Acquired platelet function defects are diseases or conditions that cause the platelets (the blood cells essential for clotting) to not work properly. The term "acquired" means these diseases or conditions are not inherited, but rather develop independently in a person.

Platelet disorders can involve an abnormal number of these cells (too many or too few), or abnormal functioning of the platelets. Any platelet disorder affects blood clotting.

Disorders of platelet function can be caused by congenital (present at birth) diseases, or they can be acquired conditions. Acquired platelet function disorders involve abnormal platelet function. These disorders develop as a result of another disease or condition (acquired). In many cases, the platelet count may be normal or even high, but evidence of a bleeding disorder will be present. Bone marrow disorders such as primary thrombocytopenia, polycythemia vera, chronic myelogenous leukemia, and myelofibrosis can produce abnormalities in platelet function.

Other causes include renal failure, multiple myeloma, and medications such as aspirin and other anti-inflammatory drugs, penicillins, phenothiazines, and prednisone (after prolonged use).

• Abnormal color of urine (blood in the urine)
• Abnormal menstrual periods
  • Heavy menstrual periods
  • Prolonged menstrual bleeding (more than five days per menstrual period)
• Abnormal vaginal bleeding
• Bleeding under the skin or in the muscles (soft tissues)
• Gastrointestinal bleeding
  • Bloody, dark black, or tarry bowel movements
  • Vomiting blood or vomiting material that resembles coffee grounds
• Nosebleeds
• Prolonged bleeding, easy bruising
• Skin rash
  • Multiple lesions
  • Bruises
  • Pinpoint red spots

• Normal, high, or low platelet count
• Normal PT and PTT results
• Platelet aggregation test
• Prolonged bleeding time

Treatment is directed at the cause of the abnormality. Dialysis reduces the bleeding tendency if the cause is renal failure. Platelet transfusions or plateletpheresis (removal of platelets from the blood and replacement with donated platelets) may be needed in bone marrow disorders. Medication-induced platelet abnormalities require stopping the medication.

Treatment of the cause of the abnormality usually corrects the defect.

• Prolonged bleeding
• Severe anemia

Call your health care provider:

• If bleeding of unknown cause is present
• If symptoms worsen, or do not improve, after treatment of an acquired platelet function defect

Care in the use of medications can reduce the risk of drug-related acquired platelet function defects. Treatment of other disorders may also reduce risk. Some cases are not preventable.

Hoffman R, Benz Jr. EJ, Shattil SJ, et al.. Hematology: Basic Principles and Practice. 4th ed. Philladelphia, Pa: Churchill Livingston; 2005.

McPherson RA and Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 21st ed. Philadelphia, Pa: WB Saunders; 2007:762-64.