Rat bite erosions (gout)

Last revised by Dr Daniel J Bell on 06 Jan 2022

Rat (or mouse) bite erosions, also known as Martel sign or G sign, are seen in gout and refer to punched out erosions with sclerotic and overhanging margins.

History and etymology

This characteristic presence of the overhanging margin associated with the erosion in gout was first described by William Martel (1927–2014), an American radiologist, in 1968 3-5.

Differential diagnosis

Punched out erosions are seen in several chronic erosive joint diseases, e.g. rheumatoid arthritis. However it is the presence of the overhanging margin displaced away from the cortex of the originating bone which is distinctive for gout and is only occasionally seen in other conditions such as rheumatoid arthritis 6.

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Cases and figures

  • Case 1: Gout arthropathy
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  • Case 2
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  • Case 3
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  • Case 4
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