Immune-mediated haemolytic anaemia and thrombocytopenia in 25 adult equids: 1997-2016.
Authors: Easton-Jones Charlotte A, Estell Krista E, Magdesian K Gary
Journal: Equine veterinary journal
Summary
# Immune-mediated haemolytic anaemia and thrombocytopenia in equids: clinical outcomes and prognostic indicators Immune-mediated haemolytic anaemia (IMHA) and thrombocytopenia (IMTP) represent poorly characterised conditions in horses, with limited evidence regarding their underlying causes, clinical trajectory and survival rates. This retrospective case analysis reviewed 25 equids diagnosed with IMHA, IMTP or concurrent disease between 1997 and 2016, comparing clinicopathological findings and outcomes with control animals presenting with non-immune disease. A striking finding emerged: neoplasia was identified in 28% of IMHA/IMTP cases versus only 8% of controls (P = .04), suggesting malignancy is a significant underlying driver of secondary immune disease in equids. Critically, prognosis varied substantially by disease classification—horses with primary IMHA/IMTP had an 89% survival rate to discharge (8/9 cases), whilst those with secondary disease achieved only 44% survival (7/16 cases), with elevated blood urea nitrogen (BUN) emerging as a powerful prognostic indicator (OR = 19.5 for mortality when BUN elevated; P = .009). Clinicians should pursue aggressive diagnostic screening for occult neoplasia in horses presenting with immune-mediated anaemia or thrombocytopenia, recognise the substantially poorer outlook for secondary cases, and consider elevated renal parameters as a critical warning sign; conversely, primary cases warrant treatment optimism and intensive supportive care.
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Practical Takeaways
- •Primary IMHA/IMTP cases warrant aggressive treatment as they have reasonable prognosis; secondary cases associated with neoplasia carry poor prognosis and may warrant palliative approach
- •Measure BUN on presentation as a prognostic indicator—elevated levels suggest higher mortality risk and should influence clinical decision-making
- •Screen for underlying neoplasia in horses presenting with immune-mediated haemolytic anaemia or thrombocytopenia, as cancer is significantly overrepresented in this population
Key Findings
- •Neoplasia was significantly more common in study animals (28%) versus controls (8%, P=0.04)
- •Primary IMHA/IMTP cases had better survival to discharge than secondary cases (89% vs 44%, P=0.03; OR=13.3)
- •Elevated blood urea nitrogen (BUN) was associated with increased short-term mortality (OR=19.5, P=0.009)
- •Survivors had significantly lower mean BUN (6.1±2.5 mmol/L) compared to non-survivors (9.9±3.1 mmol/L, P=0.003)