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

With platelet disorders, there may be too many or too few platelets, or platelets that do not function well. Any platelet disorder affects blood clotting.

These disorders can be caused by diseases that are present at birth (congenital), or they may develop because of another disease or condition. In many cases, the platelet count may be normal or even high, but there will be evidence of a bleeding disorder.

Disorders that can cause problems in platelet function include:

• Chronic myelogenous leukemia
• Myelofibrosis
• Polycythemia vera
• Primary thrombocythemia

Other causes include:

• Kidney (renal) failure
• Multiple myeloma
• Medications such as aspirin, ibuprofen and other anti-inflammatory drugs, penicillins, phenothiazines, and prednisone (after long-term use)