Clinical and clinicopathological features and outcomes of cats with suspected dietary induced pancytopenia.

BACKGROUND: After a strong epidemiological link to diet was established in an outbreak of pancytopenia in cats in spring 2021 in the United Kingdom, 3 dry diets were recalled. Concentrations of the hemato- and myelotoxic mycotoxins T-2, HT-2 and diacetoxyscirpenol (DAS) greater than the European Commission guidance for dry cat foods were detected in the recalled diets. OBJECTIVES: To describe clinical and clinicopathological findings in cats diagnosed with suspected diet induced pancytopenia. ANIMALS: Fifty cats presenting with pancytopenia after exposure to a recalled diet. METHODS: Multicenter retrospective case series study. Cats with known exposure to 1 of the recalled diets were included if presented with bi- or pancytopenia and underwent bone marrow examination. RESULTS: Case fatality rate was 78%. Bone marrow aspirates and biopsy examination results were available in 23 cats; 19 cats had a bone marrow aspirate, and 8 cats had a biopsy core, available for examination. Bone marrow hypo to aplasia-often affecting all cell lines-was the main feature in all 31 available core specimens. A disproportionately pronounced effect on myeloid and megakaryocytic cells was observed in 19 cats. Myelofibrosis or bone marrow necrosis was not a feature. CONCLUSION AND CLINICAL IMPORTANCE: Mycotoxin induced pancytopenia should be considered as differential diagnosis in otherwise healthy cats presenting with bi- or pancytopenia and bone marrow hypo- to aplasia.

A feline case of multiple myeloma treated with bortezomib.

BACKGROUND: Multiple myeloma (MM) is an uncommon neoplasm in cats. There is no established standard of treatment due to the rare occurrence of this disease in cats. Bortezomib is a proteasome inhibitor that serves as the first-line drug for MM in humans, but its effectiveness currently is unknown in feline MM. We present here the case report of a feline MM that exhibited a favorable response to bortezomib. CASE PRESENTATION: The case was an 11-year-old non-castrated male domestic cat with light-chain MM presenting with clinical symptoms (anorexia, fatigue, and vomiting), mild azotemia, and pancytopenia. The cat failed on melphalan with prednisolone (MP), so bortezomib (Velcade) was initiated on Day 88. A total of 6 cycles of the treatment was performed, with each treatment cycle consisting of twice-weekly subcutaneous administration for 2 weeks followed by a 1-week rest. The dose of bortezomib was 0.7 mg/m2 for first week and 1.0 mg/m2 for second week in the first cycle. A dose of 0.7 mg/m2 was used for subsequent cycles. Prednisolone was used concomitantly in the first 2 cycles. Following treatment with bortezomib, clinical symptoms disappeared and a decrease in serum globulin and recovery of pancytopenia were noted. A monoclonal gammopathy, overproduction of serum immunoglobulin light chain, and Bence-Jones proteinuria that existed at diagnosis were undetectable on Day 123. A monoclonal gammopathy also was not detectable at the end of the bortezomib treatment (Day 213). Anorexia, fatigue, and marked bone marrow toxicity were experienced when bortezomib was administrated at a dose of 1.0 mg/m2, while no recognizable toxicity was observed at a dose of 0.7 mg/m2 throughout the treatment period. The case was placed on follow-up and there was no evidence of relapse as of Day 243. CONCLUSIONS: Bortezomib was effective and durable for the treatment of this case of feline MM after failure with MP. Bortezomib was well-tolerated in this cat at a dose of 0.7 mg/m2, but not at 1.0 mg/m2. Bortezomib appears to be a drug worthy of further study for the treatment of feline MM.

Nontraumatic hemoabdomen and pancytopenia secondary to myelolipoma in a cat.

OBJECTIVE: (1) To report an unusual etiology for nontraumatic hemoabdomen in cats, and (2) to describe onset and recovery from severe, unexpected pancytopenia seen after surgical removal of a large intra-abdominal myelolipoma. CASE SUMMARY: A 14-year-old neutered male domestic shorthair cat was presented for emergent treatment of suspected nontraumatic hemoabdomen. A hyperechoic mass, with ultrasonographic echogenicity similar to fat, was found in the right cranial abdomen and believed to be associated with the mesentery. Cytological examination of abdominal fluid identified marked extramedullary hematopoiesis within the hemorrhagic effusion. Exploratory laparotomy identified a hepatic mass, which was resected, and revealed to be a hepatic myelolipoma on histopathological examination. The patient's initial recovery was uneventful. However, continued hyporexia resulted in readmission 4 days postoperatively, at which time the patient was found to have a profound, tri-lineage pancytopenia, and cytological evidence indicative of bone marrow recovery. The pancytopenia resolved with continued medical management and supportive care. NEW OR UNIQUE INFORMATION PROVIDED: Ruptured myelolipoma is not a commonly considered differential for nontraumatic hemoabdomen in cats. Furthermore, severe pancytopenia is unexpected following surgical resection of a myelolipoma. This case provides a unique clinical presentation of both nontraumatic hemoabdomen and bone marrow recovery.

Outcome of dogs with bone marrow suppression secondary to Sertoli cell tumour.

Sertoli cell tumours are one of the most common canine testicular neoplasia. These tumours are significantly more likely to arise in cryptorchid dogs and are often functional, oestrogen-secreting tumours which can lead to fatal myelotoxicity. The goal of this study was to describe the outcome of dogs with oestrogen-induced bone marrow suppression secondary to Sertoli cell tumours in seven client-owned dogs. Medical records from April 1, 2011 through April 1, 2021 were reviewed to identify dogs that underwent surgical management of a Sertoli cell tumour with documented bone marrow suppression. Overall, 5/7 dogs required transfusion of blood products peri-operatively. Cases 1 and 6 received a transfusion of packed red blood cells (RBC) prior to surgery and case 5 required a transfusion of whole blood. Case 1 also required a transfusion of platelets before surgery. Post-operatively, cases 1 and 2 received packed RBC's and case 6 received two transfusions of whole blood. Case 3 required transfusions of both fresh frozen plasma and platelets post-operatively. All dogs survived to discharge and 6/7 dogs had documented improvement in haematopoietic values. Two dogs remained chronically thrombocytopenic. The median hospital stay was 4 days. One dog died within 4 weeks of surgery from worsening pancytopenia. Survival for greater than 1 year was documented in 4/7 dogs, and one dog was lost to follow-up 4 months post-operatively. One dog remained severely pancytopenic 4 weeks post-operatively and received oral lithium treatment. Improvements in all blood cell lines were observed within the 4 weeks and resolution of pancytopenia within 6 weeks. Historically, the prognosis for dogs with bone marrow suppression secondary to Sertoli cell tumours was guarded to poor. This report documented improved outcomes for dogs that underwent surgery, including one dog that received lithium chloride as treatment for Sertoli cell tumour-induced bone marrow suppression.

[Acquired transient Fanconi syndrome after feeding jerky treats in dogs - A case series]. / Erworbenes transientes Fanconi-Syndrom nach Fütterung von Trockenfleisch als Leckerchen beim Hund.

Between April 2018 and August 2019, 6 dogs with laboratory diagnostic evidence of Fanconi syndrome were presented to the Tierklinik Hofheim. The presumptive diagnosis was confirmed via urine amino acid analysis in all dogs. In 5 of the 6 dogs an alimentary origin was suspected, in 3 dogs the course of the disease could be followed. Supportive therapeutic measures and elimination of jerky treats from the dogs' diet improved the clinical symptoms in all dogs with known follow-up. This is the first case series of dogs with alimentary acquired Fanconi syndrome in Germany. The frequency of occurrence of the disease in that short period of time in only one small animal clinic suggests a significantly higher incidence than currently assumed.

Persistent infection and pancytopenia associated with ferret systemic coronaviral disease in a domestic ferret.

Ferret systemic coronaviral disease (FSCD) is a well-established cause of mortality in domestic ferrets. We describe herein novel findings in a case of FSCD that was diagnosed and medically managed following virus detection by immunohistochemical (IHC) staining of surgical biopsy samples. Hematologic changes in this ferret suggested spread of the virus to the bone marrow, which was confirmed by IHC staining of a postmortem sample. Genotyping of the virus indicated that the virus grouped with alphacoronaviruses and was most closely related to ferret enteric coronavirus (FRECV) MSU-2. Our clinical case demonstrates that a FRECV MSU-2-like ferret coronavirus associated previously with the enteric pathotype may cause systemic disease, including bone marrow involvement causing persistent pancytopenia.

Bovine Neonatal Pancytopenia-Associated Alloantibodies Recognize Individual Bovine Leukocyte Antigen 1 Alleles.

Bovine neonatal pancytopenia (BNP) was a vaccine-induced alloimmune disease observed in young calves and characterized by hemorrhages, pancytopenia, and severe destruction of the hematopoietic tissues. BNP was induced by alloreactive maternal antibodies present in the colostrum of certain cows vaccinated with a highly adjuvanted vaccine against bovine viral diarrhea. Bioprocess impurities, originating from the production cell line of the vaccine, are likely to have induced these alloreactive antibodies. One prominent alloantigen recognized by vaccine-induced alloantibodies is highly polymorphic bovine major histocompatibility complex class I antigen (bovine leukocyte antigen 1-BoLA I). Aim of this study was to define the fine specificity of BNP-associated anti-BoLA I alloantibodies. In total, eight different BoLA I alleles from the production cell line were identified. All genes were cloned and recombinantly expressed in murine cell lines. Using these cells in a flow cytometric assay, the presence of BoLA I specific alloantibodies in BNP dam sera was proven. Three BoLA I variants were identified that accounted for the majority of vaccine-induced BoLA I reactivity. By comparing the sequence of immunogenic to non-immunogenic BoLA I variants probable minimal epitopes on BoLA I were identified. In general, dams of BNP calves displayed high levels of BoLA I reactive alloantibodies, while vaccinated cows delivering healthy calves had significantly lower alloantibody titers. We identified a subgroup of vaccinated cows with healthy calves displaying very high alloantibody titers. Between these cows and BNP dams no principle difference in the BoLA I reactivity pattern was observed. However, with a limited set of dam-calf pairs it could be demonstrated that serum from these cows did not bind to BoLA I expressing leukocytes of their offspring. By contrast, when testing cells from surviving BNP calves with the corresponding dam's serum there was significant binding. We therefore conclude that predominantly highly alloreactive cows are at risk to induce BNP and it depends on the paternally inherited BoLA I whether or not the calf develops BNP.

High-Dose Filgrastim Treatment of Nonregenerative Pancytopenia Associated With Chronic Canine Ehrlichiosis.

OBJECTIVE: To report the management and outcome of a dog with canine monocytic ehrlichiosis and nonregenerative pancytopenia, with high doses of filgrastim. CASE DESCRIPTION: An 8-year-old male, mixed-breed dog, weighing 5.6kg, presented with a 1-month history of hyporexia, adynamia, and a weight loss of approximately 1kg. The general condition of the dog was observed to be poor as follows: lethargy, tachycardia, marked pallor of the mucous membranes, petechiae on the abdomen, hepatosplenomegaly, and cervical lymphadenopathy. A complete blood count analysis revealed severe leukopenia, thrombocytopenia, and anemia. A direct immunofluorescence assay using anti-Ehrlichia canis-immunoglobin G (1:400) yielded positive result. The dog was diagnosed with nonregenerative pancytopenia associated with canine monocytic ehrlichiosis. The dog presented poor prognostic signs (neutropenia, thrombocytopenia, and severe anemia). The dog was treated with antibiotics and a short course of high-dose filgrastim (50µg/kg, SC, q 48h for 4 days) to stimulate bone marrow response, prednisone to decrease peripheral platelet destruction, and an iron supplement to compensate for the iron deficiency in the bone deposits. Although temporary side effects associated with filgrastim use, such as bone pain, bleeding, and the worsening of thrombocytopenia, were observed, the treatment improved the clinical course and the cell counts in less than a month. CLINICAL RELEVANCE: The treatment protocol used in this case might be an alternative for treating cases of severe myelosuppression. This treatment plan can substantially change the clinical course of the disease for the better, compared to conventional treatment.

Hypocobalaminaemia as a cause of bone marrow failure and pancytopenia in a cat.

CASE REPORT: A male Domestic Short-hair cat was presented for chronic weight loss, lethargy and hyporexia. Complete haematological examination revealed non-regenerative anaemia, neutropenia and thrombocytopenia, as well as Howell-Jolly bodies, anisocytosis, polychromasia and macrocytosis on blood smear evaluation. Histopathological evaluation of bone marrow biopsy disclosed hypocellularity consistent with bone marrow failure. Concurrent hypocobalaminaemia was identified and treated with parenteral cyanocobalamin supplementation. Other differential diagnoses for pancytopenia, including infectious, toxic, immune-mediated and neoplastic causes, were ruled out. CONCLUSION: The cat's erythrocyte, leucocyte and platelet counts normalised after 2 months of cyanocobalamin supplementation, suggesting that pancytopenia may be a rare manifestation of feline cobalamin deficiency.

Bone marrow bi-hypoplasia in a dog with a sertoli cell tumor / Hipoplasia dupla de medula óssea em um cão com tumor de células de sertoli

A 20-year-old unneutered male poodle presented prostration, apathy, staggering gait, lack of appetite and tick infestation. The dog was diagnosed with a Sertoli cell tumor in an undescended testicle by cytological, histopathological and immunohistochemical tests. Pancytopenia with moderate nonregenerative anemia, leukopenia and severe thrombocytopenia were detected in the complete blood count. Cytological and histopathological evaluation of the bone marrow revealed a cellularity of 30%, with erythroid (59%), lymphoid (40%) and mast cells (1%), and an absence of granulocytic, monocytic and megakaryocytic lineage cells. In post-mortem examinations, changes related to hemostatic disorders were found. The absence of microorganisms in molecular tests and an estrogen serum concentration over reference values confirmed hyperestrogenism as a possible cause of pancytopenia. The literature describes a Sertoli cell tumor hyperestrogenism that induced pancytopenia, along with bone marrow hypoplasia of all hematopoietic lineages. In contrast, in the present case, the erythroid precursor cells were preserved in the bone marrow, although there were no reticulocytes circulating in the blood. This case, therefore, should be considered in future investigations of pancytopenia induced by Sertoli cell tumor hyperestrogenism.(AU)

Um cão Poodle, macho, de 20 anos, não castrado, apresentou prostração, apatia, andar cambaleante, falta de apetite e infestação por carrapatos. Nesse animal, foi diagnosticado tumor de células de Sertoli em um testículo não descendente, utilizando-se citologia, histopatologia e imuno-histoquímica. Pancitopenia com anemia moderada não regenerativa, leucopenia e trombocitopenia intensas foram detectadas no hemograma. Na avaliação citológica e histopatológica da medula óssea, havia celularidade de 30%, constituída pelas linhagens eritroide (59%) e linfoide (40%) e por mastócitos (1%), com ausência de células das linhagens granulocítica, monocítica e megacariocítica. Em exames post mortem, mudanças relacionadas à hemostasia foram encontradas. A ausência de micro-organismos nos testes moleculares e a concentração sérica de estrogênio acima dos valores de referência confirmaram hiperestrogenismo como a possível causa da pancitopenia. A literatura descreve hiperestrogenismo em tumores de células de Sertoli induzindo pancitopenia associada com hipoplasia da medula óssea de todas as linhagens hematopoiéticas. Em contraste, no presente caso, as células precursoras eritróides estavam preservadas na medula óssea, embora não houvesse reticulócitos no sangue. Assim, o relato apresentado deve ser considerado em futuras investigações de pancitopenia induzida por hiperestrogenismo em tumor de células de Sertoli.(AU)

The risks of using allogeneic cell lines for vaccine production: the example of Bovine Neonatal Pancytopenia.

INTRODUCTION: Bovine neonatal pancytopenia (BNP) is a hemorrhagic disease that emerged in calves across Europe in 2007. Its occurrence is attributed to immunization of the calf's mother with a vaccine produced using an allogeneic cell line. Vaccine-induced alloantibodies specific for major-histocompatibility class I antigens are transferred from the mother to the calf via colostrum, leading to profound depletion of peripheral blood and bone marrow cells that is often fatal. Areas covered: Pubmed and Web of Science were used to search for literature relevant to BNP and the use of allogeneic vaccine cell lines. Following a review of the pathology and pathogenesis of this novel condition, we discuss potential risks associated with the use of allogeneic vaccine cell lines. Expert commentary: Although BNP is associated with a specific vaccine, it highlights safety concerns common to all vaccines produced using allogeneic cell lines. Measures to prevent similar vaccine-induced alloimmune-mediated adverse events in the future are discussed.

Colostrum from cows immunized with a vaccine associated with bovine neonatal pancytopenia contains allo-antibodies that cross-react with human MHC-I molecules.

In 2006, a new haemorrhagic syndrome affecting newborn calves, Bovine Neonatal Pancytopenia (BNP), was reported in southern Germany. It is characterized by severe bleeding, destruction of the red bone marrow, and a high case fatality rate. The syndrome is caused by alloreactive, maternal antibodies that are ingested by the calf with colostrum and result from a dam vaccination with one particular vaccine against Bovine-Viral-Diarrhoea-Virus. Because bovine colostrum is increasingly gaining interest as a dietary supplement for human consumption, the current study was initiated to elucidate whether BNP alloantibodies from BNP dams (i.e. animals that gave birth to a BNP-affected calf) cross-react with human cells, which could pose a health hazard for human consumers of colostral products. The present study clearly demonstrates that BNP alloantibodies cross-react with human lymphocytes in vitro. In agreement with previous reports on BNP, the cross-reactive antibodies are specific for MHC-I molecules, and sensitize opsonised human cells for in vitro complement lysis. Cross-reactive antibodies are present in serum and colostrum of individual BNP dams. They can be traced in commercial colostrum powder manufactured from cows immunized with the vaccine associated with BNP, but are absent from commercial powder manufactured from colostrum excluding such vaccinated cows. In humans alloreactive, MHC-I specific antibodies are generally not believed to cause severe symptoms. However, to minimize any theoretical risk for human consumers, manufacturers of bovine colostrum for human consumption should consider using only colostrum from animals that have not been exposed to the vaccine associated with BNP.

Reproduction of bovine neonatal pancytopenia (BNP) by feeding pooled colostrum reveals variable alloantibody damage to different haematopoietic lineages.

Bovine neonatal pancytopenia (BNP) is a recently described haemorrhagic disease of calves characterised by thrombocytopenia, leucopenia and bone marrow depletion. Feeding colostrum from cows that have previously produced a BNP affected calf has been shown to induce the disease in some calves, leading to the hypothesis that alloantibodies in colostrum from dams of affected calves mediate destruction of blood and bone marrow cells in the recipient calves. The aims of the current experimental study were first to confirm the role of colostrum-derived antibody in mediating the disease and second to investigate the haematopoietic cell lineages and maturation stages depleted by the causative antibodies. Clinical, haematological and pathological changes were examined in 5 calves given a standardised pool of colostrum from known BNP dams, and 5 control calves given an equivalent pool of colostrum from non-BNP dams. All calves fed challenge colostrum showed progressive depletion of bone marrow haematopoietic cells and haematological changes consistent with the development of BNP. Administration of a standardised dose of the same colostrum pool to each calf resulted in a consistent response within the groups, allowing detailed interpretation of the cellular changes not previously described. Analyses of blood and serial bone marrow changes revealed evidence of differential effects on different blood cell lineages. Peripheral blood cell depletion was confined to leucocytes and platelets, while bone marrow damage occurred to the primitive precursors and lineage committed cells of the thrombocyte, lymphocyte and monocyte lineages, but only to the more primitive precursors in the neutrophil, erythrocyte and eosinophil lineages. Such differences between lineages may reflect cell type-dependent differences in levels of expression or conformational nature of the target antigens.

Clinical and magnetic resonance imaging (MRI) findings of idiopathic aplastic pancytopenia in a dog treated with cyclosporine and azathioprine.

A dog was referred for pancytopenia. Bone marrow biopsy showed hypocellular fatty marrow. Magnetic resonance imaging had a high signal on T1-weighted image in the metaphyseal region of the femur. We suggest that MRI could be a valuable supportive diagnostic method and introduce a strategy of treatment with cyclosporine and azathioprine in canine aplastic pancytopenia.

Bovine Neonatal Pancytopenia: is this alloimmune syndrome caused by vaccine-induced alloreactive antibodies?

Bovine Neonatal Pancytopenia (BNP) is a new emerging disease observed since 2007 in Germany and neighbouring countries. The syndrome affects newborn calves and is characterized by pancytopenia, severe bleeding and high lethality. So far, a causative role of infectious or toxic agents has been ruled out. Instead, the syndrome is induced after ingestion of colostrum, the first milk that supplies the calf with maternal antibodies. In analogy to similar diseases in humans it has therefore been postulated that BNP is caused by alloreactive, maternal antibodies. There is a striking association between BNP and a previous vaccination of the respective dams with a particular vaccine against Bovine Virus Diarrhoea (BVD). This association has led to a suspension of the marketing authorisation for the vaccine, by the European Commission. The current study investigates the role of this vaccine in the pathogenesis of BNP. By flow cytometry we were able to demonstrate that sera of BNP dams (dams that gave birth to a BNP calf) harbour alloreactive antibodies binding to surface antigens on bovine leukocytes. A significantly weaker alloreactivity was observed with sera of non-BNP dams that have been vaccinated with the same vaccine but delivered healthy calves. No binding was seen with non-BVD-vaccinated control cows and animals that were vaccinated with other inactivated BVD vaccines so far not associated with BNP. The binding is functionally relevant, because opsonization of bovine leukocytes with alloantibodies led to an elevated cytophagocytosis by bovine macrophages. To test whether the vaccine induces alloreactive antibodies two strategies were employed: Guinea pigs were vaccinated with a panel of commercially available BVD-vaccines. Only the incriminated vaccine induced antibodies binding surface antigens on bovine leukocytes. Additionally, two calves were repeatedly vaccinated with the suspected vaccine and the development of alloreactivity was monitored. In dependence of the number of booster immunizations the induction of alloreactive antibodies could be observed. Finally, by affinity purification we were able to directly demonstrate that BNP associated alloantibodies cross react with the bovine kidney cell line used for vaccine production. Together this provides strong evidence that this particular BVD vaccine has the potential to induce BNP associated alloantibodies.

Hemophagocytic syndrome in a pancytopenic simian retrovirus-infected male rhesus macaque (Macaca mulatta).

Hemophagocytic syndrome (HPS) is a macrophage hyperactivation disorder triggered by disrupted T-cell macrophage cytokine interaction. HPS has been reported in humans, dogs, cats, and cattle, and it is infrequent and poorly characterized in animals. A 16-year-old male rhesus macaque was euthanized because of severe pancytopenia, including nonregenerative anemia (hematocrit = 5.5%), neutropenia (0.29 K/µl), and thrombocytopenia (21 K/µl). Bone marrow was hypocellular with normal maturation, myeloid hypoplasia, and few megakaryocytes. There were numerous morphologically normal macrophages (12% of nucleated cells), with 6% of nucleated cells being hemophagocytic macrophages in the bone marrow. Serology was negative, but polymerase chain reaction and immunohistochemistry were positive for simian retrovirus type 2. Blood and bone marrow findings were consistent with HPS. Cytopenias are common in simian retrovirus-infected macaques, but HPS has not been reported. An association between simian retrovirus infection and HPS is undetermined, but retrovirus-associated HPS has been observed in humans.

Bone marrow aplasia with pancytopenia and hemorrhage in a Japanese Black calf.

Severe leukopenia was incidentally found in a newborn Japanese Black calf by blood testing during the clinical trial of an iron dextran drug (day 1). At that time, no clinical problems were observed. On day 15, the calf presented with a high rectal temperature and tachypnea. Treatment with antibiotics and non-steroidal anti-inflammatory drugs did not improve clinical signs. Anemia, melena, and prolonged bleeding were also recorded. Necropsy findings revealed subcutaneous petechial hemorrhage and severe bone marrow aplasia. This is the first confirmed case of pancytopenia and hemorrhage associated with bone marrow aplasia in a Japanese Black calf.

Bacillary angiomatosis in an immunosuppressed dog.

A dog being treated with immunosuppressive doses of prednisone and azathioprine for pancytopenia of unknown origin, developed, over a 2-week period, multiple erythematous nodular lesions in the skin including footpads. Skin samples revealed lesions identical to those of human bacillary angiomatosis (BA). The nodules were composed of multifocal proliferations of capillaries, each lined by protuberant endothelial cells. The capillary clusters were separated by an oedematous connective tissue, lightly infiltrated with degenerate inflammatory cells, including neutrophils and macrophages. Tissue sections stained with Warthin-Starry silver stain revealed large numbers of positively stained bacilli in the stromal tissue, most heavily concentrated around the proliferating capillaries. Lesions of vascular degeneration and inflammation were evident. Bartonella vinsonii subsp. berkhoffii genotype 1 was independently amplified and sequenced from the blood and the skin tissue. The pathognomonic nature of the histological lesions, demonstration of compatible silver-stained bacilli in the tissue, and identification of B. vinsonii subsp. berkhoffii in the blood and tissue indicates that this is most likely the aetiologic agent responsible for the lesions. Antibiotic therapy was successful in resolving the nodules. It would appear that B. vinsonii subsp berkhoffii, like Bartonella henselae and Bartonella quintana, has the rare ability to induce angioproliferative lesions, most likely in association with immunosuppression. The demonstration of lesions identical to those of human BA in this dog is further evidence that the full range of clinical manifestations of human Bartonella infection occurs also in canines.