Human Granulocytic Anaplasmosis presenting as Subacute Abdominal Pain and Hyponatremia

Human Granulocytic Anaplasmosis (HGA) is an acute febrile tick-borne illness caused by the organism Anaplasma phagocytophilum. Patients often present with fever and a flu-like symptoms following a tick bite. In this case, the patient presented with subacute abdominal pain and severe hyponatremia consistent with SIADH. The patient was started on appropriate empiric antibiotics given the patient’s tick exposure. Blood smear confirmed findings consistent with HGA and the patient continued antibiotic treatment with resolution of his symptoms. This case is unique in that the patient presented with severe hyponatremia that improved with treatment of the HGA. He also had subacute abdominal pain which is also a rare presentation of HGA. Our hope is that our case highlights the value of empiric treatment with appropriate monitoring to prevent downstream, severe sequelae from undiagnosed HGA. In the setting of climate change, increased duration of Ixodes spp. tick life cycles with emerging regional distribution of the ticks, coinfections with Borrelia burgdorferi and increased incidence of HGA in the last two decades, it is important to recognize this entity.