was 5.5 mo after the owners started THRT. Following discontinuation of THRT by the owners, all dogs had complete resolution of their clinical signs by 5.5 mo.

Dorsal thermal necrosis should be considered as a differential diagnosis for dogs with dorsal cutaneous burns and a history of sun exposure in high external temperatures. Dogs with dark, short hair coats may be at an increased risk.

A six-year-old male castrated domestic long hair feline presented for evaluation of a progressive cutaneous nodular dermatosis and an acute onset of dyspnoea. The patient had an initial skin biopsy performed with a tentative diagnosis of mycobacteriosis; however, acid-fast stains were negative. Thoracic radiographs revealed multifocal, large pulmonary nodules. Aerobic bacterial, fungal and mycobacterial cultures, as well as Histoplasma and Cryptococcus antigen tests, were all negative. Re-evaluation of the biopsy provided a diagnosis of feline progressive dendritic cell histiocytosis. The samples revealed a focally marked to diffuse coalescing superficial to deep perivascular and periadnexal infiltrates of numerous moderately large histiocytic cells. Unfortunately, there is no successful treatment for this disease and the patient was humanely euthanased.