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)

• Abnormal color of urine (blood in the urine)
• Abnormal menstrual periods
  • Heavy menstrual periods
  • Prolonged menstrual bleeding (more than 5 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
  • Bruises
  • Pinpoint red spots (petechiae)

• Bleeding time
• Platelet aggregation test
• Platelet count
• PT and PTT

Treatment is aimed at the cause of the problem.

• Bone marrow disorders (which have abnormally high numbers of platelets) are treated with platelet transfusions or by removing platelets from the blood and replacing them with donated platelets (plateletpheresis)
• Kidney failure is treated with dialysis or a drug called ddAVP
• Platelet problems caused by medication are treated by stopping the medication

Treating the cause of the problem usually corrects the defect.

• Prolonged bleeding
• Severe anemia

Call your health care provider:

• If you have bleeding and do not know the cause
• If your symptoms get worse or do not improve after you are treated for an acquired platelet function defect

Using medications carefully can reduce the risk of drug-related acquired platelet function defects. Treating other disorders may also reduce the risk. Some cases are not preventable.

McMillan R. Hemorrhagic disorders: Abnormalities of platelet and vascular function. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 179.