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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • A chronic, progressive condition of unclear etiology associated with weight loss, dermatitis, and the presence of eosinophilic infiltrates in multiple organs
  • Similar conditions exist in humans, cats, and dogs. Parasitic, allergic, autoimmune, viral, and toxic causes have been implicated. The coexistence of T-cell lymphosarcoma and the syndrome in horses suggests that the production of cytokines (such as interleukin 5) by clonal neoplastic cells stimulates production and proliferation of eosinophils
  • Skin, GI, hepatobiliary, and respiratory systems are affected

Signalment!!navigator!!

  • Standardbreds may be predisposed
  • Horses 3–13 years of age

Signs!!navigator!!

  • Most horses present with weight loss of several weeks’ or months’ duration, although a few cases have presented acutely. Roughly half of these horses will have diarrhea concurrently
  • Examination often shows concomitant crusting, pruritic and exfoliating dermatitis, and alopecia. Skin lesions are most commonly found on the distal limbs, coronary bands, and head, or are generalized

Causes and Risk Factors!!navigator!!

Multiple etiologies have been proposed, including parasitism, hypersensitivity, and T-cell lymphosarcoma. An underlying cause is often not identified and the pathogenesis is unknown.

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

Tissue biopsy and laboratory testing help differentiate this disease from other diseases that present with similar signs such as:

  • Causes of chronic weight loss, including dental problems, poor nutrition, parasitism, and infiltrative bowel diseases, including alimentary lymphosarcoma
  • Causes of dermatitis, including dermatophilosis, dermatophytosis, pyoderma, and autoimmune skin diseases
  • Sarcoidosis (not to be confused with the common equine skin tumor) can cause weight loss and skin lesions, but may be differentiated by tissue biopsy

CBC/Biochemistry/Urinalysis!!navigator!!

  • Hypoproteinemia
  • Hypoalbuminemia
  • Hyperfibrinogenemia
  • Hypereosinophilia
  • Evidence of other organ involvement including increased γ-glutamyltransferase, alkaline phosphatase, or creatinine

Other Laboratory Tests!!navigator!!

Abdominocentesis may reveal a modified transudate containing eosinophils.

Imaging!!navigator!!

  • Thoracic radiographs may reveal patterns consistent with miliary or granulomatous infiltrates
  • Ultrasonography of liver, spleen, or kidneys may show granulomatous changes

Other Diagnostic Procedures!!navigator!!

  • Tissue biopsy (GI tract, liver, lungs)—multifocal or diffuse eosinophilic and lymphoplasmacytic infiltrates
  • Bone marrow biopsy may have large clusters of proliferating eosinophils or precursors
  • Skin biopsy for histopathology—ulceration and acanthosis with infiltrating neutrophilic and lymphocytic exudate and eosinophilic granulomas
  • Glucose or xylose GI absorption test—may be abnormal
  • Exploratory laparotomy findings may include multifocal nodules or diffuse thickening of the GI tract due to eosinophilic and lymphocytic infiltration. Focal or disseminated lymphosarcoma may be found

Treatment ⬆ ⬇

TREATMENT

  • Outpatient medical treatment may be appropriate, although horses with severe diarrhea or other organ system dysfunction may require hospitalization with fluid therapy and supportive care for diarrhea and skin lesions. Rest affected horses
  • Encourage appetite. The diet should be modified to optimize absorption, including increasing high-quality forage and caloric intake (by increasing both the amount of feed and caloric density through fat supplementation)
  • Consider exploratory laparotomy to obtain tissue biopsies, to rule out other intestinal involvement, or to resect a primary alimentary lymphosarcoma

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

Attempt treatment with dexamethasone (0.05–0.1 mg/kg IV or PO daily, reducing over several weeks) or other anti-inflammatory medications. In 1 report, the condition resolved with dexamethasone, trimethoprim–sulfamethoxazole, hydroxyzine hydrochloride, and fenbendazole.

Contraindications/Possible Interactions!!navigator!!

None

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Monitor the horse's weight
  • Monitor response to medication through examination, hematology, biochemistry, and/or imaging

Expected Course and Prognosis!!navigator!!

The disease is associated with a poor prognosis and low survival. Most horses require euthanasia after several months of poor response to treatment, although a few reported cases have responded well and survived longer than 8 months after diagnosis.

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Associated Conditions!!navigator!!

Lymphosarcoma

Synonyms!!navigator!!

  • Hypereosinophilic syndrome
  • Multisystemic eosinophilic epitheliotrophic disease

Abbreviations!!navigator!!

GI = gastrointestinal

Suggested Reading ⬆ ⬇

Bosseler L, Verryken K, Bauwens C, et al. Equine multisystemic eosinophilic epitheliotropic disease: a case report and review of literature. N Z Vet J 2013;61:177–182.

Author(s) ⬆

Author: Laura K. Dunbar

Consulting Editor: Gwendolen Lorch

Acknowledgment: The author and editor acknowledge the prior contribution of Richard J. Piercy.