Puccinia caricina

Sedges (Carex) are the primary hosts, bearing uredinia and telia.   The alternate host is a Ribes.

This is a complex of species without a clear consensus; some authors describe different species depending on the species of Carex affected, and Puccinia caricina  should be regarded as sensu lato.  

Unless identified by a recognised expert, a photo is required. If the photo doesn't show the key ID features then in the comments box describe the size and identifying characters you have observed.

Widespread and fairly frequent in Britain.

Not often recorded  in Leicestershire and Rutland, possibly due to the difficulty of identification.

This is not described as a gall-causer in Redfern & Shirley (2023) but is listed sensu lato as a gall-causer on other sources - e.g. see species page on the Bladmineerders website, where it is described as a complex of species.