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