Anaplasmosis: A Rare Case of Rhabdomyolysis and Interstitial Nephritis

Introduction: Human Granulocytic Anaplasmosis (HGA) is a tick-borne illness caused by the bacterium Anaplasmaphagocytophilum. Clinical manifestations of HGA include fever, malaise, but in severe cases can lead to neurologic dysfunction, liver dysfunction, and rarely, renal dysfunction. We present a case of anaplasmosis leading to acute kidney injury (AKI) requiring kidney replacement therapy. Kidney biopsy was suggestive of rhabdomyolysis with acute tubular injury and interstitial nephritis. Case Description: A 59-year-old man presented to the emergency department with altered mental status. One week prior, he had experienced fevers and malaise. Laboratory data was significant for a platelet count of 23 x109/L, mild transaminitis, and rhabdomyolysis (CPK 29,818 IU/L). Serum creatinine was 2.8 mg/dL, baseline unknown, and peaked at 9.8 mg/dL. Urinalysis showed large blood, large protein, 10 red blood cells per high power field, and muddy brown casts on sediment. Spot urine protein/creatinine ratio was 2.37 g/g . Serum polymerase chain reaction was positive for A. phagocytophilum. He was treated with doxycycline and his mental status improved. His renal function worsened and hemodialysis was initiated. A kidney biopsy showed interstitial inflammatory infiltrates and focal acute tubular injury with myoglobin positive casts (Figure 1). His renal function improved and hemodialysis was discontinued. He did not require corticosteroid therapy. Discussion: HGA is a tickborne illness whose incidence is increasing in certain locations. We present a rare case of HGA causing severe AKI requiring dialysis. This case is unique in that the kidney biopsy revealed both rhabdomyolysis with acute tubular injury and interstitial nephritis. AKI from HGA requires prompt diagnosis as antimicrobial therapy can lead to significant improvement in renal function. Nephrologists should consider HGA as a cause of AKI in tick endemic areas.Figure 1: 600x. Myoglobin cast, myoglobin immunoperoxidase stain