Introduction

Thrombotic thrombocytopenic purpura (TTP) is a disseminated form of thrombotic microangiopathy that was initially described by Moschowitz in 1924 as a new disease. He reported an abrupt onset of petechiae, anemia and microscopic hematuria in a 16-year-old girl, who presented with fever and malaise and died 13 days later. He observed widespread hyaline microthrombi in the terminal arterioles and capillaries and interpreted them as agglutinated and hyalinized erythrocytes caused by ‘a powerful poison which had both agglutinative and hemolytic properties’. A congenital form of TTP was reported by Schulman et al., who suggested that the pathogenesis was due to deficiency of a platelet-stimulating factor in the patient's plasma. A similar congenital deficiency of a plasma factor, important in platelet and red-cell survival, was later described by Schulman in another patient with chronic relapsing TTP. Familial predisposition to TTP was implicated from observations of siblings suffering from recurrent TTP. The congenital form of TTP has been occasionally described in the literature as Upshaw–Schulman syndrome.

TTP is characterized by the pentad of severe thrombocytopenia, microangiopathic hemolysis with erythrocyte fragmentation, neurologic deficit, renal dysfunction, and fever. A TTP-like disorder, the hemolytic uremic syndrome (HUS), usually occurs in children, and is characterized by the triad of thrombocytopenia, microangiopathic hemolytic anemia and renal dysfunction. The diagnosis of TTP is usually made in adult patients with neurologic dysfunction, whereas children with predominant glomerular damage are preferably diagnosed as having HUS.