Renal-Limited Thrombotic Microangiopathy Presenting as Acute on Chronic Kidney Failure in the Absence of Schistocytosis.

We report a rare presentation of renal-limited thrombotic microangiopathy (TMA). TMA is a clinicopathologic syndrome resulting from endothelial injury and activation of the coagulation and platelet pathways, leading to the formation of platelet-rich microthrombi within small vessels. This loss of blood flow due to the thrombi can result in tissue ischemia and end-organ injury. Systemic TMA classically manifests with the triad of microangiopathic hemolytic anemia (MAHA), thrombocytopenia, and organ dysfunction. However, TMA may be limited predominantly to the kidneys, resulting in acute or progressive renal dysfunction without the classic systemic hematologic manifestations, making diagnosis challenging. In this case, a 46-year-old woman with stage three chronic kidney disease (CKD) and untreated hypertension (HTN) presented with acute renal failure and chest pain. The initial differential diagnoses included systemic lupus erythematosus, glomerular disease, vasculitis, and TMA. An extensive diagnostic evaluation including peripheral blood smear, autoimmune serologies, and skin biopsy was largely unrevealing until kidney biopsy demonstrated findings consistent with TMA. She was ultimately diagnosed with renal-limited TMA and discharged with plans to initiate outpatient peritoneal dialysis for her newly progressed stage five CKD. This case highlights the diagnostic challenge of renal-limited TMA and emphasizes the importance of considering TMA in patients with otherwise unexplained acute or progressive renal dysfunction, even in the absence of the classic hematologic findings.