Pediatric-onset limited ANCA-associated vasculitis arising during pre-existing chronic recurrent multifocal osteomyelitis.

Background: Granulomatosis with polyangiitis (GPA) is an autoimmune disease characterized by chronic vasculitis involving small to medium sized arteries, granulomatous inflammation of the upper and lower respiratory tracts, pauci-immune necrotizing glomerulonephritis, as well as vasculitis of other organs. Chronic recurrent multifocal osteomyelitis (CRMO) is an autoinflammatory syndrome characterized by sterile bone inflammation.

Case Presentation: We report a case of CRMO that was doing well on non-steroidal anti-inflammatory drugs (NSAID for 6 years and then developed ANCA positive limited GPA presenting with pyoderma gangrenosum, persistent bilateral otalgia with serous otitis, otorrhea, then sensorineural hearing loss.

Conclusion: This is the first report of limited GPA initially presenting as pyoderma gangrenosum in a patient with underlying CRMO. It is unclear how the pathology of an autoimmune and an autoinflammatory condition can overlap.