The autoimmune cytopenias are a group of disorders resulting primarily from autoantibody-mediated destruction of blood cells, with variable clinical sequelae depending on the severity and lineage affected. Disease presentation ranges from an asymptomatic finding on a routine full blood count to an acutely unwell patient suffering the clinical consequences of severe anaemia, neutropenia or thrombocytopenia. The cytopenia may be primary or secondary to underlying infectious, immune or malignant processes. Thrombotic thrombocytopenic purpura (TTP) is a distinct, rare but potentially life-threatening entity that classically but not invariably presents with a pentad of acute onset haemolytic anaemia, thrombocytopenia, neurological symptoms, renal impairment and fevers. Autoimmune cytopenias have formed a recognised diagnostic entity for over 150 years yet continue to present a challenge in medical practice due to heterogeneity in clinical presentation and triggering factors, an incomplete understanding of underlying pathophysiology and a lack of evidence-based therapeutic approaches.