ADAMTS13 inhibitor and anti-ADAMTS13 IgG/IgM/IgA in a cohort of 35 patients with acute TMA. Each TMA patient is represented by a symbol. Black circles are for patients with IgG, gray circles for patients with IgA, white circles for patients with IgM, and black triangles for patients with no detectable IgG/IgM/IgA. IgG/IgM/IgA titers are expressed as the reciprocal of patient plasma dilution. An isolated IgG was detected in 26 patients, the combination IgG and IgM in 1 patient, the combination IgG and IgA in 4 patients, and the combination of IgG, IgM, and IgA in 2 patients (indicated by numbers referring to patients in Table 1). Two patients had neither an IgG, IgM, nor IgA. ADAMTS13 inhibitors are expressed as semiquantitative titers: 4 patients had no detectable ADAMTS13 inhibitor, 14 patients a low titer, 5 patients a medium titer, and 12 patients a high titer. Twenty-nine patients had both an ADAMTS13 inhibitor and an anti-ADAMTS13 IgG/IgM/IgA (inhibitory anti-ADAMTS13 antibodies), and 4 patients had an anti-ADAMTS13 IgG/IgA with no ADAMTS13 inhibitor (noninhibitory anti-ADAMTS13 antibodies). Two patients had no IgG/IgM/IgA but an ADAMTS13 inhibitor.