New-onset acute thrombocytopenia in hospitalized patients: pathophysiology and diagnostic approach

Abstract

Thrombocytopenia is a hematological finding commonly encountered in daily clinical practice from asymptomatic clinic patients to critically ill intensive care unit patients. A broad spectrum of etiologies and variation in clinical presentation often present a diagnostic challenge. Furthermore, concomitant presence of thrombosis and thrombocytopenia, as in cases of thrombotic thrombocytopenia, complicates the management. In hospitalized patients, new-onset thrombocytopenia is an important reason for hematology consultation. Therefore, it is of utmost importance that the etiology is diagnosed accurately. In addition, a basic understanding of the pathophysiology and the differential diagnosis avoids delay in the diagnosis and leads to rapid initiation of treatment. This review will address causes of thrombocytopenia that arises in hospitalized patients with an emphasis on the pathophysiological basis of each disorder.

Keywords: Thrombocytopenia; hospital acquired; pathophysiology; thrombopoiesis; thrombopoietin.

Figure 1.

Thrombopoiesis begins in the bone marrow milieu with the differentiation of pleuripotent stem cell to megakaryocytes. Several key regulators (TPO, interleukins, B12, folate, NF-κB) are involved in platelet formation. Platelets have several destinations in the peripheral circulation including self-regulated apoptosis, consumption in response to injury, splenic sequestration, and platelet destruction. Causes of decreased platelet production (yellow box) and increased peripheral destruction (red box) are shown. Abbreviations: MDS (myelodysplastic syndrome), TPO (thrombopoietin), IL (interleukin), SCF (stem cell factor), NF-κB (nuclear factor kappa B), DIC (disseminated intravascular coagulation), HELLP (hemolysis, elevated liver enzymes and low platelets).

Figure 2.

An algorithmic approach to hospital-induced thrombocytopenia. Abbreviations: DIC (disseminated intravascular coagulation), TTP (thrombotic thrombocytopenic purpura), ST-HUS (Shiga toxin-mediated hemolytic uremic syndrome), aHUS (atypical hemolytic uremic syndrome), CPB (cardiopulmonary bypass), IABP (intraaortic balloon pump), HIT (heparin-induced thrombocytopenia), DITP (drug-induced immune thrombocytopenia), HELLP ((hemolysis, elevated liver enzymes, and low platelets), PTP (post transfusion purpura).

Figure 3.

Peripheral smear examination demonstrating, (a) small scattered platelet clumps; (b) platelet satellitism where platelets are arranged in a rosette-like pattern around the neutrophils; (c) schistocytes, bite cells, and scarcity of platelets, (d) a giant platelet almost the size of a red blood cell.