Successful treatment of immune-mediated hemolytic anemia in a pregnant dog: a case report

Abstract

A 2.5-year-old female Dachshund was diagnosed and treated for immune-mediated hemolytic anemia (IMHA) during late-term pregnancy. The dog had been treated for a urinary infection approximately 1 week prior to presentation with amoxicillin-clavulanic acid and became increasingly lethargic at home. When the dog was presented to a university teaching hospital, the dog was significantly anemic and later diagnosed with IMHA, either secondary to pregnancy or potentially associated with previous antibiotic treatment. The dog was hospitalized for 5 days and received multiple blood transfusions, immunosuppressive steroids, and progesterone to maintain pregnancy. One week after hospital discharge, the dog successfully gave birth to four puppies at home. One week postpartum, the dog’s anemia had begun to resolve, and the dog was weaned off steroids after 6 weeks. This case report is important for practitioners who may also diagnose and treat a pregnant dog with an immune-mediated disease, and it represents a successful outcome for both the dam and litter.

Introduction

Immune-mediated hemolytic anemia (IMHA) is one of the most common hemolytic disorders affecting dogs and is associated with high rates of morbidity and mortality (1). In this disease, the body produces antibodies against red blood cells, causing either direct destruction or phagocytosis of red blood cells, resulting in anemia. Mortality rate varies but is commonly reported at >40%, with death most commonly due to severe anemia, thromboembolism, or failure to respond to treatment (2). IMHA is categorized as either primary, with no known trigger or immunogenic stimulus, or secondary, in which an underlying disease, trigger, or risk factor is responsible for antibody production that leads to the destruction of red blood cells (3). Diagnosis per the latest veterinary guidelines requires two signs of immune-mediated red blood cell destruction, one sign of hemolysis. Diagnosis supportive of IMHA requires at least one sign of destruction and one sign of hemolysis. Common risk factors include recent vaccination and drug administration, while triggers may include tickborne diseases, neoplasia, and estrus (3). Treatment requires removal of the inciting cause if secondary, and immunosuppressive therapy by way of glucocorticoids, blood transfusions, and other second-line immunosuppression treatments which carry their own adverse effects (4).

While pregnancy associated with IMHA has been reported in both human and veterinary literature, successful treatment using glucocorticoids and blood transfusions has only been reported in humans (5–7). There is limited evidence on medical management of IMHA during pregnancy, as the few cases previously reported resulted in signs resolving with termination of gestation (8, 9). This case represents an alternative strategy to terminating pregnancy and describes the first report of IMHA in a pregnant dog managed with immunosuppressive therapy and blood transfusions prior to natural whelping of healthy puppies, followed by the resolution of IMHA.

Case summary

A 2.5-year-old female pregnant Dachshund was referred to a university teaching hospital for severe anemia diagnosed by the primary care veterinarian. The dog was reportedly lethargic for the previous 2 to 3 days. The dog had been mated by live cover 48 days prior to presentation and had one previous uneventful pregnancy, which yielded a litter of four puppies a year prior. The dog had been diagnosed with a lower urinary tract infection and a single cystolith approximately 1 month prior to presentation and had been placed on amoxicillin-clavulanic acid (Zoetis Parsippany, NJ) for 1 week (medication discontinued approximately 3 weeks prior to presentation). Additionally, the same series of radiographs obtained by the primary care veterinarian showed four fetal skeletons (Figure 1). The dog had no history of tick or flea exposure or travel outside of Florida. At the primary care veterinarian, an in-house hematology revealed a severe normocytic, normochromic anemia (hematocrit 9.9%; reference interval [RI]: 37–55), leukocytosis (29 K/μL; RI: 6–17 K/μL), and hyperbilirubinemia (1.3 mg/dL; RI: 0–0.9 mg/dL).

Figure 1.

Left lateral and ventrodorsal abdominal radiographs from a 2.5 year old pregnant dog transferred with suspected IMHA; red arrows indicating multiple feti and green arrows representing a single cystolith.

On clinical examination at the university hospital, the dog was tachycardic (168 beats per minute), with white mucous membranes, and had a distended, soft abdomen on palpation. The remainder of the exam was within normal limits. A PCV/TS, bedside blood smear analysis, and blood type were performed, which showed a severe anemia (PCV 10%; RI: 40–55%), normal total solids (6.0 g/dL; RI: 6–7.5 g/dL), marked hypochromia, and a DEA 1.1 positive blood type. A point-of-care ultrasound revealed multiple fetal heart rates between 200 and 220 bpm. Serology for Borrelia burgdorferi, Ehrlichia, and Anaplasma and antigen detection for Dirofilaria immitis were all negative. Fecal analysis by floatation confirmed no parasite ova present. An in-house saline agglutination test was performed by mixing a drop of blood with saline (1:10 dilution), which was negative for both macroscopic and microscopic agglutination. A free catch urinalysis revealed many cocci and too numerous to count white blood cells, and 3 + bilirubin. A full hematology panel was submitted for clinical pathologist review, which revealed a strongly regenerative anemia (absolute reticulocyte count 291.9 K/μL; RI: 12.9–86 K/μL and HCT 9.6%; RI: 40–56%). On clinical pathologist blood smear review, both anisocytosis and polychromasia, and rare spherocytes (0–1/100x field) were noted. A diagnosis of IMHA was suspected and made based on a strongly regenerative anemia, presence of spherocytosis, bilirubinuria, and hyperbilirubinemia (or evidence of hemolysis). Once admitted to the intensive care unit, the dog received the following therapies: a packed red blood cell transfusion (27 mL/kg) intravenously (IV) over 4 h, ondansetron (Pfizer, Kalamazoo, MI; 0.5 mg/kg) IV every 8 h, maropitant (Zoetis, Parsippany, NJ; 1 mg/kg) IV every 24 h, an iron dextran (MWI, Boise, ID; 20 mg/kg) intramuscular injection, and lactated Ringer’s solution (Dechra, Northwich, UK) IV at a maintenance rate. Post-transfusion, the dog’s PCV/TS increased to 20% with a total solid of 5.6 g/dL, and her vitals improved. On day 3 of hospitalization, the dog became more lethargic, tachycardic, and pale. A repeat PCV was performed, yielding 12%; an additional packed red blood cell transfusion (24 mL/kg) was administered IV. At this time, the dog was started on an immunosuppressive dose of dexamethasone (MWI, Boise, ID; 0.3 mg/kg) IV and 0.08 mg/kg of altrenogest (Aurora Pharmaceuticals, Northfield, MN; progesterone) to suppress estrus to maintain her pregnancy while beginning steroid treatment, which is known to induce labor/parturition. While in the hospital, fetal heart rates were monitored every 12 h, and progesterone was monitored daily. Over the course of days 4 and 5, the dog improved clinically, and additional blood transfusions were not indicated, and anorexia resolved. On day 5, the dog was discharged on amoxicillin (Zoetis, Parsippany NJ) 20 mg/kg by mouth every 12 h to treat for the lower urinary tract infection, prednisone (Lloyds pharmacy, Coventry, England) 1 mg/kg by mouth every 12 h for continued immunosuppression, altrenogest 0.08 mg/kg by mouth every 24 h through day 60 post-mating to maintain pregnancy, and capromorelin (Elanco, Indianapolis, IN) 3 mg/kg by mouth every 24 h as needed to stimulate appetite. Three weeks later, the dog whelped four healthy puppies. The dog and puppies were evaluated 1-week post-whelping. No gross anatomical congenital abnormalities were present in the neonates, and the dam’s postpartum exam was normal. At that time, the dog’s PCV was 33% (Table 1), and a steroid taper was initiated by reducing the prednisone dose by 25%. The dog was tapered off steroids completely by 6-week postpartum. The dog was followed for 18-month post-IMHA diagnosis, during which she was spayed, underwent a cystotomy to remove the cystolith, and had no evidence of relapse of IMHA. The puppies were reportedly healthy when they were adopted by new owners.

Table 1.

Hematocrit trends during and after hospitalization.

Packed cell volume	Day 1 (9/7) Pre transfusion	Day 1 (9/7) Post transfusion	Day 2 (9/8)	Day 3 (9/9) Pre transfusion	Day 3 (9/9) Post transfusion	Day 4 (9/10)	Day 5 (9/11)	Day 10 (9/16)	Day 25 (10/2)
PCV (40–52%)	10	20	20	20	12	27	29	30	33

Discussion

This case reports not only a diagnosis of IMHA in a pregnant dog, but also the first report of successful management of IMHA in a pregnant dog without complications in the dam or full-term puppies. Pregnancy-induced immune-mediated hemolytic anemia has recently been documented in a dog and a cat (8, 9). However, in these cases, the animals either had surgery to remove the litter (8), or gave birth prior to medical management of disease (9). An additional case report describes a French Bulldog diagnosed with pregnancy-associated immune-mediated thrombocytopenia diagnosed on day 59 of gestation. In this case, the dog was medically managed with blood transfusions, glucocorticoids, vincristine, and mycophenolate for 7 days during which the dog passed three dead fetuses, then underwent a cesarean section on day 8, where one remaining stillbirth puppy was delivered (10). Of these reports, this is the first to document the treatment of preterm without complications for the dam or puppies. In humans, anemia and thrombocytopenia are two of the most common bleeding complications associated with pregnancy, with estimates of 3 out of 100,000 pregnancies per year of pregnancy-induced autoimmune hemolytic anemia (termed AIHA) (5, 11). IMHA in this case was diagnosed based on the presence of regenerative anemia, spherocytosis, and hyperbilirubinemia, and was classified as secondary either to previous antibiotic usage (amoxicillin/clavulanic acid) or to pregnancy. Serological testing for tick-borne diseases was negative, and other non-immune-mediated causes were excluded due to the absence of metallic foreign material in imaging studies and lack of toxin ingestion from the dog’s history.

Pregnancy-induced hemolytic anemia is an uncommon and poorly understood entity in the human literature, occurring within the second or third trimester and resolving within the postpartum period (11–13). Alloimmunization, the process by which maternal antibodies attack fetal antigens, has been well documented and understood in human medicine and is similar to neonatal isoerythrolysis documented in queens and their kittens (11, 14, 15). In this disease, the mother suffers minimal to no complications while the fetus may experience significant hemolysis, low birth weight, or commonly death in kittens post partum (14). The cause is incompatibility of the fetuses’ blood types (whether due to red blood cell antigens or the Rhesus factor in women). Both processes, however, differ from autoimmune hemolytic anemia, whereby both mothers and offspring experience significant complications due to hemolysis, with the etiology still poorly understood in human medicine (16).

For human patients requiring medical management prior to delivery for autoimmune hemolytic anemia, corticosteroids and red blood cell transfusions are the mainstay of treatment, with healthy offspring born to these patients having been reported (5, 7, 11). Given it is a rare diagnosis with relatively scarce reporting of the diagnosis, a consensus on standardized treatment for pregnancy-induced autoimmune hemolytic anemia in women has yet to be reached (17).

Corticosteroids are used to suppress the hypothalamic pituitary gonadal axis, and among many of their functions, decrease the release of progesterone, an important hormone in the estrus cycle. Progesterone suppresses the release of LH and FSH from the pituitary gland, which normally stimulates follicular development and ovulation during pregnancy. There is a tight equilibrium of glucocorticoids and progesterone to remain synergistic and maintain the pregnancy, and disequilibrium between these hormones has led to fetal distress, premature birth, and preterm death (18). Suppression of progesterone by means of high doses of corticosteroid treatment may lead to disequilibrium of hormones during pregnancy, resulting in the aforementioned complications. In women, many studies have evaluated the use of progesterone to maintain pregnancy in those who are at high risk for miscarriage, as well as those undergoing in vitro fertilization treatment (19, 20). In our case, we implemented progesterone to offset the unwanted consequences of high-dose steroid administration and early termination of pregnancy.

Blood transfusions, specifically packed red cell infusions, are recommended in the treatment of IMHA in patients (both human and canine/feline) who develop clinical hemolysis while receiving immunosuppressive therapy (4). While blood transfusions occur during pregnancy in women, they are more common peripartum due to hemorrhage during childbirth, and currently, there is minimal reporting on transfusion outcomes in pregnant women who receive transfusions prepartum (21). To our knowledge, we report the first pregnant canine receiving a blood transfusion due to IMHA during pregnancy without complication.

Thromboprophylaxis has become an increasing topic of discussion in human medicine as it is well established that pregnancy alone causes hypercoagulability, and venous thromboembolisms are one of the leading causes of morbidity and mortality in pregnant women (22, 23). Currently, there is no consensus for treatment in pregnant women. Thromboprophylaxis in human medicine is reserved for patients who are clinically at risk or have been previously diagnosed with thromboembolic disorders. In our case, we elected to withhold thromboprophylaxis despite current veterinary recommendations to initiate anticoagulant therapy at the time of IMHA diagnosis (4). Much like human medicine, we weighed the risks and benefits concerning peripartum bleeding risks and elected to withhold anticoagulant treatment in an effort to minimize bleeding risks in proximity to her due date.

There are a few limitations to this case report. First was the inability to distinguish if the dam’s hemolytic anemia was secondary to medication (previously prescribed antibiotic), infection (UTI), or her pregnancy. While we initially considered a drug-induced cause of her anemia, this was disregarded given how quickly the patient resolved post-partum and that she was maintained on a similar antibiotic (but without clavulanic acid), a known postpartum to treat her urinary tract infection and there was no reported relapse of anemia. We also did not perform a thorough diagnostic investigation into the possibility of neoplasia, as it was much lower on our differential list, but still possible. In addition, the puppies were followed for only 8 weeks before they were rehomed. While no gross anatomical abnormalities were present, it is unknown if there were any long-term effects on the neonates. We suspect this is unlikely, as congenital issues typically develop early in pregnancy, and the dam was treated for IMHA in late pregnancy.

Conclusion

Pregnancy-associated immune-mediated hemolytic anemia occurs rarely in both human and veterinary medicine. Standardized treatment with blood transfusions and glucocorticoids should be considered preterm if suspected, as well as additional hormone therapy to maintain pregnancy until term. Hemolysis and anemia in pregnant dogs should prompt an investigation into IMHA. Traditional treatment for IMHA is possible with concurrent pregnancy and has been demonstrated to be successful prior to delivery of healthy puppies without compromising the dam’s health.

Funding Statement

The author(s) declared that financial support was not received for this work and/or its publication.

Data availability statement

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author.

Ethics statement

The requirement of ethical approval was waived by University of Florida Institutional Animal Care and Use Committee for the studies involving animals because data was collected from animal records were treated within the hospital. The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent was obtained from the owners for the publication of this case report.

Author contributions

DC: Investigation, Writing – original draft, Writing – review & editing. CC: Investigation, Writing – review & editing. AA-D: Funding acquisition, Supervision, Writing – review & editing, Investigation.

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The author(s) declared that Generative AI was not used in the creation of this manuscript.

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