Red herrings and rocky mountains: a case of unsuspected rocky mountain spotted fever in a critically ill patient

Abstract

Rocky Mountain Spotted Fever is a tick-borne illness caused by Rickettsia rickettsii that can rapidly progress to irreversible fatal outcomes, especially with delayed treatment. Diagnosis of this disease can be difficult given its initial non-specific presentation that can easily be mistaken for other community-acquired illnesses or non-infectious etiology. This case was also confounded by a red herring associated with the limitation of unknown diagnostic tests. Here we report a 62-year-old male who presented for three days of altered mentation, fever, and significantly elevated blood alcohol level (0.372 WT/VOL). Relevant findings on initial ED evaluation include leukocytosis (11.5 K/uL), lactic acidosis (3.2 mmol/L), AKI (Cr 3.04 mg/dL, from baseline 0.8 mg/dL), transaminitis (AST 145 U/L, ALT 57 U/L). Patient was admitted to intensive critical care, started on phenobarbital taper for alcohol withdrawal, and concomitantly treated with vancomycin and cefepime for broad sepsis coverage. An initial tick-borne infection panel resulted on hospital day (HD) 1 and was negative, and an atypical infection was believed to be ruled out. Over the next three days, the patient rapidly deteriorated into acute respiratory failure requiring rapid sequence intubation, acute renal failure started on renal replacement therapy, septic shock, thrombocytopenia, and acute deep vein thrombosis. Patient was finally started on doxycycline on hospital day 3 after an unidentified rickettsial panel yielded high titer immunoglobulin M and G for RMSF. Patient fortunately improved with extended doxycycline treatment and was able to be discharged, though now with persistent peripheral neuropathy, ataxia, and short-term memory deficits. This case serves as a reminder of the high mortality outcome for delayed RMSF treatment. In addition, while clinicians strive to maintain broad differential, it is just as important to develop a structured approach to ensure accurate interpretation of clinical data and familiarity with the limitations of various diagnostic tests.