COVID AnTicks: Not All Infiltrates Are COVID Related

Introduction: Anaplasma phagocytophilum causes human granulocytic anaplasmosis (HGA). We present a case of ARDS due to HGA, highlighting the importance of maintaining a broad differential and thorough history taking even in the midst of a pandemic. Case: A 43 year-old man with a history of alcohol and tobacco use presented in late November 2020 in the midst of a regional COVID-19 surge with two weeks of progressive shortness of breath, chest pain, fevers, and altered mental status. Admission labs were notable for hepatocellular injury, thrombocytopenia, leukopenia with absolute lymphopenia, and elevated creatinine. The patient's hypoxemia progressed to the point of requiring mechanical ventilation despite broad spectrum antibiotics. SARS-CoV-2 PCR x3, blood, viral, and fungal cultures were negative. Patient's PaO2/FiO2 ratio of <200, extensive bilateral infiltrates, and low suspicion for heart failure was consistent with ARDS (Figure). Given continued hypoxia, the patient underwent the prone positioning protocol. A peripheral smear was obtained for thrombocytopenia/leukopenia and demonstrated inclusions within the neutrophils consistent with Anaplasma. Upon further history taking, the spouse confirmed that the patient had recently found several ticks on his body after returning from a hunting trip in northern Minnesota. Anaplasma was confirmed with PCR testing. The rarity of ARDS due to anaplasmosis limits insight into therapeutic options aside from antibiotics. However, in addition to receiving doxycycline, the patient was started on dexamethasone, which has demonstrated possible symptomatic benefit through small case studies. The dosage of Dexamethasone administered ranged from 4-20 mg, totaling 5 doses. The patient improved and was discharged home. Discussion: Human granulocytic anaplasmosis is caused by Anaplasma phagocytophilum. Ticks are the main vectors for this zoonotic disease, specifically the Ixodes tick. Like other tick-borne infections, it presents most commonly as a febrile illness. Our patient had several classic manifestations including leukopenia, thrombocytopenia, and elevated transaminases. Pulmonary symptoms are infrequently described aside from some reports of interstitial pneumonia and, rarely, ARDS. Doxycycline is the gold standard treatment for HGA. A few case reports have demonstrated clinical improvement with the addition of steroids when ARDS was present. Our patient saw improvement with the combination of corticosteroids, doxycycline, and ARDS evidencebased practices (i.e. pronation and low tidal volume ventilation). Similar management should be considered in other patients presenting with severe ARDS caused by HGA. Finally, although an atypical season for ticks, this case highlights the importance of a thorough social history and broad differentials, especially in patients presenting with severe illness.