A woman in her twenties with headache, fever and a rash

Background: Fever in combination with a rash is a presentation regularly seen in medicine. The causes clinicians must consider include infections, medications, autoimmune diseases.

Case presentation: A previously healthy young woman presented with a 3 to 4 day history of fever, headache and a maculopapular rash that also affected her palms. She was in a stable condition and was admitted for observation and further investigations without initiating antibiotic treatment. During the next two days her condition improved spontaneously, and her symptoms were initially interpreted as a viral infection. On day 3, blood cultures taken on the day of admission came back positive for Streptobacillus moniliformis, the causative agent of rat-bite fever. A more detailed patient history was taken, and the patient reported that she had several pet rats and one of them had given her some superficial scratches a few days before she fell ill.

Interpretation: Rats and other rodents are often colonised by Streptobacillus moniliformis in their oropharynx. Many people keep such animals as pets, and it is important to be aware of this disease as a differential diagnosis when a patient presents with fever and rash. Untreated, the disease might have a fatal course and the treatment of choice, penicillin, is usually easily available.