Disorders of Blood Coagulation and Thrombocytopenia

Thrombocytopenia and Purpura

• Platelet count can be as low as 20,000/mm3
• Bone marrow examination shows a normal number of megakaryocytes

Henoch-Schönlein Syndrome

• Caused by increased vessel permeability, leading to bleeding in small blood vessels
• Occurs most frequently in children between 2 and 8 years old
• More frequent in boys than girls
• Usually, there is a history of a mild infection before the outbreak of symptoms
• Presents as a possible platelet disorder until a differential diagnosis is made
• Assessment:
  • Purpural rash on buttocks, posterior thighs, and extensor surface of arms and legs
  • Rash begins as urticarial lesions that change to pink maculopapules
  • Joint tenderness and swelling
  • Gastrointestinal symptoms
  • Gross or microscopic hematuria may be present
  • Biopsy shows granulocytes in small arteriole walls
• Therapeutic management:
  • Oral corticosteroid therapy (prednisone)
  • Mild analgesics for a short period
  • Nose and throat cultures to rule out bacterial involvement
  • Urine assessment for protein and glucose to detect kidney involvement
  • Disease typically runs a course of 4 to 6 weeks
  • Complication: mild chronic nephritis

Hemophilias

• Inherited disorders of blood coagulation
• Types: each involving a deficiency of a different blood coagulation factor
• Hemophilia A (Factor VIII Deficiency):
  • Caused by deficiency of the coagulation component factor VIII
  • Transmitted as a sex-linked recessive trait
  • Factor VIII is an intrinsic factor of coagulation

Disorders of Blood Coagulation

• Platelets are necessary for blood coagulation
• Disorders that limit the number of platelets limit the effectiveness of this process
• Normal platelet level: 150,000/mm3
• Thrombocytopenia (decreased platelet count): less than 40,000/mm3
• Thrombocytopenia often leads to purpura or blood seeping from vessels into the skin

Purpuras

• Refers to a hemorrhagic rash or small hemorrhages in the superficial layer of skin
• Two main types: idiopathic thrombocytopenic purpura and Henoch-Schönlein syndrome

Idiopathic Thrombocytopenic Purpura

• Result of a decrease in the number of circulating platelets in the presence of adequate megakaryocytes
• Cause is unknown, but thought to result from an increased rate of platelet destruction due to an antiplatelet antibody
• Assessment:
  • Manifestations often begin abruptly
  • Miniature petechiae or large areas of asymmetric ecchymosis
  • Epistaxis or bleeding into joints may be present
  • Laboratory studies reveal marked thrombocytopenia