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Evans syndrome (ES) describes an immune dysregulation syndrome manifesting as multilineage autoimmune cytopenias, most often autoimmune hemolytic anemia (AIHA) and immune thrombocytopenia (ITP), but also autoimmune neutropenia (AIN) in some cases. Since Evans and colleagues first described this phenomenon in the 1940s–1950s, this syndrome of immune cytopenias is increasingly identified to be secondary to underlying systemic immune dysregulation rather than idiopathic pathology. Some of the most common pathologies now known to drive ES include autoimmune lymphoproliferative syndrome (ALPS), common variable immunodeficiency (CVID), and other systemic autoimmune diseases such as systemic lupus erythematosus (SLE), particularly in adolescent females. These pathologies share the commonality of a dysregulated immune system in which autoreactive lymphocytes are poorly controlled, ultimately predisposing to autoimmunity. Importantly, clinical outcomes for patients with ES can be optimized by targeting specific immune dysregulation pathologies, underscoring the need for thorough individualized diagnostic and treatment strategies.

Immune thrombocytopenia (ITP) often presents clinically as petechiae, bruising, and/or mucocutaneous bleeding with an acute onset. Severe bleeding at the time of presentation is rare but can be life threatening. A detailed clinical history, including a review of the patient’s family history, is important to assess for possible inherited and/or secondary causes of thrombocytopenia (see Chap. 1). The physical examination reveals an otherwise healthy individual with skin bruising, purpura, and/or petechial rash in the absence of other findings, specifically lymphadenopathy or hepatosplenomegaly, or other systemic signs/symptoms such as fever, fatigue, weight loss, malaise, and/or pain. The diagnosis of primary ITP is one of exclusion and relies on ruling out other causes of thrombocytopenia in addition to a careful review for conditions associated with secondary ITP. The initial investigations often show severe thrombocytopenia, with variable to high mean platelet volume (MPV). In otherwise typical presentations, no additional testing is needed. The role of bone marrow testing remains controversial and is generally reserved for patients with an uncertain diagnosis or an atypical course.