Rat bite fever mimicking ANCA-associated vasculitis

Abstract

Rat bite fever (RBF) is a rare infectious zoonotic disease caused by two bacterial species: the Gram-negative rod Streptobacillus moniliformis and the Gram-negative coiled rod Spirillum minus. The association between RBF and skin vasculitis and arthritis has been observed. The aim of this paper was to present a case of rat-bite fever with symptoms of skin vasculitis and arthritis, associated with high titers of ANCA antibodies and anti-endothelial cell antibodies suggestive of primary vasculitis. The patient was successfully treated with antibiotics and non-steroidal anti-inflammatory drugs, leading to significant improvement. Based on the presented case, we discuss the differential diagnosis of the signs and the role of infection in the induction of ANCA antibodies. We reviewed the English language literature for cases of RBF presenting with symptoms of vasculitis and/or antibody presence. A literature review was performed in PubMed and Google using the keywords "rat bite fever" AND "vasculitis", "systemic vasculitis", "ANCA", "antiendothelial antibodies". No cases of rat-bite fever with the presence of ANCA antibodies or AECA antibodies in its course have been described thus far. Rat bite fever is a rare disease with nonspecific symptoms. In its course, general weakness, intermittent fever, leukocytoclastic vasculitis, and arthritis are reported. To our knowledge, this is the first reported case of ANCA positivity associated with RBF.

Keywords: ANCA-associated vasculitis; Arthritis; Fever; Purpura; Rat bite fever; Streptobacillus moniliformis.

Fig. 1

Purpuric lesions present on the feet and legs below the knee

Fig. 2

Synovial hypertrophy and joint effusion revealed in ultrasonography of the radiocarpal joint and intercarpal joint on the palmar side

Fig. 3

Increased second-degree synovial blood flow revealed in ultrasonography of the radiocarpal joint and intercarpal joint on the palmar side

Fig. 4

Thickening of tenosynovium, effusion, and synovial hypertrophy revealed in ultrasonography of the left musculus extensor digitorum longus tendon in long axis projection

Fig. 5

Increased blood flow within the tenosynovium revealed in ultrasonography of the left ankle joint

Fig. 6

Flowchart presenting the results of the literature review