Here is an interesting case that presented to me recently. The referring veterinarian, owner and I had a strong cooperative relationship that resulted in an unusual diagnosis.
A 10-year-old National Show Horse gelding presented to the clinic for evaluation of multiple episodes of colic and fever over the preceding 3 months. He had also been treated for EPM 2 months prior. His neurologic signs responded to Marquis but the symptoms returned when the medication was discontinued.
On physical examination at the clinic, he was blind in the right eye, grade 2 ataxic and slightly icteric. An ophthalmic examination revealed retinal "butterfly" lesions compatible with previous uveitis. Gastroscopy revealed several grade 1 ulcers in the squamous epithelium at the margo plicatus. An ultrasound of the abdomen revealed hepatomegaly with choleliths. The GGT, AST and total bilirubin were elevated. A diagnosis of cholelithiasis, gastric ulceration, recrudescence of EPM and quiescent equine recurrent uveitis was made. Treatment with Marquis, Gastrogard and prolonged enrofloxacin resolved the majority of problems. However, the horse experienced a severe bout of uveitis the following week that resulted in anterior chamber hypopyon, retinal detachment and blindness in the left eye. In 4 months time, the uveitis progressively worsened and the fevers and the neurologic disease recurred. In a second visit to the clinic at that time, pneumonia and meningitis were diagnosed in addition to the ongoing uveitis.
Because of the multiple chronic disease processes, immunodeficiency was suspected. Blood was submitted to the Cornell Equine Immunology Laboratory for peripheral blood lymphocyte phenotyping and serum immunoglobulin concentration. The horse had complete B-cell depletion with IgM levels below the detectable range compatible with common variable immunodeficiency. Due to a grave prognosis, euthanasia was recommended. The horse died of bacterial meningitis and sepsis 1 week later.
Common variable immunodeficiency (CVID) was first described in 2002 by Dr. Julia Felippe at Cornell University. There have been only 19 reported cases to date. It is characterized by B cell lymphopenia or depletion, hypo- or agammaglobulinemia, impaired humoral response to tetanus toxoid vaccinations and recurrent bacterial infections and fevers. It is seen in adult horses (mean age of 10 years) of both genders in various breeds with unrelated bloodlines. The most common clinical signs are recurrent fevers and respiratory infections. Meningitis is not uncommon and is most likely due to septicemia. Concurrent uveitis has been reported in a small number of cases. The primary cause of CVID remains unknown. Several genetic mutations have been identified in humans however it does not follow a familial mode of inheritance. Repeated immunoglobulin infusion or bone marrow transplant gives humans a good prognosis. There is no treatment in the horse. Most horses die within 1 year of diagnosis. The incidence is most likely greater than reported. As veterinarians become more aware of CVID, testing and diagnosis will likely increase. For more information about CVID, visit the Cornell website.