Other causes of hemolytic anemia including medications, microangiopathic hemolytic anemia (MAHA), and infections (commonly malaria, babesiosis, nontyphoidal salmonella, E coli, HIV) should be ruled out. This patient had a low likelihood of drug-induced hemolysis and no signs of protozoal or bacterial infection. MAHA is a rare but known hematologic manifestation of SLE that has been documented in case reports throughout the world; it was in the differential diagnosis for the patient in this case. This type of anemia is characterized by intravascular hemolysis, and laboratory findings include normocytic anemia, thrombocytopenia, low haptoglobin level, increased LDH level, and increased indirect bilirubin level.
Thrombotic thrombocytopenic purpura (TTP) is one of the primary thrombotic microangiopathy syndromes that cause MAHA. TTP is diagnosed based on clinical judgement and can affect multiple organ systems, including the neurologic, gastrointestinal, and renal systems. The entire classic pentad of thrombocytopenia, MAHA, neurologic abnormalities, renal dysfunction, and fever is rarely seen. In fact, this pentad was seen in only 5% of patients in data collected from the Oklahoma TTP-hemolytic-uremic syndrome (HUS) registry. Out of 65 patients with a first episode of TTP, the most common initial presenting feature was gastrointestinal symptoms (pain, nausea, vomiting, diarrhea) followed by neurologic abnormalities (seizure, stroke, coma, confusion, headache).
TTP is typically defined by a deficiency of ADAMTS13, a metalloprotease enzyme that cleaves von Willebrand factor. This could be hereditary through a genetic mutation or acquired through an autoantibody. However, measurements of ADAMTS13 are not required for diagnosis or for critical initial management decisions in TTP.
SLE and TTP are both rare diseases; thus, one can understand why SLE-associated TTP is an even rarer disease entity. One study identified only 56 such cases from 1968 to 2002. The many overlapping clinical and laboratory features also make diagnosing TTP in patients with SLE difficult. Patients may be diagnosed with TTP following an established SLE diagnosis, but patients may also develop SLE following recovery from an episode of TTP. One case series found that TTP in association with SLE appears to be underdiagnosed and that a positive Coombs test finding does not rule out diagnosis of TTP in this setting.
Another study from Toronto followed the course of 35 children with TTP and found that nine (26%) met the criteria for SLE, with an additional eight having features consistent with an incomplete lupus phenotype. Some case reports of patients with TTP-associated SLE had normal or near-normal ADAMTS13 activity, suggesting a possible different pathogenetic mechanism than what occurs in TTP. Nonetheless, identifying and initiating treatment with plasma exchange for TTP early in patients with suspected exacerbation of SLE can be life-saving.
Recently, caplacizumab, a monoclonal antibody directed against von Willebrand factor, was introduced as a treatment for TTP. When added to standard treatment with plasma exchange and high dose corticosteroids, caplacizumab reduces thrombotic events and improves outcomes. This drug was not available at the time the patient in the case was treated.
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