Complement-Mediated Thrombotic Microangiopathy in a Patient With Antiphospholipid Syndrome and Anti-glomerular Basement Membrane Antibodies.

Thrombotic microangiopathy (TMA) is a range of diseases characterized by thrombocytopenia, microangiopathic hemolytic anemia, and organ injury. Complement-mediated TMA is a rare, life-threatening subtype of TMA that occurs due to the uncontrolled activation of the alternative complement pathway in the absence of normal regulation, often resulting from deficiencies of various regulatory proteins. Anti-glomerular basement membrane (anti-GBM) disease, previously known as Goodpasture syndrome, is a life-threatening form of vasculitis in which immunoglobulin G autoantibodies bind to the alpha-3 chain of type IV collagen in alveolar and glomerular basement membranes. We present the case of a patient with a history of antiphospholipid syndrome who was diagnosed with complement-mediated TMA during hospital admission for elevated anti-GBM antibody titers discovered during an outpatient evaluation for elevated creatinine levels. Upon admission, treatment was started for presumed anti-GBM disease, including high-dose intravenous methylprednisolone injections and multiple plasmapheresis sessions. However, renal biopsy results showed no evidence of anti-GBM disease, but rather evidence of TMA. Subsequent laboratory studies revealed decreased complement levels, suggestive of a diagnosis of complement-mediated TMA. The patient was started on rituximab and eculizumab infusions, and she was discharged in stable condition after a 15-day hospitalization with outpatient appointments scheduled for genetic testing and further infusions. This case illustrates the importance of recognizing the key clinical and diagnostic features of complement-mediated TMA to promptly initiate appropriate therapy.