Treatment of canine idiopathic immune-mediated haemolytic anaemia with mycophenolate mofetil and glucocorticoids: 30 cases (2007 to 2011)

Methylprednisolone alone or combined with cyclosporine or mycophenolate mofetil for the treatment of immune-mediated hemolytic anemia in dogs, a prospective study

BACKGROUND

Benefit of adding a second-line immunosuppressive drug to glucocorticoids for the treatment of non-associative immune-mediated hemolytic anemia (naIMHA) in dogs has not been defined prospectively.

HYPOTHESIS/OBJECTIVES

Evaluate the effectiveness of different immunosuppressive protocols in naIMHA dogs.

ANIMALS

Forty-three client-owned dogs.

METHODS

Open label, randomized, clinical trial. Dogs were treated with methylprednisolone (M-group), methylprednisolone plus cyclosporine (MC-group) or methylprednisolone plus mycophenolate mofetil (MM-group). Dogs were defined as responders by disappearance of signs of immune-mediated destruction and hematocrit stabilization. Frequency of responders was compared between M-group and combined protocols (MC and MM-group evaluated together), and among the 3 different therapeutic groups at 14 (T14), 30 (T30), 60 (T60) days after admission. Frequency of complications, length of hospitalization and relapse were also compared. Death rate was evaluated at discharge, T60 and 365 (T365) days.

RESULTS

Proportion of responders was not significantly different between M-group and combined protocols (MC and MM-groups), nor among the 3 therapeutic groups at T14, T30, and T60 (P > .17). Frequency of relapse, complications, and length of hospitalization were not significantly different between M-group and dogs treated with combined protocols, nor among the 3 treatment groups (P > .22). Death was significantly more common only for MM-group compared with MC-group at T60 (+42.8%; 95% CI: 11.5-67.4; P = .009), and at T365 (+50%; 95% CI: 17.5-73.2; P = .003).

CONCLUSIONS AND CLINICAL IMPORTANCE

Combined immunosuppressive therapy did not improve hematological response in naIMHA.

The effects of food on the pharmacokinetics of mycophenolate mofetil in healthy horses

Additional immunomodulatory treatment is needed for the management of immune-mediated disease in horses. Mycophenolate mofetil (MMF) is an immunomodulatory agent used in human and veterinary medicine for the prevention of graft rejection and the management of autoimmune diseases. Few studies exist investigating the pharmacokinetics of MMF in horses. The aim of this study was to evaluate the pharmacokinetics of a single dose of MMF in healthy horses in the fed vs. fasted state. Six healthy Standardbred mares were administered MMF 10 mg/kg by a nasogastric (NG) tube in a fed and fasted state. A six-day washout period was performed between the two doses. No statistically significant differences in mycophenolic acid (MPA) concentrations were seen at any time point apart from 8 h, when plasma metabolite concentrations were significantly higher in the fasted state compared to the fed state (p = .038). Evidence of enterohepatic recirculation was seen only in the fasted state; this did not yield clinical differences in horses administered a single-dose administration but may be significant in horses receiving long-term MMF treatment.

Immune-Mediated Hemolytic Anemia and Clinically Suspected Acute Pancreatitis in Dogs, a Pilot Study

Acute pancreatitis can be a complication of massive hemolysis, above all when intravascular in nature. Therefore, the aim of this study was to investigate the association between canine immune mediated hemolytic anemia (IMHA) and clinically suspected acute pancreatitis (CSAP) and the role of calculated free plasma hemoglobin (Hbfp) in CSAP occurrence/development. In this cohort study the records of 95 dogs with IMHA and 95 sick dogs with pathologies other than IMHA were compared for CSAP occurrence/development. At presentation, 12/95 dogs with IMHA met criteria for CSAP, while only 3/95 sick control dogs met these criteria (χ2 =1.58, P = .008). Within 7 days of hospitalization 9 additional dogs with IMHA had developed CSAP. The Hbfp was calculated and compared for dogs with IMHA that had/developed CSAP and for those without CSAP. In dogs with IMHA, a calculated Hbfp concentration ≥ 0.08 g/dL resulted in an increased relative risk (RR) of having/developing CSAP (RR = 2.54, 95% CI, 1.51-4.29; P = .003). No significant effect on short-term prognosis in dogs with IMHA was found between those having/developing CSAP and those without CSAP. This study showed that dogs with IMHA have an increased risk of having CSAP and Hbfp concentration may be involved in the pathogenesis of acute pancreatitis.

Pharmacokinetics and tolerability of multiple-day oral dosing of mycophenolate mofetil in healthy horses

BACKGROUND

Additional efficacious immunomodulatory treatment is needed for the management of immune-mediated disease in horses. Mycophenolate mofetil (MMF) is an immunosuppressive drug that warrants assessment as a viable therapeutic agent for horses.

HYPOTHESIS/OBJECTIVES

To evaluate the pharmacokinetics (PK) of multiple-day oral dosing of MMF in healthy horses and to determine the tolerability of this dosing regimen.

ANIMALS

Six healthy Standardbred mares.

METHODS

Horses received MMF 10 mg/kg PO q12h for 7 days in the fed state. Serial sampling was performed over 12 hours on Days 1 and 7 with trough samples collected every 24 hours, immediately before morning drug administration. Noncompartmental PK analyses were performed to determine primary PK parameters, followed by calculation of geometric means and coefficients of variation. A CBC, serum biochemical profile, physical examination, and fecal scoring were used to assess dose tolerability.

RESULTS

Seven days of treatment resulted in a mycophenolic acid (MPA) area under the curve (AUC0-12 ) of 12 594 h × ng/mL (8567-19 488 h × ng/mL) and terminal half-life (T1/2 ) of 11.3 hours (7.5-15.9 hours), yielding minor metabolite accumulation in all horses treated. Salmonellosis was detected in the feces of 2 horses by Day 7, and all horses developed myelosuppression, hyperbilirubinemia, hyporexia, decreased gastrointestinal motility, and decreased fecal output by the seventh day of treatment.

CONCLUSION AND CLINICAL IMPORTANCE

Administration of MMF at 10 mg/kg PO q12h resulted in hematologic and clinical toxicity within 1 week of treatment. A decreased MMF dose, frequency, or both is needed to avoid colic. Drug monitoring should include frequent hemograms, serum biochemical profiles, and strict biosecurity protocols.

Retrospective analysis of immunosuppressive and anti-thrombotic protocols in nonassociative immune mediated hemolytic anemia in dogs

BACKGROUND

Evidence supporting the effectiveness of therapeutic protocols for nonassociative immune-mediated hemolytic anemia (na-IMHA) is weak.

HYPOTHESIS/OBJECTIVES

Investigate the efficacy of various drugs in na-IMHA.

ANIMALS

Two hundred forty-two dogs.

METHODS

Multi-institutional retrospective study (2015-2020). Immunosuppressive effectiveness was determined by time to packed cell volume (PCV) stabilization and duration of hospitalization through analysis by mixed model linear regression. Occurrence of disease relapse, death, and antithrombotic effectiveness, were analyzed using mixed model logistic regression.

RESULTS

Use of corticosteroids vs a multi-agent protocol had no effect on time to PCV stabilization (P = .55), duration of hospitalization (P = .13), or case fatality (P = .06). A higher rate of relapse (P = .04; odds ratio: 3.97; 95% confidence interval [CI]: 1.06-14.8) was detected in dogs receiving corticosteroids (11.3%) during follow-up (median: 28.5 days, range: 0-1631 days) compared to multiple agents (3.1%) during follow up (median: 47.0 days, range: 0-1992 days). When comparing drug protocols, there was no effect on time to PCV stabilization (P = .31), relapse (P = .44), or case fatality (P = .08). Duration of hospitalization was longer, by 1.8 days (95% CI: 0.39-3.28 days), for the corticosteroid with mycophenolate mofetil group (P = .01) compared to corticosteroids alone. Use of clopidogrel vs multiple agents had no effect on development of thromboses (P ≥ .36).

CONCLUSIONS AND CLINICAL IMPORTANCE

Addition of a second immunosuppressive agent did not alter immediate outcome measures but might be associated with a reduction in relapse. Use of multiple antithrombotic agents did not reduce incidence of thrombosis.

Successful Treatment With Prednisolone and Mycophenolate Mofetil in a Dog With Recurrent Erythema Multiforme Minor

A 3-year-old neutered male miniature poodle dog was referred with a 19-month history of unresolved dermatological signs despite long-term treatment. On physical examination, the dog had severe multifocal erythematous non-blanching patches and scales in the ventral trunk. Dermatological examination revealed Malassezia infection. Considering the history, clinical signs, and degree of infection, the possibility of a drug eruption appeared higher than that of Malassezia dermatitis. Therefore, bathing in lukewarm water was performed for 4 weeks without any other treatment, but there was no improvement. Subsequently, treatment for Malassezia dermatitis and differentiation from allergic dermatitis were performed, but there was still no improvement. A biopsy was performed, with the histopathology revealing lymphocytic interface dermatitis with keratinocyte apoptosis. Based on the histopathologic evaluation and clinical signs, the dog was diagnosed with erythema multiforme (EM) minor. Immunosuppressive therapy with prednisolone (1 mg/kg PO, twice daily) was initiated and had a good therapeutic effect. However, the lesion recurred after tapering the prednisolone dose (0.5 mg/kg PO, every other day). Therefore, steroid-sparing agents were added to the prednisolone regimen. Ciclosporin, azathioprine, and human intravenous immunoglobulin were administered in combination with prednisolone. Yet again, the lesion recurred when the dose of prednisolone was tapered to 0.5 mg/kg once daily. Mycophenolate mofetil (20 mg/kg PO, twice daily) was then added to the immunosuppressive regimen as a steroid-sparing agent, and complete remission was achieved and maintained even when the dose of prednisolone was tapered to 0.5 mg/kg every other day. This is the first reported case of recurrent EM successfully treated with a combination of prednisolone and mycophenolate mofetil, and this treatment option should be considered for recurrent EM.

Noncompartmental pharmacokinetics of three intravenous mycophenolate mofetil concentrations in healthy Standardbred mares

BACKGROUND

Mycophenolate mofetil (MMF) is the prodrug of mycophenolic acid (MPA) which acts as an immunosuppressive agent. During the biotransformation of MMF to MPA, additional metabolites including MPA phenol glucuronide (MPAG), MPA acyl glucuronide (AcMPAG) and MPA phenol glucoside (MPG) are formed.

OBJECTIVE

To define the noncompartmental pharmacokinetic (PK) parameters of three single doses of intravenous (i.v.) MMF and its downstream metabolites in healthy horses.

ANIMALS

Six healthy Standardbred mares.

MATERIALS AND METHODS

Generic MMF (Par Pharmaceuticals; Chestnut Ridge, NY, USA) was reconstituted and administered as a single i.v. bolus at 1.0 mg/kg, 5.0 mg/kg and 10.0 mg/kg with an eight day washout between treatments. Blood samples were collected immediately before MMF administration and over 24 h. A liquid chromatography-tandem mass spectrometry assay was developed following FDA guidance to determine plasma MMF, MPA, MPAG, AcMPAG and MPG concentrations. Plasma concentrations were analysed independently, followed by calculation of geometric mean and coefficient of variation.

RESULTS

Noncompartmental PK parameters were determined for MMF and all metabolites at all doses. MMF was rapidly converted to MPA in all horses. Each incremental dose of MMF resulted in increases in C_max and AUC_inf _obs for MPA and the three additional metabolites. Within the 10-fold dose range, the increase in C_max and AUC_inf _obs for MMF and its metabolites was nonlinear.

CONCLUSIONS AND CLINICAL RELEVANCE

Horses biotransform MMF into MPA, MPAG, AcMPAG and MPG via the glucuronidation and glucosidation clearance pathways. Equine reference PK profiles for MPA and the metabolites, MPAG, AcMPAG and MPG were established.

Cross-sectional study of approaches to diagnosis and management of dogs with immune-mediated haemolytic anaemia in primary care and referral veterinary practices in the United Kingdom

OBJECTIVES

To determine whether veterinarians in primary care practices (PCPs) and board-certified clinicians (BCCs) approach treatment of dogs with immune-mediated haemolytic anaemia (IMHA) similarly, and whether practitioners with more experience treat similarly to those with less experience. We hypothesised those in PCPs would show more variation in their approach to similar cases than BCCs.

METHODS

A cross-sectional study was conducted by distributing a questionnaire to BCCs and veterinarians in PCPs. The questionnaire included direct questions and a number of clinical scenarios intended to capture approaches to common treatment problems.

RESULTS

Questionnaire responses were received from 241 veterinarians, including 216 in PCPs and 25 BCCs. Veterinarians in both settings used similar tests for diagnosis of IMHA, but BCCs performed more tests to exclude underlying causes of 'associative' disease. All veterinarians reported use of similar initial dosages of glucocorticoids (median 2 mg/kg per day in both groups, p = 0.92) but those used by more experienced practitioners were higher than those with less experience. Most veterinarians made allowances for the weight of dogs, using lower prednisolone dosages in a clinical scenario involving a 40 kg dog compared to a 9 kg dog (p = 0.025 for PCP, p = 0.002 for BCC). BCCs reported greater use of combinations of immunosuppressive drugs (p<0.0001) and of antithrombotic drugs (p<0.0001); use of antithrombotic drugs was also less common among more experienced practitioners compared to less experienced.

CONCLUSIONS

Approaches to treatment of dogs with IMHA differ between BCCs and those in PCP. These differences may affect design and implementation of future research studies and clinical guidelines.

A retrospective study of adverse effects of mycophenolate mofetil administration to dogs with immune-mediated disease

Background

Information regarding adverse events (AEs) of mycophenolate mofetil (MMF) is limited.

Objectives

To evaluate the types and frequency of potential AEs of MMF in dogs with immune‐mediated disease.

Animals

One hundred thirty‐one dogs treated with MMF for management of suspected immune‐mediated disease.

Methods

Retrospective study. Medical records were reviewed to find and group suspect AEs in gastrointestinal (GI), hematologic, and other categories. Age, dosage, body weight, and sex were analyzed between dogs with and without AEs by using the Mann‐Whitney U‐test and chi‐squared test.

Results

The median starting dosage of MMF was 17.5 mg/kg/day (interquartile range [IQR] = 15.1‐20.6 mg/kg/day) and the median treatment duration was 56 days (IQR = 14‐236 days). Mycophenolate mofetil was prescribed for immune‐mediated hemolytic anemia (n = 31), immune‐mediated thrombocytopenia (n = 31), pemphigus foliaceus (n = 15), immune‐mediated polyarthritis (n = 12), and others (n = 42). Overall, potential AEs of MMF were observed in 34 of 131 dogs (GI 24.4% [31/127], neutropenia 4% [3/76], anemia 4% [1/25], thrombocytopenia 4.0% [1/25], and dermatologic 1.5% [2/131]). There were no significant differences among dogs with (n = 37) or without potential AEs (n = 94) in regards to sex, age, body weight, or dosage of MMF (P = .06, .13, .24, and .26, respectively).

Conclusions and Clinical Importance

In the dogs administered MMF, GI AEs were most common. Since potential hematologic and dermatologic AEs developed in a few dogs, clinicians should be aware of these when prescribing MMF to dogs with immune‐mediated disease.

Successful Treatment of Mucocutaneous Lupus Erythematosus in a Dog with Prednisolone, Mycophenolate Mofetil and Tacrolimus

A 6-year-old, intact male miniature Pinscher dog had erosive lesions on perilabial, peripenial and perianal mucocutaneous areas, which were exacerbated by ulcerations, crusts, with pain while defecating and urinating. The lesions were symmetrical, and no systemic signs were observed. Histopathological evaluation showed parakeratotic hyperkeratosis, ulceration and cell-rich lymphoplasmacytic interface dermatitis with basal keratinocyte apoptosis. Immunohistochemistry revealed strong reaction in the dermoepidermal junction against goat-canine IgG and mild-to-moderate reaction against goat-canine IgA, IgM and C3. Based on these findings, the dog was diagnosed with mucocutaneous lupus erythematosus (MCLE). Oral prednisolone 1 mg/kg twice daily, mycophenolate mofetil (MMF) 18.3 mg/kg twice daily and 0.1% tacrolimus ointment were prescribed as initial treatment. The lesions showed remarkable improvement within 4 weeks, but the dog exhibited polyuria, polydipsia and hepatomegaly with high dosage of prednisolone. Hence, the dosage of prednisolone was gradually tapered for 9 weeks and discontinued, but MMF and tacrolimus were continued. No new lesion or associated side effect was observed while reducing the MMF dose to 10 mg/kg twice daily and with continuous use of tacrolimus ointment after steroid discontinuation. In conclusion, this case report emphasizes the usefulness of MMF and tacrolimus as steroid-sparing agents in the treatment of dogs with MCLE. To the best of our knowledge, this is the first case report of MCLE that was successfully managed long-term with MMF and tacrolimus.

Thromboelastometry assessment of mycophenolate mofetil effect on thrombotic risk in dogs with primary and secondary immune-mediated hemolytic anemia and by Erhlichia canis infection

ABSTRACT This study aimed to identify, by means of thromboelastometry assessment, altered thrombotic risk in dogs with primary and secondary IMHA by E. canis infection after initiating the immunosuppressive therapy with mycophenolate mofetil. The animals’ screening was based on complete blood count (CBC), biochemical and urine tests. Dogs with moderate to severe anemia (hematocrit ≤ 25%) which showed symptoms of immune-mediated hemolysis, such as spherocytosis, positive saline agglutination, bilirubinuria and/or hemoglobinuria, were included. Blood and urine samples were collected at two different moments. The first sample (M1) was collected at the time of diagnosis, when hematocrit was lower or equal to 25% before treatment with mycophenolate mofetil (Accord ®); the second sample (M2) was collected after treatment with mycophenolate mofetil, when hematocrit was greater or equal to 30%. Five out of the twelve animals selected died before the end of the study. No reduction in thrombotic risk was observed in the animals treated with mycophenolate mofetil. The animals that presented hypocoagulation at the time of diagnosis showed the worst prognosis, and their reticulocyte count displayed a better prognostic value than their erythrocytes count at the time of diagnosis.

Evaluation of membrane-based therapeutic plasma exchange as adjunctive treatment for immune-mediated hematologic disorders in dogs

Background

Therapeutic plasma exchange (TPE) has been used increasingly to treat immunological diseases in dogs, although data concerning its efficacy are lacking.

Hypothesis/Objectives

To describe the clinic and the outcome of dogs with immune‐mediated hematological disorders (IMHD) treated with membrane filtration TPE.

Animals

One hundred forty‐six dogs diagnosed with IMHD, including 17 dogs treated with and 129 control dogs treated without TPE.

Methods

Retrospective study of cases selected with a search of all medical records for dogs diagnosed with IMHD (2010‐2019). Primary outcomes included the assessment of safety and efficacy of adjunctive TPE compared to medical treatment alone.

Results

The TPE group included 7 dogs with immune‐mediated hemolytic anemia (IMHA), 5 dogs with immune‐mediated thrombocytopenia (IMT), and 5 dogs with combined IMHA‐IMT; the control group included 63 dogs with IMHA, 47 dogs with IMT, and 19 dogs with IMHA‐IMT. Dogs treated with TPE were more often refractory to initial immunosuppression (71%) than controls (43%; P = .04). Complications were observed in 15/43 TPE treatments (35%). The response rate of dogs treated with TPE was 83% in IMHA (controls, 65%; P = .5) and 80% in IMT (controls, 70%; P = .71). Overall, 12/17 dogs (71%) treated with TPE reached complete remission, 2/17 (12%) partial remission, and 3/17 (18%) died or were euthanized. Eighty‐two percent of the dogs treated with TPE survived to discharge (controls, 69%; P = .4).

Conclusions and Clinical Importance

Despite a bias toward dogs refractory to initial immunosuppression, dogs treated with adjunctive TPE had a similar outcome as dogs treated medically.

Therapeutic Strategies for Treatment of Immune-Mediated Hemolytic Anemia

Immune-mediated hemolytic anemia is a common hematologic disorder in dogs. Disease management involves immunosuppression using glucocorticoids, potentially in combination with other medications such as azathioprine, cyclosporine, or mycophenolate mofetil. Therapeutic drug monitoring may enhance the utility and maximize the safety of cyclosporine and mycophenolate mofetil. The disease is proinflammatory and prothrombotic. Antithrombotic drug administration is therefore essential, and anticoagulant therapy should be initiated at the time of diagnosis. Additional therapies include red blood cell transfusion to support blood oxygen content. Future therapies may include therapeutic plasma exchange, anti-CD20 monoclonal antibodies, and complement inhibitors.

Evaluating the use of cytosine arabinoside for treatment for recurrent canine steroid-responsive meningitis-arteritis

BACKGROUND

Relapses in steroid-responsive meningitis-arteritis (SRMA) are frequently observed but specific treatment protocols to address this problem are sparsely reported. Standard treatment includes prolonged administration of glucocorticoids as monotherapy or in combination with immunosuppressive drugs. The aim of this study was to assess the safety and efficacy of cytosine arabinoside (CA) in combination with glucocorticoids for treatment of SRMA relapses in 12 dogs on a retrospective basis.

METHODS

Dogs with recurrent episodes of SRMA and treated with a combination of CA and prednisolone were included. Information about clinical course, treatment response and adverse events was collected from medical records. Ethical approval was not required for this study.

RESULTS

Ten dogs (10/12) responded well to the treatment with clinical signs being completely controlled. One dog is in clinical remission, but still under treatment. One dog (8%) showed further relapse. Mean treatment period was 51 weeks. Adverse events of variable severity (grade 1-4/5) were documented in all dogs during treatment according to the veterinary cooperative oncology group grading. Three dogs developed severe adverse events. Laboratory findings showed marked changes up to grade 4. Diarrhoea and anaemia were the most often observed adverse events (6), followed by dermatitis (4), alopecia (3) and pneumonia (3). Including blood chemistry changes (13), 50 adverse events were found in total.

CONCLUSION

Treatment with CA and glucocorticoids resulted in clinical remission in 10/12 dogs, but a high incidence of adverse events occurred requiring additional measures. All adverse events could be managed successfully in all cases.

Evaluation of treatment with a combination of mycophenolate mofetil and prednisolone in dogs with meningoencephalomyelitis of unknown etiology: a retrospective study of 86 cases (2009-2017)

BACKGROUND

Combination therapy with glucocorticoids and adjunctive immunomodulating drugs has been generally accepted as a standard treatment regimen for meningoencephalomyelitis of unknown etiology (MUE). We hypothesized that treatment with MMF as an adjunctive agent along with glucocorticoids would be effective and well-tolerated protocol in dogs with MUE. Eighty-six dogs with MUE between May 2009 and June 2017 were included (59 females and 27 males; mean age of 5.93 years; mean body weight of 3.83 kg). The medical records of dogs with MUE treated with prednisolone and MMF were retrospectively evaluated to determine the therapeutic response, survival time, and treatment-related adverse effects.

RESULTS

A partial or complete response (CR) was recorded for 75 dogs. The overall median survival time from the initiation of treatment was 558 days. Dogs that showed CR with no relapse over the treatment period (from diagnosis to death) had significantly longer median survival times. A significantly higher mortality hazard ratio of 4.546 was recorded in dogs that failed to achieve CR. The interval between the onset of clinical signs and the clinical presentation was not significantly associated with CR, relapse rate, and survival time. Adverse effects included gastrointestinal upsets in 26 dogs (30.23%), sporadic infections in 17 dogs (19.77%), and pancreatitis in seven dogs (8.14%).

CONCLUSIONS

The results suggest that adjunctive MMF treatment for MUE is safe and comparable to other immunosuppressive protocols. The treatment should focus on the achievement of CR and preventing relapse for successful management.

Suspected hepatopathy and pancreatitis associated with mycophenolate mofetil use in a cat with immune-mediated haemolytic anaemia

Case summary

A 5-year-old spayed female domestic shorthair cat was referred for severe anaemia. Findings on initial work-up were consistent with a diagnosis of idiopathic immune-mediated haemolytic anaemia. A combination of prednisolone and mycophenolate mofetil (MMF) was instituted. On revisit approximately 2 months later, red blood cell parameters were normal, but the plasma was described as icteric, prompting further investigation. Concurrent hepatopathy and pancreatitis were diagnosed, suspected as being adverse reactions to MMF, as has been reported with use of the drug in humans. Resolution of serum biochemistry abnormalities took approximately 2 months, following discontinuing MMF. At the time of writing, the cat remained clinically well 1 year after initial presentation.

Relevance and novel information

With increasing use of MMF as an immunosuppressive agent in cats, clinicians should be aware of both common and potentially rare adverse effects, such as those described herein. In addition, suitable monitoring tools need to be in place to facilitate early detection and appropriate management.

Primary immune-mediated haemolytic anaemia: a retrospective long-term study in 61 dogs

OBJECTIVES

The objective of this study is to describe the course of disease of dogs with primary immune-mediated haemolytic anaemia (pIMHA) with an observation period longer than 90 days in regard to clinical signs, laboratory results and treatment response.

MATERIAL AND METHODS

Clinical records between January 2003 and December 2011 were reviewed. Diagnosis of pIMHA was based on the presence of haemolytic anaemia with a packed cell volume of <0.35 L/L, a positive Coombs' test and/or erythrocyte agglutination, spherocytosis and exclusion of an underlying disease. Included were dogs which could be monitored for more than 90 days after initial presentation.

RESULTS

Sixty-one dogs with pIMHA were included. The initial packed cell volume ranged from 0.08 to 0.30 L/L (median 0.16). Immunosuppressive treatment included prednisolone in all the cases; 32 dogs successively received cyclosporine (28), cyclophosphamide (5), leflunomide (2) or human intravenous immunoglobulins (2) in addition. In 33/61 dogs, the drugs were discontinued 67-3372 days (median 334) after beginning of therapy; in 28 dogs, the drug dosage was reduced, but not discontinued until the end of the study. Three dogs developed immune-mediated thrombocytopenia (days 132, 156 and 680). The observation period ranged from 96 to 4147 days (median 628). A total of 22.9% (14/61) of the dogs developed a relapse after 94-3972 days (median 517). Five dogs were euthanased due to a relapse after 96-1188 days (median 628).

CLINICAL SIGNIFICANCE

Long-term prognosis in dogs with pIMHA is favourable. However, a relapse can occur after many years. Relapse was the most common cause of death in dogs with pIMHA that survive more than 90 days.

Pharmacokinetics of mycophenolic acid and its effect on CD4+ and CD8+ T cells after oral administration of mycophenolate mofetil to healthy cats

Background

Mycophenolate mofetil (MMF) is an immunosuppressant used in human and veterinary medicine. Little pharmacokinetic and pharmacodynamic information on MMF is available in cats.

Objective

To evaluate the plasma disposition of mycophenolic acid (MPA) and assess its effect on total peripheral blood mononuclear cells and CD4⁺/CD8⁺ ratios after PO administration of MMF.

Animals

Healthy cats (n = 10).

Methods

Mycophenolate mofetil was administered at a dosage of 10 mg/kg q12h (n = 3), 15 mg/kg q12h (n = 3), and 15 mg/kg q8h (n = 4) for 7 days. Concentrations of MPA and derivatives were determined using ultra‐high‐performance liquid chromatography. Flow cytometry was used to assess CD4⁺/CD8⁺ T‐cell ratios.

Results

All cats biotransformed MMF into MPA. Half of the cats (5/10) had adverse effects within 1 week of MMF administration. Area under the curve limit of quantification (AUC_0‐LOQh) of MPA ranged from 1.27 to 2.03 hours·μg/mL and from 1.77 to 8.54 hours·μg/mL after the first and last PO dose of 10 mg/kg. The AUC_0‐loqh of MPA ranged from 2.18 to 31 hours·μg/mL after the first dose of 15 mg/kg of MMF. Before the first dose of MMF, the average total number of PBMC ranged from 1.2 to 9.3 million/mL. At the last dose of MMF, the average total number of PBMC ranged from 3 to 5 million/mL.

Conclusion

Mycophenolic acid was detected in all cats. The dose 10 mg/kg given q12h for 1 week was tolerated (n = 3). The efficacy of MMF as an immunosuppressant and long‐term safety in cats of this dosage regimen is unknown.

Successful Treatment of Cutaneous Curvularia geniculata, Nocardia niigatensis, and Viral Papillomatosis in a Dog During the Therapeutic Management of Immune-Mediated Hemolytic Anemia

Opportunistic infections represent a major cause of mortality in immunocompromised patients. Discontinuation or reduction of immunosuppressive medications is recommended with the development of opportunistic infections, which may cause a relapse or worsening of the immune-mediated disease. A 7.5-year-old, spayed female great Dane was diagnosed with immune-mediated hemolytic anemia with initial immunosuppressive therapy consisting of oral prednisone, ciclosporin and mycophenolate mofetil. The patient developed diffuse right forelimb pyogranulomatous fungal dermatitis with deep draining tracts 6 weeks into immunosuppressive treatment with Curvularia geniculata growth. Oral once daily terbinafine and itraconazole were initiated; ciclosporin was immediately discontinued and the mycophenolate mofetil/prednisone doses were reduced. The right forelimb skin lesions resolved after 4 weeks, but the patient presented with a diffuse severe neutrophilic dermatitis on the left forelimb; 16S rRNA sequencing identified Nocardia niigatensis. Cutaneous nocardiosis was treated with oral enrofloxacin and doxycycline; systemic immunosuppressive therapies were continued for immune-mediated hemolytic anemia control. One month later, the left forelimb lesions completely resolved but the patient developed several multifocal, exophytic warts; the clinical features and histopathology were consistent with viral papillomas. Within the following 4 weeks, the patient developed severe diffuse papillomatosis of the left forelimb, which was successfully treated with 2 weeks of every other day topical imiquimod administration. In this case, successful treatment of cutaneous opportunistic bacterial, fungal and viral infection was possible with proper treatment even though the immunosuppressive drug treatments could not be discontinued.

ACVIM consensus statement on the treatment of immune-mediated hemolytic anemia in dogs

Immune‐mediated hemolytic anemia (IMHA) causes severe anemia in dogs and is associated with considerable morbidity and mortality. Treatment with various immunosuppressive and antithrombotic drugs has been described anecdotally and in previous studies, but little consensus exists among veterinarians as to the optimal regimen to employ and maintain after diagnosis of the disease. To address this inconsistency and provide evidence‐based guidelines for treatment of IMHA in dogs, we identified and extracted data from studies published in the veterinary literature. We developed a novel tool for evaluation of evidence quality, using it to assess study design, diagnostic criteria, explanation of treatment regimens, and validity of statistical methods. In combination with our clinical experience and comparable guidelines for humans afflicted with autoimmune hemolytic anemia, we used the conclusions of this process to make a set of clinical recommendations regarding treatment of IMHA in dogs, which we refined subsequently by conducting several iterations of Delphi review. Additionally, we considered emerging treatments for IMHA in dogs and highlighted areas deserving of future research. Comments were solicited from several professional bodies to maximize clinical applicability before the recommendations were submitted for publication. The resulting document is intended to provide clinical guidelines for management of IMHA in dogs. These guidelines should be implemented pragmatically, with consideration of animal, owner, and veterinary factors that may vary among cases.

ACVIM consensus statement on the diagnosis of immune-mediated hemolytic anemia in dogs and cats

Immune-mediated hemolytic anemia (IMHA) is an important cause of morbidity and mortality in dogs. IMHA also occurs in cats, although less commonly. IMHA is considered secondary when it can be attributed to an underlying disease, and as primary (idiopathic) if no cause is found. Eliminating diseases that cause IMHA may attenuate or stop immune-mediated erythrocyte destruction, and adverse consequences of long-term immunosuppressive treatment can be avoided. Infections, cancer, drugs, vaccines, and inflammatory processes may be underlying causes of IMHA. Evidence for these comorbidities has not been systematically evaluated, rendering evidence-based decisions difficult. We identified and extracted data from studies published in the veterinary literature and developed a novel tool for evaluation of evidence quality, using it to assess study design, diagnostic criteria for IMHA, comorbidities, and causality. Succinct evidence summary statements were written, along with screening recommendations. Statements were refined by conducting 3 iterations of Delphi review with panel and task force members. Commentary was solicited from several professional bodies to maximize clinical applicability before the recommendations were submitted. The resulting document is intended to provide clinical guidelines for diagnosis of, and underlying disease screening for, IMHA in dogs and cats. These should be implemented with consideration of animal, owner, and geographical factors.

Pharmacokinetics and pharmacodynamics of mycophenolic acid in healthy cats after twice-daily intravenous infusion of mycophenolate mofetil for three days

OBJECTIVE To evaluate the plasma disposition of mycophenolic acid (MPA) and its derivatives MPA glucuronide and MPA glucoside after twice-daily infusions of mycophenolate mofetil (MMF) in healthy cats for 3 days and to assess the effect of MMF administration on peripheral blood mononuclear cell (PBMC) counts and CD4⁺-to-CD8⁺ ratios. ANIMALS 5 healthy adult cats. PROCEDURES MMF was administered to each cat (10 mg/kg, IV, q 12 h for 3 days). Each dose of MMF was diluted with 5% dextrose in water and then administered over a 2-hour period with a syringe pump. Blood samples were collected for analysis. A chromatographic method was used to quantitate concentrations of MPA and its metabolites. Effects of MMF on PBMC counts and CD4⁺-to-CD8⁺ ratios were assessed by use of flow cytometry. RESULTS All cats biotransformed MMF into MPA. The MPA area under the plasma concentration-time curve from 0 to 14 hours ranged from 14.6 to 37.6 mg·h/L and from 14.4 to 22.3 mg·h/L after the first and last infusion, respectively. Total number of PBMCs was reduced in 4 of 5 cats (mean ± SD reduction, 25.9 ± 15.8% and 26.7 ± 19.3%) at 24 and 48 hours after the end of the first infusion of MMF, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Plasma disposition of MPA after twice-daily IV infusions for 3 days was variable in all cats. There were no remarkable changes in PBMC counts and CD4⁺-to-CD8⁺ ratios.

Mycophenolic acid in patients with immune-mediated inflammatory diseases: From humans to dogs

Mycophenolic acid (MPA), a noncompetitive, selective and reversible inhibitor of inosine 5'-monophosphate dehydrogenase (IMPDH), is an immunosuppressive agent that has a long history in medicine. Mechanistically, the inhibition of IMPDH leads to the selective and eventual arrest of T- and B-lymphocyte proliferation. Mycophenolate mofetil (MMF), the first MPA-based product to receive marketing approval over two decades ago, was originally indicated for the prophylaxis of organ rejection in human transplant patients. Given its broad immunosuppressive properties and ability to selectively inhibit lymphocyte division and effector functions, the clinical utility of MPA was subsequently explored in a host of autoimmune diseases. Human clinical studies have shown MPA to be safe and effective and support its off-label administration for immune-mediated diseases such as lupus, myasthenia gravis and atopic dermatitis. MMF became generically available in the United States in 2008, and its clinical utility is increasingly being explored as a treatment option for dogs with immune-mediated diseases. This review summarizes the available literature for MPA pharmacokinetics and pharmacodynamics, and the current status of MPA as a treatment for client-owned dogs diagnosed with immune-mediated diseases.

Effects of immunosuppressive agents on the hemostatic system in normal dogs

Background

In dogs, the effects of immunosuppressive medications on hemostasis are not well known.

Hypothesis/Objectives

The objective was to determine the effects of immunosuppressive medications on primary and secondary hemostasis. Our hypothesis was that cyclosporine and prednisone would increase markers of hypercoagulability and thromboxane synthesis, while azathioprine, mycophenolate mofetil, and leflunomide would have minimal effects on hemostasis.

Animals

Eight healthy dogs.

Methods

A randomized, cross‐over study used aggregometry, the PFA‐100 platelet function analyzer, viscoelastometry, platelet count, and prothrombin and activated partial thromboplastin times to evaluate hemostasis during the administration of prednisone, azathioprine, cyclosporine, mycophenolate mofetil, and leflunomide for 1 week each at standard oral doses. Urine 11‐dehydro‐thromboxane‐B₂ (11‐dTXB₂) and 6‐keto‐prostaglandin‐F_1α (6‐keto‐PGF_1α) concentrations, normalized to urine creatinine concentration, were measured.

Results

The aggregometry amplitude decreased from 51 ± 21 to 27 ± 14 (P = .002) during leflunomide treatment (ADP activation), but there were no differences in amplitude (P = .240) for any medications when platelets were activated with collagen. For all medications, there were no significant differences in viscoelastometry indices (ACT, P = .666; ClotRate, P = .340; and platelet function, P = .411) and platelet count (P = .552). Compared with pretreatment values, urinary 11‐dTXB₂‐to‐creatinine ratio increased (P = .001) after drug administration (from 3.7 ± 0.6 to 5.6 ± 1.1). Cyclosporine was associated with an increase (P < .001) in the 6‐keto‐PGF_1α‐to‐creatinine ratio (from 10.3 ± 4.6 to 22.1 ± 5.3).

Conclusions and Clinical Importance

Most immunosuppressive drugs do not enhance platelet function or coagulation in healthy dogs, suggesting that these medications might not predispose hypercoagulable dogs to thromboembolism. The results of our study need to be correlated with the clinical outcomes of hypercoagulable dogs.

Indolent, T-cell, large granular lymphocytic leukaemia in a dog presenting with severe neutropenia and an absence of lymphocytosis

In humans, large granular lymphocytic leukaemia (LGLL) is a low-grade, indolent lymphoproliferative disorder of large granular lymphocytes (LGL) associated with autoimmune disorders; including rheumatoid arthritis and single or multiple cytopenias; particularly neutropenia. Therapy largely centres around immunosuppression which aims to resolve the immune-mediated secondary pathology, often without eradicating the neoplastic clone. The most effective agents appear to be cyclophosphamide, cyclosporine and methotrexate. This case report describes the presentation, diagnostics, therapeutic approach and outcome of a 6 year-old Golden Retriever presenting with severe neutropenia. Chlorambucil, prednisolone and cyclosporine failed to improve the neutropenia but subsequent cyclophosphamide resulted in a sustained albeit temporary improvement in neutrophil count and the ability to withdraw prophylactic antibacterials. This case closely mirrors the diagnostics and therapeutic response in human LGLL.

Safety of oral and intravenous mycophenolate mofetil in healthy cats

Objectives The aim of this study was to evaluate the safety and clinical effects of intravenous (IV) and oral mycophenolate mofetil (MMF) in healthy cats. Methods A total of 24 healthy adult cats weighing >3.5 kg were either given IV MMF (over a 2 h infusion) or oral MMF. The dosages used were as follows: 5 mg/kg IV once (n = 2), 10 mg/kg q12h IV for 1 day (n = 1), 20 mg/kg q12h IV for 1 day (n = 6) and 10 mg/kg q12h IV for 3 days (n = 5). Blood was collected from each cat at intervals of up to 12 h from the last dose for analysis purposes. Oral MMF was given at 10 mg/kg q12h for 7 days (n = 3), 15 mg/kg q12h for 7 days (n = 3) and 15 mg/kg q8h for 7 days (n = 4). Results Side effects to MMF were minimal. There was no anorexia or vomiting noted in any of the cats during or after IV medication administration. Only 4/14 cats had diarrhea from 12-48 h after IV administration. There was hyporexia in 1/10 cats given oral MMF and no vomiting noted. In 5/10 cats given oral MMF, there was diarrhea between days 2 and 7 of the study. Conclusions and relevance Cats tolerate MMF at an IV dose of 10 mg/kg q12h for 3 days and an oral dose ⩽15 mg/kg q12h for up to 7 days. There seems to be a dose-dependent incidence of gastrointestinal side effects. MMF may be a useful alternative immunosuppressant to be considered for use in some cats.

Pharmacokinetics of Mycophenolic Acid after Intravenous Administration of Mycophenolate Mofetil to Healthy Cats

Background

Mycophenolate mofetil (MMF), the prodrug of mycophenolic acid (MPA), is becoming increasingly popular as an alternative immunosuppressant in feline medicine. Pharmacokinetic information is not available for cats.

Objective

The purpose of this study was to determine whether MMF is biotransformed into the active metabolite MPA and to evaluate the disposition of MPA after a 2‐hour constant rate intravenous (IV) infusion of MMF in healthy cats.

Animals

Healthy cats (n = 6).

Methods

This was a prospective pilot study. All cats were administered MMF at 20 mg/kg every 12 hours over a 2‐hour constant rate infusion for 1 day. The concentrations of MPA and its derivatives in blood were determined using a validated UHPLC–UV method.

Results

All cats biotransformed MMF into MPA. The mean AUC_0‐14 h ranged from 6 to 50 h*mg/L after IV dosing of MMF. Transient large bowel diarrhea was recorded in 2 of 6 cats after medication administration.

Conclusion and Clinical Importance

The disposition of MPA in plasma was highly variable, which could result in high interindividual variability in the safety and efficacy of treatment with MMF in cats.

Anti-thymocyte serum as part of an immunosuppressive regimen in treating haematological immune-mediated diseases in dogs

OBJECTIVES

To report the outcomes associated with the use of rabbit anti-dog thymocyte serum in dogs with haematological immune-mediated diseases.

METHODS

Medical records from 2000 to 2016 of patients diagnosed with immune-mediated haemolytic anaemia, immune-mediated thrombocytopenia, pancytopenia and myelofibrosis were reviewed. All dogs had a severe or refractory disease and received rabbit anti-dog thymocyte serum. Lymphocyte counts were used to monitor the immediate anti-thymocyte effect of therapy; long-term patient outcome was recorded.

RESULTS

A total of 10 dogs were included. All dogs except one had a notable decrease in their lymphocyte count after rabbit anti-dog thymocyte serum; four of nine had a decrease to less than 10% of the initial lymphocyte count and one dog reached 10·8%. All dogs were discharged from the hospital following their treatment. The dog with no alteration of lymphocyte count following therapy with rabbit anti-dog thymocyte serum had refractory immune mediated haemolytic anemia and was euthanised within two weeks. All other cases achieved clinical remission with immunosuppressive therapy eventually being tapered (3 of 10) or discontinued (6 of 10).

CLINICAL SIGNIFICANCE

Rabbit anti-dog thymocyte serum therapy might be of interest as an adjunctive therapy in refractory immune-mediated diseases and suppressed lymphocyte counts in most dogs.

Canine autoimmune hemolytic anemia: management challenges

Immune-mediated hemolytic anemia is one of the most common manifestations of canine immune-mediated disease, yet treatment regimens remain nonstandardized and, in some cases, controversial. The main reason for this, as for most diseases in veterinary medicine, is the lack of large-scale placebo-controlled trials so that the efficacy of one treatment over another can be established. Most of the evidence used for treatment comes from retrospective studies and from personal preference and experience, and because of this, treatment regimens tend to vary among institutions and individual clinicians. Management of immune-mediated hemolytic anemia includes immunosuppression, thromboprophylaxis, and supportive care measures to help prevent and treat concurrent conditions.

Comparative metabolism of mycophenolic acid by glucuronic acid and glucose conjugation in human, dog, and cat liver microsomes

Use of the immunosuppressant mycophenolic acid (MPA) in cats is limited because MPA elimination depends on glucuronidation, which is deficient in cats. We evaluated formation of major (phenol glucuronide) and minor (acyl glucuronide, phenol glucoside, and acyl glucoside) MPA metabolites using liver microsomes from 16 cats, 26 dogs, and 48 humans. All MPA metabolites were formed by human liver microsomes, while dog and cat liver microsomes formed both MPA glucuronides, but only one MPA glucoside (phenol glucoside). Intrinsic clearance (CLint) of MPA for phenol glucuronidation by cat liver microsomes was only 15-17% that of dog and human liver microsomes. However, CLint for acyl glucuronide and phenol glucoside formation in cat liver microsomes was similar to or greater than that for dog and human liver microsomes. While total MPA conjugation CLint was generally similar for cat liver microsomes compared with dog and human liver microsomes, relative contributions of each pathway varied between species with phenol glucuronidation predominating in dog and human liver microsomes and phenol glucosidation predominating in cat liver microsomes. MPA conjugation variation between cat liver microsomes was threefold for total conjugation and for phenol glucosidation, sixfold for phenol glucuronidation, and 11-fold for acyl glucuronidation. Our results indicate that total MPA conjugation is quantitatively similar between liver microsomes from cats, dogs, and humans despite large differences in the conjugation pathways that are utilized by these species.

In Vitro Influence of Mycophenolic Acid on Selected Parameters of Stimulated Peripheral Canine Lymphocytes

Mycophenolic acid (MPA) is an active metabolite of mycophenolate mofetil, a new immunosuppressive drug effective in the treatment of canine autoimmune diseases. The impact of MPA on immunity is ambiguous and its influence on the canine immune system is unknown. The aim of the study was to determine markers of changes in stimulated peripheral canine lymphocytes after treatment with MPA in vitro. Twenty nine healthy dogs were studied. Phenotypic and functional analysis of lymphocytes was performed on peripheral blood mononuclear cells cultured with mitogens and different MPA concentrations– 1 μM (10⁻³ mol/m³), 10 μM or 100 μM. Apoptotic cells were detected by Annexin V and 7-aminoactinomycin D (7-AAD). The expression of antigens (CD3, CD4, CD8, CD21, CD25, forkhead box P3 [FoxP3] and proliferating cell nuclear antigen [PCNA]) was assessed with monoclonal antibodies. The proliferation indices were analyzed in carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled cells. All analyses were performed using flow cytometry. The influence of MPA on apoptosis was dependent on the mechanism of cell activation and MPA concentration. MPA caused a decrease in the expression of lymphocyte surface antigens, CD3, CD8 and CD25. Its impact on the expression of CD4 and CD21 was negligible. Its negative influence on the expression of FoxP3 was dependent on cell stimulation. MPA inhibited lymphocyte proliferation. In conclusion, MPA inhibited the activity of stimulated canine lymphocytes by blocking lymphocyte activation and proliferation. The influence of MPA on the development of immune tolerance–expansion of Treg cells and lymphocyte apoptosis–was ambiguous and was dependent on the mechanism of cellular activation. The concentration that MPA reaches in the blood may lead to inhibition of the functions of the canine immune system. The applied panel of markers can be used for evaluation of the effects of immunosuppressive compounds in the dog.

Evaluation of the safety and tolerability of rivaroxaban in dogs with presumed primary immune-mediated hemolytic anemia

OBJECTIVE

To evaluate the safety and tolerability of rivaroxaban (RIV), an oral direct factor Xa inhibitory drug, in dogs with presumed primary immune-mediated hemolytic anemia (pIMHA).

DESIGN

Prospective, multicenter, positive-controlled, unblinded clinical trial. Client-owned dogs were enrolled between October 2012 and March 2014.

SETTING

Private referral centers.

ANIMALS

Twenty-four client-owned dogs with pIMHA. Enrolled dogs were randomized in 2 treatment groups to receive by mouth RIV or clopidogrel (CL) and low-dose aspirin (LDA). All dogs were monitored for 90 days from the enrollment in the study.

INTERVENTIONS

Enrolled dogs were given a standardized immunosuppressive protocol and RIV or CL and LDA.

MEASUREMENTS AND MAIN RESULTS

There was no identifiable adverse drug reaction, evidence of hemorrhage, significant prolongation of prothrombin time or activated partial thromboplastin time, or increase in transfusion requirements associated with RIV therapy compared to CL and LDA in dogs with pIMHA. There was no significant difference between treatment groups with respect to thrombotic events, survival rates to discharge, at 1 month and 3 months from diagnosis.

CONCLUSIONS

This study suggests that RIV at a median dose of 0.89 mg/kg by mouth once daily was safe and well tolerated in a small group of dogs with presumed pIMHA able to tolerate oral medications and treated with a standardized immunosuppressive treatment protocol. Conclusions regarding the relative efficacy of RIV as compared to CL and LDA cannot be made due to the small size of the treatment groups and because pharmacodynamic effects were not assessed.

Treatment of canine meningoencephalomyelitis of unknown aetiology with mycophenolate mofetil and corticosteroids: 25 cases (2007-2012)

The use of mycophenolate mofetil (MMF) for a variety of immune‐mediated diseases in veterinary medicine has been described. However, there is only a small number of cases documenting its use in dogs with meningoencephalomyelitis of unknown aetiology (MUE). We hypothesized that the use of MMF and corticosteroids in dogs with MUE results in comparable survival data to other published treatment protocols and is associated with limited adverse effects. A retrospective study of medical case records of dogs clinically diagnosed with MUE recorded signalment, neuroanatomic localization, magnetic resonance imaging findings, cerebrospinal fluid analysis results, medications administered, follow‐up neurologic examinations, survival and adverse events. Variables were compared between dogs which were treated with MMF within 30 days of diagnosis (immediate group) vs. dogs in which MMF therapy was started >30 days after diagnosis (delayed group). Twenty‐five cases of MUE were identified. The overall median survival time from diagnosis was 731 days (range 43–1672 days). After 1 month of MMF treatment, 92% of dogs showed improvement on a neurological examination. There was no significant effect of any recorded parameter on survival, including delayed vs. immediate initiation of MMF treatment. Dogs with delayed treatment had significantly lower clinical remission rates than dogs with immediate treatment at 6 months after starting MMF. Adverse events were identified in two cases (8%) and were characterized by mild gastrointestinal signs (vomiting and decreased appetite). Administration of MMF appears safe in dogs with MUE. The use of MMF results in comparable survival times to alternate immunosuppressive protocols.

Procoagulant microparticles in dogs with immune-mediated hemolytic anemia

Background

Studies of some human prothrombotic diseases suggest that phosphatidylserine‐positive (PS+) and tissue factor‐positive (TF+) microparticles (MPs) might play a role in the pathogenesis of thrombosis or serve as biomarkers of thrombotic risk.

Hypothesis/Objectives

To determine if circulating levels of PS+MP and procoagulant activity (PCA) associated with PS+MPs and TF+ MPs are increased in dogs with IMHA.

Animals

Fifteen dogs with primary or secondary IMHA and 17 clinically healthy dogs.

Methods

Prospective case‐controlled observational study. Circulating PS+MPs were measured by flow cytometry. PCA associated with PS+MPs and TF+MPs was measured by thrombin and Factor Xa generating assays, respectively.

Results

Circulating numbers of PS+MPs were not significantly higher in dogs with IMHA [control median 251,000/μL (36,992–1,141,250/μL); IMHA median 361,990/μL (21,766–47,650,600/μL) P = .30]. However, PS+MP PCA [control median 2.2 (0.0–16.8) nM PS eq; IMHA median 8.596, (0–49.33 nM PS eq) P = .01] and TF+MP PCA [control median 0.0, (0.0–0.0 pg/mL); IMHA median 0.0; (0–22.34 pg/mL], P = .04) were increased. Intravascular hemolysis, which we showed might increase PS+ and TF+MP PCA, was evident in 3 of 5 dogs with PS+MP PCA and 2 of 4 dogs with TF+MP PCA higher than controls. Underlying disease in addition to IMHA was detected in 1 of 5 dogs with PS+PCA and 3 of 4 dogs with TF+MP PCA higher than controls.

Conclusions and Clinical Importance

TF+ and PS+MP PCA is increased in some dogs with IMHA. Further studies that determine if measuring TF+ and PS+ MP PCA can help identify dogs at risk for thrombosis are warranted.