Approach to Thrombocytopenia in Older Adults
Thrombocytopenia, whether symptomatic or not, is a relatively common finding in clinical medicine. The causes of thrombocytopenia are many, and all of these may be found at all ages. However, just as the frequencies of these causes vary between pediatric and adult age-groups, so too is there variation between younger adults and older individuals. Also, the pathophysiological approach to thrombocytopenia (decreased production, increased destruction, sequestration, dilution) remains just as valid to the seasoned hematologist as to the neophyte. In this article, we provide a suggested approach to the patient with thrombocytopenia, with emphasis on the more common causes in older adults.
Key words: thrombocytopenia, platelets, bleeding disorders, primary hemostasis, older adults.
Introduction
Thrombocytopenia is defined as a platelet count below the normal range for the population (±2 standard deviations from the mean). In most laboratories, the normal platelet count in adults ranges from 150–450 x 109/L, with mean values of 237 x 109/L and 266 x 109/L in males and females, respectively. Thrombocytopenia is defined as a platelet count less than 150 x 109/L, keeping in mind that 2.5% of the normal population will have a platelet count lower than this.
Analogous to the red blood cell system, the major mechanisms for a reduced platelet count are decreased production (e.g., bone marrow failure) and increased destruction (e.g., drug-induced thrombocytopenia). Two additional mechanisms are distributional or sequestration (i.e., hypersplenism) and dilutional (i.e., massive transfusions) thrombocytopenia.
Thrombocytopenia in Older Adults in the Outpatient Setting
The commonest causes of thrombocytopenia in this scenario are listed in Table 1, together with less common or rare causes. Although it may seem surprising to some to see immune or “idiopathic” thrombocytopenic purpura (ITP) listed in the left-hand column, about one-quarter of the patient with ITP in our large hematology practice are over the age of 50.
Diagnostic Approach
Individuals with thrombocytopenia may be asymptomatic and thrombocytopenia may first be detected on a routine complete blood count. The symptomatic presentation of thrombocytopenia is bleeding, characteristically cutaneous and/or mucosal (Figure 1). Bleeding into the skin is manifested as petechiae or superficial ecchymoses. Mucosal bleeding may be manifest as epistaxis or gingival bleeding; large hemorrhagic bullae may appear on the buccal mucosa due to the lack of vessel protection afforded by the submucosal tissue. The pattern of bleeding in patients with thrombocytopenia (and in patients with disordered platelet function) differs from that seen in patients with coagulation disorders such as hemophilia, in that the latter group has delayed bleeding that begins several hours or a day after trauma, because normal platelet function can provide temporary hemostasis. Patients with coagulation disorders also have deep bleeding (into tissues, muscles, and joints), minimal bleeding after minor cuts, more delayed bleeding, more postsurgical bleeding, and tend not to have petechiae Certain drugs that affect the number or function of platelets are listed in Table 2. Of course, many older adults may be taking more than one of these drugs, in which case identifying the culprit may involve a combination of good clinical “hunch” with consultation of a pharmacopoeia, or even trial and error. We also recommend the article by George, et al., listed in our references.6
When thrombocytopenia is confirmed, a stepwise evaluation should be undertaken to assess the causes and the urgency of treatment. If diagnoses such as thrombotic thrombocytopenic purpura (TTP) or heparin-induced