A 45-year-old male patient was admitted to a local hospital with a history of high fever and myalgia, predominantly in the lower limbs and lumbar region for 1 week. After 11 days of the initial symptoms, the patient presented with petechiae and melena, followed by headache, reduced consciousness, and increasing jaundice within the past 48 hours. On admission, the patient presented with fever (axillary temperature, 38.2 C), tachycardia (heart rate, 106 beats/min), a blood pressure of 160 mmHg systolic and 90 mmHg diastolic, and a respiratory rate of 20/min. Laboratory data on admission are summarized in Table 1. In a 24-hour interval, clinical conditions deteriorated and the patient was placed on artificial ventilation. At this point a presumptive diagnosis of TMA was established based on the abrupt onset of thrombocytopenia, microangiopathic hemolytic anemia, elevated lactate dehydrogenase (LDH), neurologic abnormalities, and renal failure. Infusion of fresh-frozen plasma was introduced (10 mL/kg/day), until transference to a reference hospital was possible. Two days later, the patient was transferred to the intensive care unit of a university hospital where plasma exchange was available. On this admission the laboratory data (Table 1) showed an elevated level of LDH (2662 IU/L; normal range, <480 IU/L), low PLT count (11.0 x 109/L), a hemoglobin (Hb) level of 7.1 g/dL, a negative direct antiglobulin test, and negative RBC antibodies. Serum bilirubin (total and direct) was slightly elevated (1.83 and 0.77 g/dL; normal ranges, <1.0 and 0.7 g/dL, respectively), elevated serum creatinine (1.97 mg/dL), slightly prolonged prothrombin time (17 sec; control, 12.8 sec), and normal activated partial thromboplastin time (ratio, 1.01). Peripheral blood smear showed 5 to 10 schistocytes per high-power field and 14% erythroblasts of total RBCs. Flow cytometry assay was also performed to identify autoantibodies against PLTs, but the results were negative for both IgG and IgM. Other tests for antibodies against glycoprotein (GP) IIb-IIIa (Gi5), GPIa-IIa (Gi9), and GPIb-IX (anti-CD42) were also negative.
The patient lived in an area where a dengue fever outbreak was occurring. In addition, he had a positive exposure to leptospirosis due to his occupation. Dengue serology tests were performed, including Dengue IgM capture enzyme-linked immunosorbent assay (PanBio, Queensland, Australia) and DV IgM- and IgG-specific tests (Dengue DuoCassette, PanBio), and all confirmed-positive IgM results, suggesting the acute dengue viral infection. Serologic tests for leptospirosis, hantavirus, and Brazilian spotted fever, performed in a reference public health laboratory, were negative as the differential diagnosis imposed by the epidemic of DV infection in the icterus-hemorrhagic fever syndrome (as shown by a positive tourniquet test) plus thrombocytopenia.
We sought to determine whether TMA rather than icterus-hemorrhagic fever syndrome was the main underlying mechanism of the patient clinical evolution. The activity of ADAMTS13 and presence of autoantibodies against ADAMTS13 was then evaluated. The results obtained in blood samples collected at 2 weeks of the beginning of the fever showed that ADAMTS13 activity was below 5% of normal human plasma. Autoantibodies against ADAMTS13 were detected at a titer of 3 units/mL. Both ADAMTS13 activity and autoantibody inhibitors were determined by two different assays (FRETS-VWF73 and collagen-binding assay) as previously described. The anti-ADAMTS13 IgG bound specifically to both full-length ADAMTS13 and the variant deleted after the seventh TSP1 repeat (delCUB-CUB domain presents peptide sequences of complement subcomponents C1r/C1s; embryonic sea urchin protein EGF; and bone morphogenic protein-1), which were expressed in HEK293 cells. The antibody-antigen complexes were determined by immunoprecipitation, followed by Western blot with anti-V5 that recognizes the C-terminal V5-His tag (Fig. 1). The amount of ADAMTS13 or variant that could be pulled down with IgG from this DV-infected patient was similar to that with IgG from a TTP patient with acquired idiopathic TTP caused by known anti-ADAMTS13 IgG. Taken together, the clinical manifestations, response to the treatment, and the detection of anti-ADAMTS13 IgG autoantibody formation all suggest the diagnosis of TMA (probably TTP) concomitant to DV infection.
We opted for a therapy for TTP by plasma exchange therapy (1.0 plasma volume, daily) due to severity of the case, initiated before laboratorial results confirming DV infection. The time course of clinical and laboratorial findings showed evidence of temporal clinical and laboratorial improvements (Fig. 2). After 11 plasma exchanges, the PLT count recovered to values of 123 x 109/L and LDH decreased to 660 IU/L when plasma exchange was discontinued. At 4-month follow-up, the patient exhibited a normal PLT count and a normal level of serum LDH. Plasma ADAMTS13 activity returned to 100% of normal human plasma and no anti-ADAMTS13 inhibitor was detected at this time. No recurrence of TMA was observed after 2-year follow-up.