Histopathological study of feline eosinophilic dermatoses

A retrospective study was conducted on skin specimens from 24 cats with eosinophilic granuloma complex. The specimens were stained with haematoxylin and eosin and Gallego's trichrome stain. In all specimens, flame figures and/or large foci of so-called "collagen degeneration" were detected and histopathological features were not predictive of the clinical picture. Use of the term eosinophilic dermatosis was advocated in diagnostic dermatopathology. On trichrome-stained sections, normally stained collagen fibres were identified in the middle of both flame figures and large foci of "collagen degeneration" and the debris surrounding collagen bundles showed the same tinctorial properties as eosinophil granules. Eosinophil degranulation around collagen bundles seemed to represent the major pathogenetic event in these lesions, analogous with human flame figures. The term flame figures might therefore be more accurately used to designate those foci of eosinophilic to partly basophilic debris commonly referred to as "collagen degeneration".     

Piecemeal degranulation (PMD) morphology in feline circulating eosinophils

Buffy coat preparation from six cats with 600-4560 circulating eosinophils/microL was collected by either blood centrifugation or sedimentation, fixed in 2.5% glutaraldehyde, post-fixed in either 1% osmium or in 1.5% potassium ferrocyanide-reduced osmium, ultra-sectioned and examined by transmission electron microscopy. Ultrastructural changes of piecemeal degranulation (PMD), which is a mechanism of eosinophil granule contents release indicative of eosinophil activation, were observed in specific granules from all the samples examined. The spectrum of PMD included coarsening of the granule matrix, budding vesicles, fragmented granule cores and lucent granules. The number of presumably activated eosinophils with ultrastructural evidence of PMD did not correlate with the level of eosinophilia. The lack of correlation suggested that, analogously with humans, blood eosinophil count might not represent the best criterion to evaluate the contribution of eosinophils to tissue damage in certain feline eosinophil-associated diseases.     

Expression of RANTES mRNA in skin lesions of feline eosinophilic plaque

Abstract One of the mechanisms of eosinophil infiltration is its induction by chemoattractants such as regulated upon activation, normal T-expressed and secreted (RANTES) which is a cysteine–cysteine chemokine that mediates chemotaxis and activation of eosinophils in humans and mice. Skin lesions of feline eosinophilic plaque are characterized by a predominant infiltration of eosinophils. The mechanism(s) of eosinophilic infiltration in the skin and/or mucosa of cats is unknown. It is possible that RANTES is involved. To investigate the presence of RANTES in the skin of cats with eosinophilic plaques and nonaffected skin, we cloned and sequenced the full-length feline RANTES cDNA gene, in order to determine whether it is present in the skin of cats with eosinophilic plaques and/or if it is present in normal adjacent skin. We were able to document the the expression of RANTES mRNAs in skin with feline eosinophilic plaque as well as in normal cat skin. The full-length cDNA sequence of the RANTES gene (742 bp) contained a single open reading frame of 276 bp encoding a protein of 92 amino acids. The amino acid sequence of feline RANTES shared 67 and 74% sequence identity with that of bovine and mouse RANTES genes, respectively. RT–PCR analysis on RANTES mRNA in the skin of cats with eosinophilic plaque revealed that its expression was higher in the eosinophilic plaque skin lesions than in the normal skin. The result suggested that RANTES might play a role to induce eosinophil infiltration in feline eosinophilic plaque lesions.     

Cytologic, microbiologic, and biochemical analysis of bronchoalveolar lavage fluid obtained from 24 healthy cats

Twenty-four healthy cats underwent bronchoscopy and bronchoalveolar lavage to determine the normal cytologic environment of the lower respiratory tract of cats. Initial screening to ensure the health of the study population included complete histories, physical examinations, thoracic radiography, CBC, serologic tests for feline leukemia virus, feline immunodeficiency virus, and occult heartworm, and sugar and Baermann fecal flotation. In 18 cats, protected catheter brush samples of airway secretions from the lavaged lung segment were taken for culture of aerobic and anaerobic bacteria and mycoplasma. Bronchial lavage fluid (5 sequential 10-ml aliquots of normal saline solution) was pooled and filtered with cotton gauze. The unspun sample was used for determination of a total nucleated cell count. Lavage fluid was cytocentrifuged and 500 cells/slide were scored for determination of the cellular differential. Activity of lactate dehydrogenase and concentrations of total protein and IgG within the supernatant were measured, and assays were performed to detect the presence of IgA and IgM. Complete histologic evaluation of the lavaged lung of each of 6 random-source cats was performed after differential cell counting revealed 18% eosinophils within bronchoalveolar lavage fluid recovered from this group. Alveolar macrophages were the predominant cells encountered; however, a quarter of all cells recovered were eosinophils. A significant relationship was not found between the abundance of eosinophils in the lavage fluid, and either isolation of aerobic bacteria, high total nucleated cell counts, total protein concentrations, or activity of lactate dehydrogenase. Histologic evaluation of the lungs of 5 of 6 random-source cats revealed normal lungs in 2 cats, and minimal abnormal change in 3 others. Evaluation of the lungs from 1 random source cat revealed acute, mild eosinophilic bronchiolitis. We conclude that large numbers of eosinophils may be retrieved from the bronchoalveolar lavage fluid of healthy cats.     

Characterization of biological activities of feline eosinophil granule proteins

OBJECTIVE:To characterize eosinophil granule-derived proteins in cats. SAMPLE POPULATION: Eosinophils collected via peritoneal lavage from 2 cats. PROCEDURE: The cats were infested orally with Toxocara canis eggs and subsequently challenge-exposed with T. canis antigen injected IP to induce peritoneal eosinophilia; eosinophils were collected via peritoneal lavage. Eosinophil granule proteins were acid-extracted, separated by gel-filtration chromatography, and examined for their peroxidase, ribonuclease, and bactericidal activities; the N-terminal sequence of some of these proteins was determined and compared with homologue proteins from other species. RESULTS: 3 protein peaks were separated in the chromatogram. The first peak had both peroxidase and bactericidal activities. The second peak had ribonuclease and bactericidal activities, and the N-terminal sequence of the major protein was homologous with that of proteins of the ribonuclease A superfamily, including eosinophil ribonucleases from humans and other animal species. The third protein peak had bactericidal activity, and the N-terminal sequence of the major protein was homologous with that of human and murine major basic proteins. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that feline eosinophil granules contain major basic protein and eosinophil-associated ribonuclease and the granule proteins have peroxidase, ribonuclease, and bactericidal activities. In cats, characterization of eosinophil granule proteins may be useful in elucidation of the mechanism of tissue damage in eosinophil-associated diseases and development of new treatment options for those diseases. In addition, the identification of conserved structure and function of eosinophil granule proteins in cats is relevant from an evolutionary viewpoint.     

Collagen dysplasia (cutaneous asthenia) in a cat

Hereditary collagen dysplasias comprise a complex group of connective-tissue disorders that result in the reduced tensile strength of affected tissues. These processes are called cutaneous asthenia in the skin of dogs and cats. We report here the case of a crossbred male cat, aged 6 months, that presented with two skin wounds in the region of the right thorax and right iliac tuberosity. The skin of these regions and of the animal's dorsum was hyperextensible, smooth to the touch, and easily torn with minor trauma. Microscopic examination of skin samples revealed reduced dermal connective tissue consisting of shortened and fragmented collagen fibers. Normal fibers were intermingled with altered fibers. Ultrastructural changes in collagen fibers included disorientation of fibrils within the same bundle, marked spacing differences, and variation in the diameter of transverse sections. The fibrils maintained the transverse striations characteristic of normal collagen.     

A Case of Feline Gastrointestinal Eosinophilic Sclerosing Fibroplasia

Feline gastrointestinal eosinophilic sclerosing fibroplasia was diagnosed in an 8-month-old Scottish fold that had a primary gastrointestinal mass involving the stomach, duodenum and mesenteric lymph nodes. Histopathologically, the most characteristic feature of this mass was granulation tissue with eosinophil infiltration and hyperplasia of sclerosing collagen fiber. Immunohistochemically, large spindle-shaped cells were positive for smooth muscle actin and vimentin. This case emphasizes the importance of feline gastrointestinal eosinophilic sclerosing fibroplasia as a differential diagnosis of gastrointestinal neoplastic lesions such as osteosarcoma and mast cell tumor in cats.     

Abscess-forming inflammatory granulation tissue with Gram-positive cocci and prominent eosinophil infiltration in cats: possible infection of methicillin-resistant Staphylococcus

We occasionally encounter feline cervical or mesenteric lesions diagnosed histopathologically as abscess or inflammatory granulation tissue with eosinophil infiltration. Gram-positive cocci accompany the lesions. In the present study, such lesions obtained from 27 cats were examined to evaluate the histopathologic features and the nature of the causative bacteria. The average age was 7.3 +/- 3.5 years. No sex predilection was observed. Most frequent locations of the lesions included the abdominal cavity with/without mesenteric lymph nodes (11/27, 41%) and subcutaneous tissue or lymph nodes of the neck (9/27, 33%). Common clinical presentation was a localized mass. Grossly, the lesions contained abscesses in the center and were surrounded by fibrous tissue. Microscopically, the necrotic zone contained bacterial colonies. Large numbers of eosinophils and macrophages infiltrated the area surrounding the necrotic tissue. The surrounding connective fiber-rich granulation tissue demarcated the eosinophilic abscess. The bacteria were Gram-positive cocci in 23 of the 27 cats and were positive for anti-staphylococcus antiserum in 19 of the 23 cats. In 15 out of 17 lesions, the colonies expressed immunoreactivity to penicillin-binding protein 2', which is a drug-resistance gene product of methicillin-resistant Staphylococcus (MRS) species. These findings suggest strongly that MRS causes this type of infectious lesion.     

Comparison of white blood cell differential percentages determined by the in-house LaserCyte hematology analyzer and a manual method

BACKGROUND: The LaserCyte hematology analyzer (IDEXX Laboratories, Chalfont St. Peter, Bucks, UK) is the first in-house laser-based single channel flow cytometer designed specifically for veterinary practice. The instrument provides a full hematologic analysis including a 5-part WBC differential (LC-diff%). We are unaware of published studies comparing LC-diff% results to those determined by other methods used in practice. OBJECTIVE: To compare LC-diff% results to those obtained by a manual differential cell count (M-diff%). METHODS: Eighty-six venous blood samples from 44 dogs and 42 cats were collected into EDTA tubes at the Forest Veterinary Centre (Epping, UK). Samples were analyzed using the LaserCyte within 1 hour of collection. Unstained blood smears were then posted to Langford Veterinary Diagnostics, University of Bristol, and stained with modified Wright's stain. One hundred-cell manual differential counts were performed by 2 technicians and the mean percentage was calculated for each cell type. Data (LC-diff% vs M-diff%) were analyzed using Wilcoxon signed rank tests, Deming regression, and Bland-Altman difference plots. RESULTS: Significant differences between methods were found for neutrophil and monocyte percentages in samples from dogs and cats and for eosinophil percentage in samples from cats. Correlations (r) (canine/feline) were .55/.72 for neutrophils, .76/.69 for lymphocytes, .05/.29 for monocytes and .60/.82 for eosinophils. Agreement between LC-diff% and Mdiff% results was poor in samples from both species. Bland-Altman plots revealed outliers in samples with atypical WBCs (1 cat), leukocytosis (2 dogs, 9 cats), and leukopenia (16 dogs, 11 cats). The LaserCyte generated error flags in 28 of 86 (32.6%) samples, included 7 with leukopenia, 8 with lymphopenia, 7 with leukocytosis, 1 with anemia, and 1 with erythrocytosis. When results from these 28 samples were excluded, correlations from the remaining nonflagged results (canine/feline) were .63/.65 for neutrophils, .67/.65 for lymphocytes, .11/.33 for monocytes, and .63/.82 for eosinophils. CONCLUSION: Although use of a 100-cell (vs 200-cell) M-diff% may be a limitation of our study, good correlation between WBC differentials obtained using the LaserCyte and the manual method was achieved only for feline eosinophils.     

Staining abnormalities of dermal collagen in eosinophil- or neutrophil-rich inflammatory dermatoses of horses and cats as demonstrated with Masson's trichrome stain

A retrospective study was performed on skin biopsy specimens from horses and cats having eosinophilic granulomas with 'collagen degeneration', eosinophilic skin diseases without 'collagen degeneration' and pyogranulomas without 'collagen degeneration'. Neither the appearance of collagen fibres nor the dominant polymorphonuclear cells, as seen in H & E-stained sections, were predictive of Masson's trichrome findings. Hence, a Masson's trichrome staining abnormality of collagen fibres was no more likely to be present in lesions with 'collagen degeneration' than in those lesions without 'collagen degeneration'. In addition, evaluation of trichrome-stained specimens suggested that there is no collagen degeneration in equine and feline eosinophilic granulomas and that the areas previously referred to as collagen degeneration are more appropriately called flame figures.     

Plasma histamine concentration and histamine detection in peripheral blood eosinophils in cats

Plasma histamine levels were measured in 11 clinically healthy cats and 15 cats with allergic dermatitis. Histamine levels were markedly elevated in 5/15 allergic cats. A calcium ionophore, A23187, stimulates histamine release from feline peripheral blood cells. Immunostaining of blood smears from clinically healthy cats revealed that approximately 10% of eosinophils possessed histamine-containing granules. These results indicate that some peripheral eosinophils in cats contain histamine and can release histamine by appropriate stimulation.     

Myocardial collagen deposition and inflammatory cell infiltration in cats with pre-clinical hypertrophic cardiomyopathy

The histological features of feline hypertrophic cardiomyopathy (HCM) have been well documented, but there are no reports describing the histological features in mild pre-clinical disease, since cats are rarely screened for the disease in the early stages before clinical signs are apparent. Histological changes at the early stage of the disease in pre-clinical cats could contribute to an improved understanding of disease aetiology or progression. The aim of this study was to evaluate the histological features of HCM in the left ventricular (LV) myocardium of cats diagnosed with pre-clinical HCM. Clinically healthy cats with normal (n = 11) and pre-clinical HCM (n = 6) were identified on the basis of echocardiography; LV free wall dimensions (LVFWd) and/or interventricular septal wall (IVSd) dimensions during diastole of 6–7 mm were defined as HCM, while equivalent dimensions <5.5 mm were defined as normal. LV myocardial sections were assessed and collagen content and inflammatory cell infiltrates were quantified objectively. Multifocal areas of inflammatory cell infiltration, predominantly lymphocytes, were observed frequently in the left myocardium of cats with pre-clinical HCM. Tissue from cats with pre-clinical HCM also had a higher number of neutrophils and a greater collagen content than the myocardium of normal cats. The myocardium variably demonstrated other features characteristic of HCM, including arteriolar mural hypertrophy and interstitial fibrosis and, to a lesser extent, myocardial fibre disarray and cardiomyocyte hypertrophy. These results suggest that an inflammatory process could contribute to increased collagen content and the myocardial fibrosis known to be associated with HCM.     

Hypereosinophilic syndrome in cats: a report of three cases.

The clinical, clinicopathological and pathological findings in three cats with hypereosinophilic syndrome are described. The cats chosen for the study had marked eosinophilia and evidence of tissue infiltration by eosinophils. Necropsies were performed on two cats, biopsy and blood samples were provided for the third cat. At necropsy, there was diffuse reddening of femoral bone marrow with ulceration and thickening of the duodenum. The livers had an enhanced lobular pattern with multiple, white, 1-3 mm nodules throughout the parenchyma. One cat had splenomegaly and the other had several enlarged, white, firm lymph nodes. Histopathologically, there was eosinophil infiltration of intestine, lymph nodes, liver, spleen, adrenal medulla and beneath the endocardium. Ultrastructurally, the eosinophils from lymph node and bone marrow of cat II were morphologically normal. The rigid criteria for eosinophilic leukemia were not fulfilled by these cases and the etiology of the eosinophilia in each case is not known. Possible pathogenic mechanisms are discussed.     

Reference intervals for feline cerebrospinal fluid: cell counts and cytologic features

Reference intervals for feline CSF cell counts and cytologic variables were determined. Values were derived from 58 adult cats that had normal neurologic examination findings and did not have histologic lesions of the CNS. Effect of age or gender was not apparent for any CSF variable, and no CSF variable was significantly correlated with its corresponding blood value. Total WBC count and neutrophil and eosinophil percentages were positively correlated with the CSF RBC count. Thus, proposed reference intervals for feline CSF were derived from 33 cats with CSF RBC count of less than 31 cells/ul. Data for CSF samples with range between 31 and 1,700 RBC/microliters were also determined. Erythrocyte count was not significantly different in CSF collected, using 20- or 22-gauge spinal needles.     

Erythrocyte macrocytosis in feline leukemia virus associated anemia

Using erythrocyte volume distribution histograms (erythrograms), erythrocyte macrocytosis and anisocytosis were quantitated in 139 cats tested for feline leukemia virus group-specific antigen. Feline leukemia virus-negative cats with non-regenerative anemia or normal packed cell volumes had normal mean corpuscular volume values. Uninfected cats with regenerative anemia had prominent significantly increased macrocytosis and anisocytosis (p less than 0.01). Ninety percent of 62 feline leukemia virus-positive cats had altered erythrograms. Thirty-three feline leukemia virus-positive cats with non-regenerative anemia had marked macrocytosis. Their mean corpuscular volume values (mean 60 fl +/- 2 fl standard error, reference range of 37-49 fl) were significantly greater than those of feline leukemia virus-negative cats except for those with regenerative anemia. Feline leukemia virus-positive, non-anemic cats had significantly increased mean corpuscular volume values of intermediate magnitude. Nine adult cats experimentally infected with feline leukemia virus developed non-regenerative anemia with significant increases in mean corpuscular volume and anisocytosis. However, the macrocytosis observed in these cats was considerably less than in naturally occurring feline leukemia virus-positive cats with non-regenerative anemia. These observations indicate there are events in the pathogenesis of feline leukemia virus-associated anemia other than simple erythroid hypoplasia. We suggest that hemolysis and erythrocyte regeneration occur before erythroid hypoplasia and may partially account for macrocytosis observed in the face of non-regenerative anemia.     

Evaluation of Felis domesticus allergen I as a possible autoallergen in cats with eosinophilic granuloma complex

OBJECTIVE: To investigate the role of Felis domesticus allergen I (Feld I) in the pathogenesis of eosinophilic granuloma complex (EGC) in cats. ANIMALS: 7 healthy cats and 6 cats with EGC. PROCEDURE: Epidermis was removed from 4 areas. Rubber stoppers filled with Feld I, saline (0.9% NaCl) solution, and PBS solution were glued to the skin lesions and removed 48 hours later. Fluid within each stopper was collected. Biopsy specimens were obtained at each site, snap frozen, and stored at -70 C. Total and differential numbers of cells in fluid were counted. Biopsy specimens were stained by use of monoclonal antibodies against feline CD4, CD8 and CD3. Data were analyzed by use of multivariate repeated-measures analysis. RESULTS: Healthy cats had a significant increase in number of CD3+ cells, compared with number of CD4+ and CD8+ cells, and Feld I caused a significant increase in number of CD3+ cells, compared with PBS or saline solutions. Cats with EGC had a significant increase in number of CD3+ cells, compared with number of CD4+ and CD8+ cells, and Feld I caused a significant increase in number of CD3+ and CD4+ cells, compared with PBS or saline solutions. Cats with EGC had an increased CD4+ response, a significantly decreased CD8+ response, and a significantly increased CD4-to-CD8 ratio compared with healthy cats. CONCLUSIONS AND CLINICAL RELEVANCE: The increased CD4+ response, significantly decreased CD8+ response, and significantly increased CD4-to-CD8 ratio are comparable to results in atopic people and allergic cats. Therefore, Feld I could be an autoallergen responsible for chronic inflammatory reactions in cats with EGC.     

Feline eosinophilic granuloma complex(ities): some clinical clarification

PRACTICAL RELEVANCE: The feline eosinophilic granuloma complex (EGC) comprises a group of clinically well recognised but poorly understood dermatoses that are common in cats. In many cases, lesions are severe and can be accompanied by varying degrees of (and sometimes considerable) pruritus and/or pain. In addition, lesions can be chronic and recurrent. It is, therefore, important to achieve a prompt and accurate diagnosis in order to provide optimal, often life-long, treatment for affected cats. PATIENT GROUP: There is no age predisposition or well documented breed predilection for the development of EGC lesions in cats. Some studies have reported a possible female predisposition, but this has not been consistently documented. CLINICAL CHALLENGES: The clinical diagnosis of EGC lesions is usually straightforward, but investigation of the potential underlying aetiology can pose a challenge for the clinician. Information on the indication for various diagnostic tests and their interpretation is lacking, and the tendency for these cases to be managed with chronic medical intervention prior to achieving a definitive diagnosis can further complicate the interpretation of any diagnostic investigation. In addition, successful therapeutic management of these cases can be challenging. Some cats suffer only a single episode of disease that resolves with treatment, while others have recurrent lesions and some of these can be refractory to treatment. The individual variation in both the clinical nature of the disease and the response to therapy could be related to disease severity, but could also be explained by differences in the underlying aetiopathogenesis. EVIDENCE BASE: This article reviews the published literature to discuss the complex aetiology of the EGC and present an overview of the different clinical presentations and diagnosis. A further and particular aim has been to provide some evidence-based recommendations for the management of this unusual group of dermatoses.     

Granules of blood eosinophils are stained directly by anti-immunoglobulin fluorescein isothiocyanate conjugates

Direct staining of the granules of blood eosinophils by anti-immunoglobulin fluorescein isothiocyanate (FITC) conjugates was observed when feline blood smears were tested for presence of feline leukemia virus (FeLV) antigen by immunofluorescent antibody. When blood smears of other species including swine, horses, cattle, dogs, sheep, birds, and human beings were examined, direct staining of eosinophils by FITC conjugates was also detected. This FITC staining was restricted to eosinophils and was not observed in neutrophils, lymphocytes, and platelets. Direct FITC staining of eosinophils does not represent a problem in immunofluorescent test for the detection of FeLV infection in cats, as long as the eosinophils, which can easily be recognized as such, are excluded from the spectrum of interpreted cells.     

Eosinophilic dermatitis with edema in nine dogs, compared with eosinophilic cellulitis in humans.

A unique eosinophilic dermatitis with edema in dogs is characterized by extremely erythematous coalescing macules and plaques with associated edema, and is similar to eosinophilic cellulitis (Wells' syndrome) in humans. Histopathologic features include a profound eosinophilic dermal infiltrate, focal areas of collagen fiber degeneration surrounded by eosinophils (flame figures), dilated vessels, and dermal edema. Etiopathogenesis is unknown, but a hypersensitivity reaction to medications, arthropod bites, or other foreign antigens is suspected.