https://www.ncbi.nlm.nih.gov/pubmed/32087981

2020 Feb 19. pii: S0151-9638(20)30077-6. doi: 10.1016/j.annder.2020.01.016. [Epub ahead of print]

[Multiple erythema annulare centrifugum associated with knee monoarthritis revealing Capnocytophagacanimorsus infection].

[Article in French]

Abstract

INTRODUCTION:

Capnocytophagacanimorsus (C. canimorsus), a commensal Gram-negative bacillus found in the oral cavity of dogs and cats, is pathogenic for humans, with the most common clinical manifestations being septicemia, meningitis and endocarditis. Herein we report a case of CC bacteremia manifesting as multiple plaques of erythema annulare centrifugum associated with monoarthritis of the knee.

PATIENTS AND METHODS:

A 66-year-old man consulted for a skin rash and monoarthritis of the right knee with fever following an insect bite on his right hallux. Cutaneous examination revealed numerous erythematous annular plaques on the trunk and limbs with centrifugal extension. Analysis of synovial fluid from the right knee showed an inflammatory liquid with a sterile bacteriological culture and PCR was negative for Borrelia. C. canimorsus bacteria were isolated from blood cultures. 16S RNA PCR performed on the synovial fluid was positive for the same organism.

The patient’s history revealed that his hallux wound had been licked by his dog.

DISCUSSION:

C. canimorsus most frequently affects immunosuppressed subjects. Cutaneous signs are seen in half of all cases, most frequently presenting as cellulitis, pathological livedo or thrombotic purpura. We report herein a case of CC bacteremia in an immunocompetent patient manifesting as multiple plaques of erythema annulare centrifugum, an unusual sign, and monoarthritis of one knee.

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**Comment**

I post this because many patients have pets.  Here we see the result of a man with an insect bite on his big toe being licked by his dog.  He was in good health but developed a skin rash, fever, and arthritis in the knee joint.  

This demonstrates that many organisms can cause pain & arthritis.

For more on erythematous annular plaques:  

annular-erythema-03__WatermarkedWyJXYXRlcm1hcmtlZCJdhttps://creativecommons.org/licenses/by-nc-nd/3.0/nz/legalcode

What are the clinical features of erythema annulare centrifugum?

Erythema annulare centrifugum typically affects the thighs, buttocks, and upper arms. However, any location on the body can be affected.

Erythema annulare centrifugum usually starts as a small pink papule that gradually enlarges over several weeks to form annular plaqueswith central clearing. These plaques can vary in size from a few millimetres to a few centimetres in size. Annular lesions can be partial (arciform) and coalesce to form polycyclic (ringed), serpiginous (wavy), and gyrate (revolving) patterns.

Classically, the annular or arciform lesions have an advancing outer erythematous edge with a trailing (inner) scaly edge. The rash may be itchy.

How is erythema annulare centrifugum diagnosed?

Erythema annulare centrifugum can sometimes be diagnosed on clinical features alone if the characteristic trailing scale is present. The diagnosis can be confirmed by skin biopsy in which the typical features of superficial or deep erythema annulare centrifugum are noted: a dense perivascular lymphocytic infiltrate involving either the superficial or deep vascular plexus, which is known as a ‘coat-sleeve’ appearance. Secondary changes to the epidermis may include spongiosis (inflammation of intercellular oedema), parakeratosis (disturbance in the keratinisation process), and hyperkeratosis (thickening of the outer layer of the epidermis) [2].  https://www.dermnetnz.org/topics/erythema-annulare-centrifugum/