A50-01 Tick Triggered Chaos: Anaplasmosis Presenting as Acute Respiratory Distress Syndrome and Alveolar Hemorrhage

Abstract Introduction Human granulocytic anaplasmosis (HGA) is a tick-borne illness caused by Anaplasma phagocytophilum.i Although typically a self-limited febrile illness, it can present with severe complications including acute respiratory distress syndrome (ARDS), encephalopathy, and multiorgan failure.ii We describe a rare case of HGA manifesting with ARDS and diffuse alveolar hemorrhage (DAH), highlighting the diagnostic challenges and importance of early antimicrobial therapy. Case Description A 64-year-old man with coronary artery disease and heart failure presented with malaise, subjective fevers, and abdominal pain. He was febrile, hypotensive, and hypoxic on arrival. Laboratory studies showed hyponatremia, thrombocytopenia, transaminitis, and acute kidney injury. Imaging demonstrated interstitial pulmonary edema and pancreatitis. Despite broad-spectrum antibiotics and fluid resuscitation, he developed progressive shock, encephalopathy, and respiratory failure requiring intubation and transfer to a tertiary medical ICU. Bronchoscopy revealed diffuse alveolar hemorrhage. Given concern for vasculitis, he received pulse-dose corticosteroids and plasma exchange. Autoimmune testing was negative. Anaplasma phagocytophilum serology returned positive, and doxycycline was initiated. His course was complicated by acute renal failure requiring renal replacement therapy and ventilator dependence necessitating tracheostomy. Gradual improvement followed initiation of doxycycline, with resolution of fevers, stabilization of renal function, and recovery of mental status. He was ultimately discharged to a rehabilitation facility for ventilator weaning. Discussion This case illustrates a fulminant presentation of HGA with ARDS and DAH, a combination rarely reported. The nonspecific prodrome and initial laboratory findings mimicked abdominal sepsis and vasculitis, delaying diagnosis. Severe manifestations such as ARDS and multiorgan failure are thought to result from an exaggerated inflammatory response triggered by Anaplasma infection of neutrophils.iiiiv Early recognition and prompt empiric doxycycline therapy are crucial, as delayed treatment can lead to rapid deterioration. Clinicians should maintain high suspicion for HGA in endemic regions during tick season when encountering patients with febrile illness and unexplained cytopenias or respiratory failure. This case expands the clinical spectrum of anaplasmosis and underscores its potential to mimic vasculitic processes with life-threatening pulmonary involvement. References i Bakken and Dumler, “Human Granulocytic Anaplasmosis.” ii MacQueen and Centellas, “Human Granulocytic Anaplasmosis.” iii Malik et al., “Severe Fatal ARDS Due to Untreated Human Granulocytic Anaplasmosis in a 67-Year-Old Man.” iv Dumler et al., “Anaplasma Phagocytophilum Activates NF-κB Signaling via Redundant Pathways.” This abstract is funded by: None