Educational Case: Differentiating Thrombotic Thrombocytopenic Purpura From Other Thrombotic Microangiopathies and Potential Role of the Spleen

Abstract

The following fictional case is intended as a learning tool within the Pathology Competencies for Medical Education (PCME), a set of national standards for teaching pathology. These are divided into three basic competencies: Disease Mechanisms and Processes, Organ System Pathology, and Diagnostic Medicine and Therapeutic Pathology. For additional information, and a full list of learning objectives for all three competencies, see http://journals.sagepub.com/doi/10.1177/2374289517715040.¹.

Keywords: coagulation disorders; hematopathology; hemolytic uremic syndrome; organ system pathology; pathology competencies; platelets; spleen; thrombotic thrombocytopenic purpura.

Figure 1.

The patient’s peripheral blood smear. Image (A) shows schistocytes (arrow) as well as reticulocytes (arrowhead). Image (B) shows additional examples of schistocytes (arrow). Note that platelets are not well seen in either image.

Figure 2.

Histologic sections of the patient’s spleen. Image (A) shows retained splenic architecture with a lymphoid follicle (left, “*”) adjacent to an arteriole (“**”). The splenic red pulp (right side of image) includes splenic cords and sinusoids. At higher power within the red pulp (B), focal extramedullary hematopoiesis is appreciated with scattered megakaryocytes (arrowhead) and small erythroid islands. An immature erythroid element as identified by its condensed chromatin and very round nucleus is identified by an arrow. Scattered hemosiderin-laden macrophages were also present but are not as well appreciated in these images.