Bywaters' lesions are characteristic cutaneous manifestations of patients with rheumatoid arthritis (RA). They include nail-fold thrombosis and reddish-brown-purpuric papules on a few distal digits (especially the digital pulp).

These lesions correspond to small painless infarcts of the nail fold due to mild necrotizing vasculitis. Typically these lesions are not associated with systemic signs of  vasculitis.

They start as periungual swelling followed by skin infarcts and necrosis that leave brown eschars which disappear within a few days leaving or not (usually) a scar in the nail fold and on the ends of the digits.
Histologically, there is a small vessels leukocytoclastic vasculitis.
These lesions were first described in 1949 by Eric George Lapthorne Bywaters, an English Professor of  Rheumatology, pioneer of a new management of children affected by juvenile chronic arthritis. He contributed in bringing the medical perception of rheumatology firmly into the orbit of general medicine. He counted 349 trainees over his period of service, “seeding” rheumatologists and rheumatology expertise throughout the world.

He was also a keen gardener and a member of the Royal Horticultural Society. In his Beaconsfield garden there stands a Platanus orientalis that he grew from a seed from the original plane tree under which Hippocrates is said to have taught.