Objective:To define phenotypic subgroups of thrombotic microangiopathy (TMA) by integrating clinicopathologic data to identify patterns suggestive of pathogenic features and etiologies.
Patients and Methods:We retrospectively analyzed 283 patients with biopsy-confirmed renal TMA between January 1, 2010, and December 31, 2020. Sixty-four clinicopathologic variables were applied in consensus clustering.
Results:Three distinct clusters were identified. Cluster 1 (n=78), predominantly women (n=50, 64%), was enriched for drug-induced (n=23, 29%), lupus-associated (n=9, 12%), and post-bone marrow transplant TMA (n=8, 10%). It showed wide immune-complex staining (IgM, C3, κ, and λ) and subendothelial deposits (n=16, 21%), suggestive of immune-associated injury. Cluster 2 (n=92) included the oldest patients (54±18 years) and was dominated by drug-induced TMA (n=21, 23%; one-third owing to vascular endothelial growth factor inhibitor bevacizumab) and monoclonal gammopathy-associated TMA (n=10, 11%). It showed marked endothelial damage (n=65, 71%) and mesangiolysis (n=66, 72%) with little immune staining, suggesting a toxic-related injury. Cluster 3 (n=113) exhibited the worst outcomes, with 80% (24/30) progressing to renal failure, compared with 31% (12/39) in cluster 1 and 34% (16/47) in cluster 2. This cluster was characterized by the youngest age (45±14 years), mostly males (n=67, 59%), severe hypertension (n=75, 66%), and low estimated glomerular filtration rate (10 mL/min/1.73 m2; interquartile range, 7-16). Biopsies showed acute vascular lesions-wrinkling of capillary tufts (n=74, 65%), fibrin thrombi (n=67, 59%), mucoid intimal edema (n=85, 75%), and onion-skin-type hyperplasia (n=55, 49%)-with minimal deposits (n=1, 0.9%), suggesting a severe vascular lesion process.
Conclusion:Integrative clustering of clinical and histologic data in TMA identified 3 clinicopathologic phenotypes that may suggest underlying immune-, toxic-, or severe vascular lesion-related drivers. These findings support data-driven classification that may help prioritize diagnostic and therapeutic considerations.