Mohammed E. Hussain, Department of Medicine, Mount Sinai Hospital, Toronto, ON.
Dominick Amato, Department of Medicine, Mount Sinai Hospital; Department of Medicine, University of Toronto, Toronto, ON.

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.

D'Arcy Little, MD, CCFP
Director of Medical Education,
York Community Services, Toronto, ON.

Introduction
Thrombocytopenia is a common hematologic problem in the elderly.¹ A classic survey indicated that over 50% of patients with thrombocytopenia were over 50 years of age, and 25% were over 70 years of age.² The elderly patient with thrombocytopenia presents the clinician with both diagnostic and management challenges. Because the disorders and mechanisms that lead to decreased numbers of platelets in the circulation are varied, the spectrum of differential diagnoses is broad and includes decreased platelet production and accelerated destruction.³ In addition, the clinical implications of thrombocytopenia fall into a wide spectrum, from a benign condition picked up incidentally in an asymptomatic patient to a life-threatening disorder.⁴ The following article will present an approach to the evaluation of thrombocytopenia in the elderly patient (Figure 1).

Definition and Clinical Significance
Thrombocytopenia is a condition in which there is a deficient number of circulating platelets. The cutoff for diagnosis is 150 x 10⁹/L of blood, which represents the platelet count two standard deviations below the mean obtained when sampling a large number of persons from the general population.