A Rare Case of Concurrent New-Onset Microscopic Polyangiitis and Thrombotic Thrombocytopenic Purpura in a 77-Year-Old Woman

Introduction:

Microscopic polyangiits (MPA) is a rare ANCA-associated necrotizing vasculitis that affects the small vessels, often involving the lung or kidney. When presenting with diffuse alveolar hemorrhage, this disease warrants emergent treatment, often with plasma exchange. Here, we present a rare case of a patient presenting with alveolar hemorrhage in the setting of MPA and concurrent thrombotic thrombocytopenic purpura (TTP) with an extremely reduced ADAMTS13 activity.

Case Report:

A 77 y/o woman with HTN and PUD presented to outside facility with new onset anemia (Hb 6.3 g/dL). Positive Coombs test gave her a tentative diagnosis of hemolytic anemia, and she was transfused 2 U RBCs. Ten days later, she presented to our hospital with respiratory distress. Hb remained stable at 10.7 but had leukocytosis with WBC 22,000 with left shift, platelets 439. Vitals not consistent with sepsis though saturating 70-80% on room air. In the ED, she developed frank hemoptysis and was emergently intubated. CTA chest was negative for pulmonary embolus but demonstrated diffuse ground-glass opacities. COVID test negative. Bronchoscopy was consistent with diffuse alveolar hemorrhage (DAH), and she received tranexamic acid, crystalloids, 1 U RBCs. Suspicious for underlying vasculitic process, she was given pulse dose IV steroids (1 g methylprednisolone daily) and started plasma exchange. Creatinine on presentation was elevated at 1.77 but she continued to have adequate urine output and appropriate volume status. Her hospital course was marked by progressive thrombocytopenia with schistocytes appreciated on peripheral smear. ADAMTS13 activity <5% with inhibitor detected, consistent with TTP. Vasculitic workup revealed positive myeloperoxidase antibodies and p-ANCA consistent with MPA. Other rheumatologic workup ANA positive 1:640 and positive IgM cardiolipin antibodies; she had no personal autoimmune history but some family autoimmune disease including one daughter with systemic lupus erythematosus and another relative with Guillian-Barre. She remained intubated for 4 days and post-extubation experienced some short-lived ICU delirium but after made a remarkable recovery. She completed 12 total sessions of of plasma exchange and 3 of 4 planned doses of rituximab, to continue on oral steroids outpatient and prophylactic TMP-SMX. She was discharged to rehab facility on hospital day 20.

Discussion:

With diffuse alveolar hemorrhage on presentation, initial differential remained broad including delayed presentation of transfusion-related lung injury (TRALI) given recent history of transfusion. She had recently started hydralazine outpatient. Along with positive ANA, this could suggest drug-induced lupus. However, histone antibodies were negative, but results may have been compromised by steroids and plasma exchange. Both MPA and TTP can be deadly but are managed with similar treatment. Luckily, our patient was rapidly initiated on plasma exchange following hospitalization. Although further workup including ADAMTS13 and vasculitis labs were pending at the time, it is important to not delay treatment while awaiting results. Cased of concurrent TTP and ANCA-associated vasculitis have been described in the literature, but the full relationship between these two entities remains unclear. TTP may develop after starting glucocorticoids in the setting of ANCA vasculitis, so close monitoring is recommended.