Case Presentation: A 15 year-old female with obesity presents to the hospital with vomiting, headache, and decreased responsiveness. Prior to arrival she had about 10 episodes of non-bloody vomiting, after which she had altered consciousness. She denied any diarrhea, dysuria, blood in stool, and vaginal bleeding. She denied bleeding and bruising easily. No recent consumption of raw meat.Physical exam was significant for petechiae on the lower legs and abdomen and altered mental status – she was following commands but non-verbal. Initial labs showed severe anemia with Hgb 6.4 g/dL, thrombocytopenia (platelets 10 x 109/L), and leukocytosis (13.4 x 109/L, 86% neutrophils). Due to schistocytes on blood smear and Coombs-negative hemolysis, she showed evidence of microangiopathic hemolytic anemia (MAHA). GFR and creatinine as well as coagulation studies were normal.Given fever, MAHA, thrombocytopenia, and altered mental status, suspicion was high for thrombotic thrombocytopenic purpura (TTP), and arrangements were made to start treatment with plasma exchange (PEX) urgently. Over the course of treatment with daily PEX and steroids, her mental status returned to baseline; her platelet count improved and eventually normalized at time of discharge. She continued to have no evidence of renal insufficiency. Lupus serologies came back negative. Her ADAMTS13 level later resulted as <5% and ADAMTS13 inhibitor was positive, confirming a diagnosis of acquired TTP.

Discussion: We describe a case of an adolescent with acquired TTP (aTTP) characterized by severe ADAMTS13 deficiency (<5% activity) in the presence of anti-ADAMTS13 autoantibodies. TTP is a life-threatening disorder belonging in the category of primary thrombotic microangiopathy (TMA) syndromes. It requires early and specific management with PEX therapy, without which, it is almost always fatal. Childhood-onset acquired TTP is extremely rare; as of 2016, only 89 cases of childhood acquired TTP have been reported worldwide. The literature describing it thus far underscores that it is most often misdiagnosed, further posing a problem and increasing the risk of progression of the disease. Unlike hereditary TTP, which is more common in the pediatric population, acquired TTP is distinguished by the detection of an inhibitory autoantibody to ADAMTS13.The classic pentad of TTP has been shown to very rarely occur in entirety, but this fact does not have to hinder diagnosis, even in a pediatric patient. Labs revealing MAHA and thrombocytopenia alone can lead to the presumptive diagnosis, and this guides and expedites treatment with PEX. While supportive care with platelet transfusions is a mainstay in the treatment of the more common pediatric TMA entity, hemolytic uremic syndrome, it can be harmful in TTP. It is worthwhile noting that misdiagnosis led to 22% of one of the largest cohorts of children with aTTP to get platelet transfusions. ADAMTS13 level allows for diagnostic confirmation but is a send-out lab that takes days to return and thus has no role in acute management.

Conclusions: Acquired TTP is a fatal, very rarely encountered disease process in pediatrics, and literature indicates providers are vulnerable to misdiagnosis and delay in treatment. Hospitalists must be aware of diagnostic criteria and maintain a high level of suspicion for this disorder. The mainstay of management remains plasma exchange and early and prompt initiation can provide improved outcomes.