Non-regenerative anemia and immunodeficiency in a Fell pony foal

A five-week-old Fell Pony colt presented to the Large Animal Internal Medicine service at the Cornell University Hospital for Animals for evaluation of lethargy, fever, diarrhea and profound anemia of approximately one week's duration. A packed cell volume (PCV) of 10% was measured by the referring veterinarian on the day of presentation. This colt's history, signalment, and clinical presentation with severe anemia, fever, diarrhea, and abnormal chewing motions are consistent with a syndrome of anemia, immunodeficiency, and peripheral ganglionopathy reported in Fell Pony foals in the United Kingdom. Affected foals are normal at birth, but develop severe non-regenerative anemia and opportunistic infections secondary to a B lymphocytopenia; all known affected foals have died or been euthanized due to complications related to immunodeficiency, septicemia or severe anemia. Given the history, signalment, clinical presentation, and initial laboratory data, we were suspicious of Fell Pony Syndrome (FPS) in this colt, but as a case of FPS had never before been reported in North America, further testing was required to confirm this diagnosis. Results of abdominal and thoracic ultrasonography, fecal floatation, complete blood count, serum chemistry panel, urinalysis, Coomb?s test, bone marrow aspirates, and immunologic testing in this case were consistent with findings in FPS cases in the United Kingdom, and a diagnosis of Fell Pony Syndrome was thus made in this colt