[Digital purpura revealing septicaemical rat-bite fever]

Infection with Streptobacillus moniliformis is an uncommon illness which can lead to death if untreated. We report the case in which initially cutaneous signs permitted diagnosis and further identification of the organism.

A 42 year-old woman presented with a three-day history of acrally distributed purpuric macules on her fingers. Two days later, she was admitted for arthritis of the knees and wrists. There were two large pustules on the left elbow and the right knee. Laboratory studies showed inflammatory changes. The diagnosis of streptobacillary rat-bite fever was made after isolation of Gram-negative bacilli from a blood-culture and from cutaneous lesions. Finally identification of the organism was made by molecular biology analysis. The patient received intravenous ofloxacin and imipenem with complete resolution of arthritis and the cutaneous lesions.

Streptobacillary rat-bite fever is a systemic infectious disease. It is caused by Streptobacillus moniliformis, organism found in the oropharyngeal flora of small rodents, especially rats. The illness is uncommon in urban settings. It starts by fever, followed by arthritis and rash. Septicaemical rat-bite fever may start only with cutaneous involvement such as acral purpura, like in our case. This clinical manifestation must be recognized by the dermatologist, because the illness can lead to death if untreated.