A 37-year-old woman has a 2-week history of intermittent headache and general malaise. Over the last 24 hours, she has developed back pain, hematuria, vomiting, fever, and confusion. She denies recent travel or insect bites. There is no history of dysuria, urgency, frequency, or kidney stones. Her oral temperature is 38°C and her heart rate is 100/min. Physical findings include pale conjunctivae, borderline tachycardia, bilateral costovertebral tenderness, and several purpuric skin lesions. Her urine dipstick is strongly positive for hemoglobin, but negative for nitrites and leukocyte esterase. The test that will most likely reveal the correct diagnosis is:
CBC with differential and peripheral smear.
Complete urinalysis with microscopic examination.
Liver function tests.
This patient exhibits classic signs and symptoms of thrombotic thrombocytopenic purpura (TTP), a microangiopathic hemolytic anemia (MAHA). TTP is a syndrome characterized by anemia, thrombocytopenia, fever, renal dysfunction, and a wide variety of neurologic symptoms including change in mental status, stroke, seizures, and coma. Once almost uniformly fatal, treatment has markedly improved mortality. Initial therapy includes steroids and antiplatelet agents. The use of gamma-globulin infusion, vincristine, plasma exchange (plasmapheresis), and surgical splenectomy in resistant cases has further reduced the mortality rate. Platelet transfusion should be avoided because platelets may cause additional thrombi in the microcirculation, though it may be necessary in cases of life-threatening hemorrhage. Most cases of TTP are idiopathic, but it has been associated with E. coli 0157:H7 infection and medications such as quinine. Clinically, TTP must be differentiated from other causes of MAHA such as: disseminated intravascular coagulation (DIC), the hemolytic uremic syndrome (HUS), and HELLP syndrome.