Patients with acute immune-mediated thrombotic thrombocytopenic purpura (iTTP) present with marked endothelium-mediated microvascular hyporeactivity that could contribute to organ injury pathophysiology, according to research published in Critical Care.

Researchers conducted a prospective observational study in adult patients with iTTP to evaluate endothelial-mediated vasoreactivity in patients with iTTP at admission and its changes after plasma exchange therapy.

The team assessed skin microvascular blood flow and endothelium-mediated vasoreactivity using laser Doppler flowmetry and acetylcholine (Ach) iontophoresis in the forearms of patients with iTTP at admission and after plasma exchange therapy. They used data from a previously published cohort of patients with diabetes that was recorded after correction of ketoacidosis as a control group.

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The study included 18 patients with confirmed iTTP (mean age, 43 years; 72% women and 28% men) and 34 control patients (mean age, 44 years; 32% women and 68% men). Among the patients with iTTP, 55% had neurological abnormalities, 50% cardiac issues, and 27.8% an acute kidney injury at admission.

At admission, patients in the iTTP group showed decreased microvascular blood flow compared with those in the control group (mean baseline perfusion index, 5.97 vs 10.1 PU; P =.03). Patients in the iTTP group also had impaired endothelial-mediated microvascular reactivity (response to Ach iontophoresis peak perfusion index, 31.9 vs 67.7 PU; P =.001) and a lower area under the curve (AUC perfusion, 9627 vs 16 475 PU; P =.03) compared with those in the control group.

Patients with iTTP underwent 2 sessions of plasma exchange therapy. The researchers report improved global microvascular blood flow (mean baseline perfusion index, 5.97 vs 11.38 PU; P =.027) and microvascular reactivity (AUC perfusion, 9627 vs 16 558 PU; P =.007) from baseline to after the first session and continued improvement in microvascular reactivity after the second session (16 558 vs 26 431 PU; P =.04).

“We showed that the microvascular reactivity of [patients with iTTP] is impaired and, therefore, could participate in organ injury besides the thrombotic process,” the researchers said in their report. “Given that patients with cardiovascular risk factors are susceptible to a lower microvascular reactivity; difference[s] between healthy [individuals] and [patients with iTTP] could be even more important than differences between [patients with diabetes] and [those with iTTP].”

Limitations of the study included the single-center design, a limited number of patients, receipt of additional treatment by nearly all patients with iTTP, use of data from patients with diabetes rather than individuals without chronic illness as the control, an inability to evaluate the endothelium of key organs with the device used in the study, and the lack of exploration of endothelium-independent vasodilation.


Joffre J, Raia L, Urbina T, et al. Reversible skin microvascular hyporeactivity in patients with immune-mediated thrombocytopenic thrombotic purpura. Crit Care. 2023;27(1):116. doi:10.1186/s13054-023-04405-w