A 49 y/o M presents with three days of bloody diarrhea, altered mental status and fever. Family members states he has been in his usual state of health previously. A CT head is unremarkable. His labs show Na 135 mEq/L, K 5.1 mEq/L, creatinine of 2.3 mg/dL, WBC 11, Hb 7 and platelets of 15. What test should be ordered to confirm the diagnosis? (scroll down for the answer)

a) Differential

b) Haptoglobin

c) Reticulocyte Count

d) Peripheral Smear

e) Lumbar Puncture

The correct answer is d) Peripheral Smear

The patient has Thrombotic Thrombocytopenic Purpura. Abnormal activity of ADAMST13 leads to a lack of the cleavage of von Willebrand factor leading to hemolytic anemia and platelet aggregation. Schistocytes are seen on the smear which makes the diagnosis. The PT, PTT and INR are normal which differentiates it from DIC. The treatment is plasmapheresis.