Sustained response to rituximab in an ANCA-negative necrotizing vasculitis with initial detection of Corynebacterium...

In this case, we present a patient with rapidly progressive unilateral destructive orbital and midface inflammation. Initial detection of Corynebacterium kroppenstedtii was followed by a consistent course of localised necrotizing small-vessel vasculitis, which was responsive to B-cell depletion.

A 79-year-old woman presented with acute left periorbital pain, tearing and purulent discharge. The workup included serial microbiological cultures, fungal and mycobacterial testing, molecular diagnostics, CT/MRI/PET-CT imaging, multiple surgical biopsies with histopathology and special stains, ANCA testing, and multidisciplinary treatments (antimicrobials, glucocorticoids, methotrexate and rituximab). The clinical course, laboratory work, imaging studies, histological analysis and response to treatment were thoroughly reviewed.

Initial conjunctival culture revealed C. kroppenstedtii and clindamycin and vancomycin was initiated. Despite escalating antimicrobials, the patient developed progressive inflammation with sinus destruction, cutaneous fistula and cheek abscess, requiring orbital exenteration. The biopsies revealed chronic inflammation with multinucleated giant cells, focal necrosis and small-vessel vasculitis. ANCA remained negative, and subsequent testing was negative. High-dose prednisolone improved the patient, prompting the discontinuation of methotrexate because of pancytopenia. Rituximab-induced remission allowed for steroid tapering and rituximab maintenance, which controlled the disease without complications.

This case illustrates a rare, localised ANCA-negative necrotizing small-vessel vasculitis with destructive orbital involvement and initial detection of C. kroppenstedtii. Although the pathogenic significance of this finding remains uncertain, the case highlights the importance of comprehensive microbiological and immunological evaluation in atypical destructive inflammatory disease. Sustained disease control was achieved with immunosuppressive therapy including rituximab after persistent infection had been excluded.