Acquired platelet function defects are non-hereditary diseases or associated conditions that cause the platelets (the blood cells essential for coagulation) to not function properly.

Platelets are blood cells that are essential for blood clotting. Platelet disorders can involve an inappropriate number (too many or too few) or improper functioning of the platelets. Any platelet disorder affects blood clotting.

Disorders of platelet function can be caused by congenital (present at birth) diseases or acquired conditions. Acquired platelet function disorders involve improper platelet function. They develop as a result of another disease or condition (acquired). In many cases, the platelet count may be normal or even elevated, but evidence of a bleeding disorder will be present. Myeloproliferative 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 medications, penicillins, phenothiazines, and prednisone (prolonged use).

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

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

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 indicated in myeloproliferative disorders. Medication-induced platelet abnormalities require discontinuation of the medication.

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

• Prolonged bleeding
• Severe anemia

• 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.