IMMUNE-MEDIATED
HEMOLYTIC ANEMIA
(IMHA)
By Guardian Angel Joanne & Angel Asia
Immune Mediated
Hemolytic Anemia (IMHA) and Autoimmune Hemolytic Anemia
(AIHA) are basically the same so don't let the two different names
confuse you.
This article on IMHA refers to dogs in general NOT just dogs with autoimmune
thyroiditis. Any dog can be diagnosed either with IMHA or AIHA.
I know that it is difficult to wade through these reports to try and find
the information you need. I think it is
important to have the whole report (included below)
but I will snippet the part I believe is important to pay
attention to. I will also put this sentence in italics in the body of
the report (the 2nd paragraph) so that you can find it
easier. The references for your vet are at the end of
the article...
While many cases (of IMHA) may be classified as idiopathic, a recent
stress event such as vaccination, drug, chemical or toxic exposure,
surgery, hormonal change, infection, or injury within
the previous 30-45 days may be identified as a
potential trigger.
My pup, Asia, collapsed and
was diagnosed with autoimmune hemolytic anemia exactly
30 days after she was accidentally given a distemper/parvo booster.
She died two weeks later. I would like to know her death was not in vain
and that you will consider titers testing
rather than annual vaccination boosters....
From the Antech website:
http://antechdiagnostics.com/
"Antech Diagnostics is a nationwide network of 18 integrated veterinary
diagnostic laboratories dedicated to providing clients the finest in
laboratory medicine. Clients can access resources
such as the Services Directory, Consultant
Guide, current and past issues of Antech News, and
Quality Assurance information. Monthly web specials are also offered for
clients who access the website."
Antech Diagnostics Immune-Mediated Hemolytic Anemia report July 2001
http://www.antechdiagnostics.com/clients/antechnews/2001/7-01.htm
Immune-mediated hematologic disease including hemolytic anemia (IMHA) and/or
thrombocytopenia is being reported with increasing frequency in animals
and humans. In dogs and
occasionally in cats, this disorder can be associated
with bone marrow failure (nonregenerative anemia, erythroid dysgenesis, red
cell aplasia). Affected animals have one or more of the following signs:
lethargy, anorexia, pale mucous membranes, weakness, exercise
intolerance, tachycardia, tachypnea, icterus,
hemoglobinuria and fever. Prognosis is guarded to poor
with reported mortality rates between 28-70%. Laboratory
abnormalities may include: red cell
auto-agglutination, positive Coombs’ test,
spherocytosis, thrombocytopenia, and neutrophilia. Anemia may be
regenerative or nonregenerative depending on the duration of illness and
immunological targeting of red cell precursors in the bone marrow. Some
dogs may also have other autoimmune diseases.
While many cases may be classified as idiopathic, a recent stress event such
as vaccination, drug, chemical or toxic exposure, surgery, hormonal
change, infection, or injury within the previous 30-45
days may be identified as a potential trigger. Many
breeds are reported to have an increased risk for IMHA,
and mixed breed dogs can also be affected.
Four recent retrospective studies have addressed the clinical and laboratory
findings and compared treatment outcomes of dogs with IMHA. In one study
of 70 cases, Cocker Spaniels, English Springer
Spaniels, Poodles, Miniature Schnauzers, and Collies
were at increased risk. Only 3 dogs had been
vaccinated within 2 weeks of the diagnosis. Regenerative anemia was present
in 83% and 79% had spherocytosis. Only 37% of the dogs had positive
Coombs’ test. Thrombocytopenia was also found in 29
dogs. Elevated serum bilirubin concentrations, present
in 68% of cases, was significantly associated with
decreased survival. A significant difference in survival was found between
treatment groups (see Table).
The overall mortality was 70%. While 29 dogs died or were euthanized during
hospitalization, 41 were discharged but 15 died, most within 3 months of
discharge. Dogs with IMHA were four times more likely to die than dogs in
the general hospital population.
The second study involved 60 cases. Cocker Spaniels had a 3.3 times
increased relative risk for IMHA. Unlike an
earlier study, no seasonal incidence, or correlation
between vaccination and onset of disease or survival times was
found. Positive Coombs’ test and autoagglutination were seen in 89% of
cases, and 75% had spherocytosis. The anemia
was regenerative in 42% and
nonregenerative in 58%. Increased bilirubin concentrations were present in
80% of cases, but hyperbilirubinemia was not associated with higher
mortality. The median survival time was only 21 days. Dogs receiving
prednisone, cyclophosphamide, and azathioprine had a median survival time
of 370 days as compared to only 9 days for those given
only prednisone and cyclophosphamide. Of the dogs
given compatible transfusions, no adverse effects were
recorded and the median survival time was better (21 days)
versus 2 days for dogs that were not transfused. Overall mortality was
52%. Thirty-three dogs were discharged and followed
for at least 2 years; 8 dogs relapsed and in 7 of
these, relapse occurred within 21 days of discharge.
The third study included 88 dogs. Twenty-six dogs received only prednisone.
Of these, 15 (58%) survived to be discharged, and the mortality rate was
30%. The relative risk of death for dogs
treated with prednisone and azathioprine (n=27),
prednisone and danazol (n=16), prednisone and cyclosporine (n=24) or
prednisone and intravenous gamma globulin (n=7) was not different from
dogs treated only with prednisone. With
cyclophos-phamide, however, there was a significant
increased risk of mortality. Although dogs with
autoagglutination were twice as likely to be treated
with cyclophosphamide, there was no significant
relationship between autoagglutination and mortality. The mean
PCV of dogs that were treated with cyclophosphamide was not significantly
different from dogs not receiving this drug. The 3 dogs receiving bovine
hemoglobin solution did not survive. Overall mortality rate in this study
was 50%, but dogs were followed only until discharge.
The last study involved 43 dogs with severe idiopathic nonregenerative
anemia. Labrador Retrievers were overrepresented here. While 54% of cases
had spherocytosis and 57% had positive Coombs
tests, only 5% had autoagglutination. Seven of 31 dogs
tested (23%) had positive antinuclear antibody titers.
Leukocyte counts were normal, but 22% of the dogs had some
degree of thrombocytopenia. All dogs had bone marrow biopsies. Bone
marrow aspirates were
difficult to obtain in 27 dogs, and core marrow biopsies were
performed in 16 of them. Fifty-five percent of dogs had erythroid
hyperplasia, 14% had normal erythrogenesis and 26% had erythroid
hypoplasia, 37% had erythroid maturation arrest, and 2
dogs had pure red cell aplasia with no red blood cell
precursors found. All 16 core biopsies revealed
myelofibrosis. Iron stores were moderate in 23% and large in 72% of the
dogs. Treatment outcomes varied with responses
seen in 1-10 weeks (see Table).
Follow-up bone marrow biopsy on 2 dogs showed resolution of myelofibrosis.
Overall mortality was 28%.
Conclusion: Prognosis for dogs with IMHA is guarded to poor. The various
combination drug protocols may not work better than corticosteroids
alone. Use of cyclophosphamide to treat dogs with the
regenerative form of IMHA may be associated with
increased mortality. Dogs with the non-regenerative form
of IMHA do not have a worse prognosis than dogs with the classic
regenerative form. Myelofibrosis can occur
secondary to immune-mediated destruction of red
cell precursors and may respond to immunosuppressive therapy.
References: Dodds, Can Vet J 37 (3): 133, 1996; Reimer et al, JAAHA 35:
384-391, 1999; Burgess et al, JVIM 14: 456-462, 2000; Grundy and Barton,
JAVMA 218: 543-546, 2001; Stokol et al, JAVMA 216: 1429-1436, 2001.