Case Presentation: A 79-year-old male with a past medical history of coronary artery disease presented to the emergency department with a 1-week history of generalized weakness, fever, and chills. He reported associated generalized myalgia involving his chest, abdomen, and neck, as well as headache, productive cough, and diarrhea. There was no associated skin rash.On presentation, the patient was febrile with a temperature of 38.2°C but was otherwise hemodynamically stable. Physical examination revealed no skin rash. Laboratory workup was notable for thrombocytopenia with a platelet count of 20 x 10⁹/L, transaminitis with aspartate transaminase (AST) of 172 IU/L and alanine transaminase (ALT) of 75 IU/L, acute renal failure with a creatinine level of 2.25 mg/dL (baseline creatinine 1 mg/dL), azotemia with a BUN of 51 mg/dL, an elevated C-reactive protein (CRP) of 196 mg/L, and ferritin >7500 ng/mL. There was no leukocytosis or leukopenia.A computed tomography (CT) scan of the chest, abdomen, and pelvis revealed no findings suggestive of an infectious source. The patient subsequently became encephalopathic, prompting a lumbar puncture. Cerebrospinal fluid analysis and cultures were negative for infection. A respiratory viral panel returned positive for Human metapneumovirus.A tick-borne disease panel later confirmed Rocky Mountain Spotted Fever with an IgG titer of 1:256. The patient was started on doxycycline, resulting in clinical improvement, including resolution of fever and encephalopathy, and gradual improvement in thrombocytopenia, inflammatory markers, transaminitis, and renal function.
Discussion: This case underscores the diagnostic challenge of atypical RMSF presentations, particularly in patients without a rash, a hallmark feature often relied upon for early diagnosis. In such cases, thrombocytopenia, transaminitis, renal dysfunction, and elevated inflammatory markers should prompt consideration of RMSF, particularly in endemic regions or in the context of tick exposure. A broad differential diagnosis, including other tick-borne illnesses and systemic inflammatory conditions, is crucial. Encephalopathy and multiorgan involvement highlight the potential severity of untreated RMSF. Serologic testing plays a critical role in confirming the diagnosis, but empirical treatment with doxycycline should not be delayed when clinical suspicion is high.
Conclusions: Atypical RMSF presentations without rash require heightened clinical awareness to prevent diagnostic delays. Clinicians should consider RMSF in febrile patients with systemic inflammatory findings and multiorgan dysfunction. Early treatment with doxycycline remains the cornerstone of management and is essential to improving outcomes and reducing mortality.