Ticked Off: A Case of Disappearing Cell Lines.

Human granulocytic anaplasmosis (HGA) is transmitted by the black-legged tick and presents with fever, thrombocytopenia, leukocytopenia, and elevated transaminases. If left untreated, HGA can progress to hemophagocytic lymphohistiocytosis (HLH), which can be fatal. Here, we discuss a case of a woman diagnosed with anaplasmosis who was treated promptly. A 63-year-old female presented with a two-day history of fever and fatigue. She denied any history of hiking but confirmed an avid gardening hobby. She did not report any tick bites or rashes. Upon presentation, she was febrile but hemodynamically stable. Her laboratory results showed elevated liver function tests (LFTs) and bicytopenia, with a white blood cell count (WBC) of 0.77 k/mcL (normal = 4.4-11.3 k/mcL), an absolute neutrophil count (ANC) of 150/µL (normal = >500/µL), and a platelet count of 50 k/mcL (normal = 145-445 k/mcL). Her liver function tests (LFTs) were elevated, including alanine aminotransferase (ALT) of 75 U/L (normal = 0-40 U/L) and aspartate aminotransferase (AST) of 66 U/L (normal = 0-40 U/L). Her lab results had been normal one month prior during routine testing. She was tested for Lyme antibodies, antibodies, and anaplasmosis via a polymerase chain reaction (PCR) test. She was started on doxycycline, and within two days, her counts began to recover. Her Lyme antibody titers and antibody tests were negative, but she tested positive for antibodies, confirming anaplasmosis. She was discharged home, and on follow-up, her WBC had risen to 4.6 k/mcL (normal = 4.4-11.3 k/mcL), and platelets increased to 84 k/mcL (normal = 145-445 k/mcL). Human granulocytic anaplasmosis is a rickettsial disease that typically presents with symptoms such as fatigue, malaise, fever, thrombocytopenia, and leukopenia. It carries a small but significant risk of progressing to HLH if not treated early in its course. Human granulocytic anaplasmosis has a presentation similar to ehrlichiosis and is differentiated based on PCR testing for deoxyribonucleic acid (DNA); however, since treatment is the same for both diseases, patients are often started on doxycycline before confirmatory test results are available. Physicians working in tick-endemic areas must maintain a high suspicion for rickettsial illnesses, as these patients often present with vague symptoms and can be undiagnosed if not properly evaluated.