A review of cutaneous hypersensitivity reactions in dogs: A diagnostician's guide to allergy.

Allergic dermatoses are common in people and domestic animals. Resultant lesions are routinely biopsied and submitted for histological examination to confirm a diagnosis or rule out diseases with overlapping or atypical clinical features. Diagnostic pathologists and clinicians are often faced with the difficult task of determining whether an allergic reaction pattern is present on both the microscopic and macroscopic levels and correlating histopathologic findings with clinical and historical data to achieve a precise clinical diagnosis. The bulk of the current veterinary literature on allergic dermatoses focuses on atopic dermatitis in dogs, distantly followed by cats, horses, and other animals. The objectives of this review are to demonstrate the key histopathologic and clinical diagnostic features of the various allergy-mediated reaction patterns, and to provide diagnosticians with a practical guide for clinicopathological correlations. Current concepts in the pathophysiology of immediate hypersensitivity reactions, with a focus on atopic dermatitis, are discussed. Points of potential histopathologic overlap between the "classic" allergic reaction pattern and less common inflammatory, predominately eosinophilic, conditions that may mimic this pattern will be discussed with the goal of highlighting the critical need for collaboration between pathologists and clinicians in furthering patient care.

Cutaneous mastocytosis in 8 young dogs and review of literature.

Cutaneous mastocytosis (CM) is a rare condition in young dogs characterized by multicentric cutaneous proliferation of neoplastic mast cells. Clinical data from 8 dogs that met inclusion criteria (age of onset less than 1.5 years, greater than 3 lesions) were obtained via a standardized survey. Biopsy samples were classified by the Kiupel/Patnaik grading systems and analyzed for c-KIT mutations. The median age of onset was 6 months (range: 2-17 months). Dogs had 5 to more than 50 lesions characterized as nodules, plaques, and papules. Seven dogs were pruritic. Clinical staging in 2 dogs did not reveal visceral involvement. No dogs had systemic illnesses at diagnosis. Histologically, CM was similar to cutaneous mast cell tumor (cMCT). Two dogs had neoplasms classified as high-grade/grade II while 6 dogs had low-grade/grade II neoplasms. No dogs had mutations in c-KIT exons 8 and 11. Treatment included antihistamines (8/8), corticosteroids (7/8), lokivetmab (3/8), and toceranib (1/8). Six dogs were alive with lesions at the end of the study with a median follow-up time of 898 days, while 2 dogs were euthanized. In dogs with high-grade/grade II neoplasms, one continued to develop lesions at 1922 days post-diagnosis, while the other dog was euthanized at 56 days post-diagnosis. One dog was euthanized 621 days post-diagnosis due to rupture of a neoplasm. CM occurs in young dogs and is histologically indistinguishable from cMCT. Current histologic grading systems did not apply uniformly to the dogs of the study and further studies are needed.

Postmortem urinary tract changes in cats with urethral obstruction.

OBJECTIVE: To report the gross and histopathological postmortem findings of the urinary tract and compare them to clinical severity of disease in cats with urethral obstruction (UO). DESIGN: Retrospective, observational, descriptive study. SETTING: University teaching hospital. ANIMALS: Fourteen cats from 2000 to 2014 with UO that had a complete postmortem examination. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Bladder lesions were moderate-severe in 10 of 14 (71%) and mild in 4 of 14 (29%) cats. Bladder lesions were diffuse in 8 of 14 (57%), multifocal in 3 of 14 (21%), and focal in 3 of 14 (21%) cats. Lymphocytic cystitis was noted in 11 of 14 cats (78%), and neutrophilic cystitis was noted in 10 of 14 (71%) bladders. Urethral lesions were moderate-severe in 4 of 14 (29%), mild in 4 of 14 (29%), and no urethral lesions were identified in 6 of 14 (43%) cats. Ureteral lesions were mild in 1 of 14 (7%), and no ureteral lesions were identified in 13 of 14 (93%) cats. There were moderate-severe histopathological renal lesions in 5 of 14 cats (36%), mild renal lesions in 6 of 14 (43%), and no renal lesions were identified in 3 of 14 cats (21%). Renal lesions were multifocal in 10 of 14 (71%) and regional in 1 of 14 cats (7%). In the kidneys, the most common inflammatory infiltrate was lymphoplasmacytic. The severity of urethral lesions was not associated with the severity of bladder lesions (P = 1.0). Hyperkalemia paralleled the severity of bladder (P = 0.02) and renal lesions (P = 0.04). An association between the severity of bladder lesions and degree of azotemia could not be determined due to small sample size and removal of the most azotemic cats. CONCLUSIONS: Substantial renal and urinary bladder inflammatory lesions were found in cats with UO. The severity of these findings paralleled the severity of blood potassium concentrations.