Pyoderma gangrenosum as a manifestation of multisystem autoimmunity in a patient with giant cell arteritis, optic neuritis and rheumatoid arthritis.

Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis typically associated with autoimmune disease; however, its coexistence with giant cell arteritis (GCA) and optic neuritis is exceedingly uncommon and rarely reported. We describe a woman in her early 70s with rheumatoid arthritis and recently diagnosed GCA who developed painful breast ulcers while on tapering systemic corticosteroids for GCA, shortly after a herpes zoster infection. The ulcers showed classic PG morphology and fulfilled Delphi diagnostic criteria. She had preceding MRI-confirmed bilateral optic neuritis followed by bilateral temporal arteritis. Intralesional corticosteroid therapy resulted in complete ulcer healing within 1 month. This case highlights an unusual constellation of PG, GCA, rheumatoid arthritis and optic neuritis, with herpes zoster as a potential pathergic trigger. It emphasises the importance of considering PG in atypical ulceration occurring in patients with multisystem autoimmunity, even when lesions develop despite ongoing low-dose systemic corticosteroid therapy.