Case Presentation: A 72 year old woman with osteoarthritis presented to with a 3-day history of fever and chills. A few days prior to presentation, she had received a glucocorticoid injection for left knee pain. Upon assessment of her initial vitals, heart rate was 122 bpm, blood pressure was 147/77 mmHg, respiratory rate was 22, temperature was 38.1C, and she was saturating at 94 % on room air. Physical exam revealed a normal exam except for bilateral conjunctival injection. Laboratory results revealed a white cell count of 7 K/µL, hemoglobin of 13.7 g/dL, low platelet count of 41 K/µL with an unknown baseline, low sodium of 127 mmol/L, high creatinine of 1.73 mg/dl, high lactate of 3.4 mmol/L, creatinine phosphokinase (CPK) of 1873 unit/L which increased to 6811 unit/L the next day, concerning for rhabdomyolysis. Patient also had elevated liver function tests- ALT of 47 unit/L, AST of 99 unit/L, and total bilirubin of 1.3 mg/dL. Urinalysis revealed 5-9/hpf RBCs. She recalled a remote history of tick bite two months prior. With a high suspicion for a tick-borne illness, she was started on doxycycline as well as broad spectrum antibiotics for possible septic arthritis. Various serologic testing including Anaplasma, Babesia, Ehrlichia IgG and IgM antibodies were negative. Leptospira IgM, which was ordered since she has bilateral conjunctival injection, was also negative. Her broad-spectrum antibiotics were discontinued once septic arthritis was ruled out. She continued on doxycycline and received minimal intravenous fluids for rhabdomyolysis. Her peripheral smear was negative for blood parasites, extraerythrocytic and intraleukocytic inclusion organisms. A malaria smear was performed to rule out Babesia, which can co-infect with Anaplasmosis, and was negative. She responded well to doxycycline, her rhabdomyolysis and acute kidney injury resolved, and her sodium and platelet count were normal on the day of discharge. She improved symptomatically and was discharged home. PCR was positive for Anaplasma and negative for Ehlrichia, thereby confirming the diagnosis.
Discussion: The exact etiology of rhabdomyolysis and subsequent renal failure associated with Anaplasma infection is unknown, although elevation of cytokine induced skeletal muscle damage has been proposed. Treatment should be initiated promptly without waiting for laboratory diagnosis such as IgG/IgM antibodies, peripheral smear testing. PCR is the test of choice and should be used to confirm serology if they are positive.
Conclusions: Rhabdomyolysis and subsequent renal failure is a rare complication of anaplasmosis. Checking CPK is warranted in any patient who presents with this infection.