Chapter 10 Purpura Haemorrhagica Flashcards
What is purpura hemorrhagica (PH)?
An acute, non-contagious, aseptic necrotizing vasculitis characterized by edema and petechial or ecchymotic hemorrhage of the mucosa and subcutaneous tissue.
What causes vasculitis in purpura hemorrhagica?
Deposition of antigen-antibody immune complexes on blood vessel walls.
What infections are commonly associated with purpura hemorrhagica?
Streptococcus equi subsp. equi, equine influenza, equine viral arteritis, equine herpesvirus type 1, Streptococcus equi subsp. zooepidemicus, Rhodococcus equi, and Corynebacterium pseudotuberculosis.
What are the typical clinical signs of purpura hemorrhagica?
Urticaria, pitting edema of the distal limbs, head and ventrum, petechial/ecchymoses of mucosal membranes, anorexia, lethargy, weight loss, depression, fever, tachycardia, tachypnea, stiffness, and reluctance to move.
What are the severe complications of purpura hemorrhagica?
Severe pneumonia, cardiac arrhythmias, renal failure, gastrointestinal complications, or severe muscle infarctions.
What is the role of IgA in purpura hemorrhagica?
High IgA titers have been reported in horses with PH, suggesting its involvement in the disease pathophysiology.
What are the proposed hypotheses for high IgA and low IgG levels in PH?
Uncontrolled B cell expansion, liver failure to remove IgA, delayed IgG production, defective or suppressed IgG production, and neutralization or excess utilization of IgG.
What histological findings are characteristic of leukocytoclastic vasculitis in PH?
Presence of an inflammatory infiltrate of neutrophils, nuclear fragmentation, extravasation of erythrocytes, and necrosis of vessel walls.
What are the key features of leukocytoclastic vasculitis?
Small-vessel inflammatory disease mediated by deposition of antibody-antigen immune-complexes, characteristic of hypersensitivity type III.
What diagnostic methods are used for purpura hemorrhagica?
History of recent respiratory infection, clinical signs, skin biopsy, and exclusion of other causes of vasculitis.
What are common blood work findings in horses with purpura hemorrhagica?
Mild to moderate anemia, leukocytosis, neutrophilia, hyperproteinemia, hyperglobulinemia, and hyperfibrinogenemia.
What treatment protocol is recommended for purpura hemorrhagica?
Reducing inflammation with corticosteroids, removing the inciting cause, providing supportive care, and using antimicrobials like penicillin.
What are the common drugs used for treating PH and their dosages?
Flunixin meglumine (1.1 mg/kg BID), phenylbutazone (2.2 mg/kg BID), dexamethasone (0.05–0.25 mg/kg BID or SID), and prednisolone (0.5–2 mg/kg BID or SID).
What supportive care measures are important in managing PH?
Bandaging swollen legs, caring for wounds, cold hydrotherapy, intravenous fluids, and tracheotomy if needed.
What is the prognosis for horses with purpura hemorrhagica?
Prognosis improves with early and aggressive treatment, with an estimated case fatality rate of 10% with appropriate treatment.
What are the common histological features of leukocytoclastic vasculitis in PH?
Neutrophil perivascular infiltration with pyknosis and karyorrhexis, extravasation of erythrocytes, and vessel wall necrosis.
What are the potential complications of prolonged immunosuppressive therapy in PH?
Increased risk of infections, laminitis, gastrointestinal issues, and delayed wound healing.
What are the common clinical signs of systemic involvement in PH?
Colic, diarrhea, respiratory distress, and severe muscle infarctions.
What are the typical clinical signs of severe head edema in PH?
Difficulty in breathing and eating, leading to anorexia, lethargy, and weight loss.
What is the role of antimicrobial therapy in PH?
Treating underlying infections, especially with Streptococcus equi, using penicillin or other antimicrobials like trimethoprim-sulfamethoxazole and ceftiofur.
What is the significance of elevated IgA titers in PH?
Elevated IgA titers to Streptococcus equi are suggestive of PH and may indicate an immune response to the infection.
What is the role of anti-thrombotic agents in PH treatment?
Preventing thromboembolic complications using agents like pentoxifylline, low molecular weight heparin, and acetylsalicylic acid.
What are the differential diagnoses for vasculitis in horses?
Drug or vaccine response, pastern and cannon leukocytoclastic vasculitis, photo-activated vasculitis, equine viral arteritis, equine infectious anemia, and others.
What is the significance of early diagnosis and treatment in PH?
Improves prognosis, reduces complications, and prevents severe outcomes.
What are the potential long-term outcomes for horses that recover from PH?
Generally good with appropriate treatment, but monitoring for recurrence and managing long-term complications is necessary.
What is the importance of avoiding vaccination in horses with high SeM antibody titers?
To prevent triggering purpura hemorrhagica in horses with elevated antibody levels to Streptococcus equi.
What are the common side effects of corticosteroid therapy in PH?
Laminitis, immunosuppression, and gastrointestinal issues.
What are the clinical signs of purpura hemorrhagica?
Edema, petechial hemorrhage, anorexia, lethargy, weight loss, depression, fever, tachycardia, tachypnea, stiffness, and reluctance to move.
What are the common histological findings in a skin biopsy of a horse with PH?
Leukocytoclastic vasculitis, neutrophil infiltration, nuclear fragmentation, extravasation of erythrocytes, and vessel wall necrosis.
What are the typical blood work findings in horses with PH?
Mild to moderate anemia, leukocytosis, neutrophilia, hyperproteinemia, hyperglobulinemia, and hyperfibrinogenemia.
What is the treatment protocol for PH?
Reducing inflammation with corticosteroids, providing supportive care, and using antimicrobials to treat underlying infections.
What are the common drugs used for treating PH?
Flunixin meglumine, phenylbutazone, dexamethasone, and prednisolone.
What is the prognosis for horses with PH?
Prognosis improves with early and aggressive treatment, with an estimated case fatality rate of 10% with appropriate treatment.
What supportive care measures are important in managing PH?
Bandaging swollen legs, caring for wounds, cold hydrotherapy, and intravenous fluids.
What is the role of anti-thrombotic agents in PH treatment?
Preventing thromboembolic complications using agents like pentoxifylline, low molecular weight heparin, and acetylsalicylic acid.
What is the significance of elevated IgA titers in PH?
Elevated IgA titers to Streptococcus equi are suggestive of PH and may indicate an immune response to the infection.
What are the differential diagnoses for vasculitis in horses?
Drug or vaccine response, pastern and cannon leukocytoclastic vasculitis, photo-activated vasculitis, equine viral arteritis, equine infectious anemia, and others.
What is the importance of avoiding vaccination in horses with high SeM antibody titers?
To prevent triggering purpura hemorrhagica in horses with elevated antibody levels to Streptococcus equi.
What are the potential complications of prolonged immunosuppressive therapy in PH?
Increased risk of infections, laminitis, gastrointestinal issues, and delayed wound healing.
What are the clinical signs of systemic involvement in PH?
Colic, diarrhea, respiratory distress, and severe muscle infarctions.
What is the role of antimicrobial therapy in PH?
Treating underlying infections, especially with Streptococcus equi, using penicillin or other antimicrobials like trimethoprim-sulfamethoxazole and ceftiofur.
What are the common clinical signs of severe head edema in PH?
Difficulty in breathing and eating, leading to anorexia, lethargy, and weight loss.
What are the potential long-term outcomes for horses that recover from PH?
Generally good with appropriate treatment, but monitoring for recurrence and managing long-term complications is necessary.
What are the clinical signs of purpura hemorrhagica?
Edema, petechial hemorrhage, anorexia, lethargy, weight loss, depression, fever, tachycardia, tachypnea, stiffness, and reluctance to move.
