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Platelet Dysfunction 790.e5

• Dogs may bring plague-infected fleas into Foster CL, et al: Sick as a dog. N Engl J Med RELATED CLIENT EDUCATION
372:1845-1850, 2015.
households; sleeping with dogs may increase Nichols MC, et al: Yersinia pestis infection in dogs: 62 SHEETS
VetBooks.ir SUGGESTED READING Pennisi MG, et al: Yersinia pestis infection in cats: Consent to Perform Fine-Needle Aspiration Diseases and Disorders
the human risk of acquiring the disease.
cases (2003-2011). J Am Vet Med Assoc 244(10):
176-180, 2014.
of Masses
Sykes, JE et al: Yersinia pestis (plague) and other
yersinioses. In Sykes JE, editor: Canine and feline ABCD guidelines on prevention and management. Pneumonia
J Feline Med Surg 15:582-584, 2013.
infectious diseases, ed 1, St. Louis, 2014, Elsevier, AUTHOR: Khristen J. Carlson, DVM, MS
pp 531-536. EDITOR: Joseph Taboada, DVM, DACVIM
ADDITIONAL SUGGESTED
READINGS
Chomel BB: Plague. In Greene CE, editor: Infectious
diseases of the dog and cat, ed 4, St. Louis, 2012,
Saunders, pp 469-476.

Platelet Dysfunction

BASIC INFORMATION • Hematuria, epistaxis, melena, persistent should consider platelet dysfunction as a cause
posttraumatic bleeding for clinical signs mentioned above.
Definition Hereditary:
The hemostatic defect is caused by impaired • Recurrent mucosal bleeds and ecchymoses, Differential Diagnosis
platelet activation response. Platelet dysfunction prolonged bleeding from loss of deciduous • Thrombocytopenia
is broadly classified as acquired or hereditary; teeth or minor wounds, excessive bleeding • Hereditary or acquired coagulation factor
hereditary defects are less common. during proestrus, blood-loss anemia after deficiencies
surgery or trauma • Von Willebrand disease
Synonyms • Vasculopathy or erosive/infiltrative vessel
Thrombocytopathia, thrombopathia PHYSICAL EXAM FINDINGS defect
• Petechiae and ecchymoses • Defect of fibrinolysis
Epidemiology • Abnormal bleeding from traumatic/surgi-
SPECIES, AGE, SEX cal wounds and catheter and venipuncture Initial Database
• Acquired: depends on the underlying disease sites • Physical exam (including funduscopic and
or treatment • Mucosal hemorrhage (epistaxis, gingival rectal exam) to differentiate systemic from
• Hereditary: dogs and cats of both sexes; severe hemorrhage, melena, hematuria) localized or focal site of hemorrhage
defects typically manifest by 1 year of age • Platelet count: usually normal for patients
Etiology and Pathophysiology with hereditary platelet dysfunction
GENETICS, BREED PREDISPOSITION Acquired: often multifactorial due to intrinsic • Coagulation screening tests, such as acti-
• All hereditary thrombocytopathias are auto- changes in platelet metabolism or extrinsic vated partial thromboplastin time (aPTT),
somal, with recessive or unknown expression alterations in blood viscosity: prothrombin time (PT), ± activated clotting
patterns. • Platelet effects of NSAIDs such as aspirin time (ACT): usually normal
• Affected dog breeds: basset hound, boxer, are irreversible (i.e., effects last as long as • CBC, serum biochemistry profile, urinalysis
cocker spaniel, collie, German shepherd, the platelet life span: several days), whereas to define acquired disorders
Great Pyrenees, Greater Swiss mountain others (e.g., colloids/plasma expanders) ○ Avoid cystocentesis and jugular
dog, Landseer Newfoundland, otterhound, inhibit platelet function while the drug or venipuncture.
spitz compound is in circulation. • Thorough history of drug or dietary supple-
• Affected cat breeds: Persian cat, domestic Hereditary defects: pathophysiologic classification: ment administration
shorthair cat • Membrane glycoprotein (GP) disorders: most
common is thrombasthenic thrombasthenia Advanced or Confirmatory Testing
RISK FACTORS or Glanzmann’s thrombasthenia (fibrinogen • Buccal mucosal bleeding time: usually
Acquired platelet dysfunction associations: receptor [GP IIb/IIIa] defects) increased (normal: 2-4 minutes) (p. 1076)
• Systemic disease (anemia, uremia, liver • Secretory granule (storage pool) defects • Platelet morphology review
failure, hyperproteinemia) • Signal transduction defects • Point-of-care hemostasis analyzer: the
• Drug therapy (nonsteroidal antiinflammatory • Platelet procoagulant deficiency PFA100 platelet function analyzer (Dade-
drugs [NSAIDs], heparin, plasma expanders, Behring, Deerfield, IL) is a tabletop instru-
sulfonamides, clopidogrel) DIAGNOSIS ment that measures platelet adhesion and
• Disseminated intravascular coagulation aggregation in whole blood samples. The
(DIC) Diagnostic Overview test endpoint (closure time) is sensitive to
Thrombocytopenia and von Willebrand disease platelet adhesion and aggregation defects in
Clinical Presentation (p. 1043) are the most common acquired and dogs, but anemia, thrombocytopenia, and
HISTORY, CHIEF COMPLAINT hereditary primary hemostatic defects, respec- low plasma von Willebrand factor levels also
Acquired: tively. Along with ruling out these disorders, cause prolonged closure time.
• Mild to moderate bleeding tendency accom- disorders of the coagulation cascade (coagula- • Platelet testing for in-depth classification of
panying a primary disease or drug therapy tion profile) and vascular integrity, clinicians hereditary defects (requires referral):

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