Rat-bite fever (RBF) is a rare systemic infectious disease caused by Streptobacillus moniliformis, Spirillum minus, or Streptobacillus notomytis. As the name implies, the disease is typically transmitted by a rat bite. RBF usually presents as a combination of fever, arthritis, and rash. Definitive diagnosis of RBF may prove difficult, as the responsible bacteria are not easily identified with standard testing. We describe a case of RBF in a 34-year-old female who presented with fever, chills, polyarthralgia, and skin rash following a rat bite. Initial vital signs were remarkable for fever and tachycardia. Physical examination revealed an erythematous vesicular and papular rash involving her extremities, buttocks, and oral mucosa. Blood cultures were negative. A skin biopsy revealed leukocytoclastic vasculitis and was negative for Gram stain. Further analysis using specialized immunohistochemistry and polymerase chain reaction (PCR) identified S. moniliformis. A diagnosis of RBF was made, and the patient was successfully treated with a two-week course of doxycycline.
Keywords: fever; leukocytoclastic vasculitis; rash; rat-bite fever; streptobacillus moniliformis.
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