Gene variants. Gene variants identified after a rigorous filtering process are shown as a heat map. Each vertical column marks 14 genes that were included after data filtering, some with multiple variants (CFP, C4BPA, and CD59 were excluded from the 17-gene panel because of the absence of the variants detected). Numerical list 1-42 correlates with the specific gene variant listed in supplemental Table 2. Each horizontal line represents 1 study patient (HSCT recipient). Heterozygous variants are shown in blue and homozygous variants are shown in red. (A) Gene variants identified in all 77 HSCT recipients: 26 (34%) of 77 of patients had at least 1 gene variant detected. (B) A majority of gene variants are present in HSCT recipients with TMA (top panel), whereas few variants are seen in those without TMA (bottom panel). The median number of gene variants (of known or uncertain clinical significance) seen in recipients with TMA was 1 (range, 0-7) and 0 (range, 0-2) in those without TMA (P < .0001). (C) Gene variant distribution by race and TMA. All 10 nonwhites (100%) with TMA had at least 1 variant detected, whereas 12 (50%) of 24 of whites had variants identified. Three or more (range, 3-7) variants were identified only in nonwhite recipients with TMA (n = 7); 5 (71%) of these 7 patients died of severe TMA, indicating the effect of race and complement gene variants on TMA phenotype. CFD variant c.357+16C>A (number 32) was identified exclusively in African American HSCT recipients. Of 12 whites with TMA who had gene variants identified, only 3 had 2 variants and the other 9 had a single variant detected. Only 3 (7.7%) of 39 nonwhites without TMA had a single variant detected.