Concurrent ANCA-associated vasculitis and IgG4-related disease in a patient with fever of unknown origin and acute kidney injury: A case report.

RATIONALE

It is often challenging to differentiate between IgG4-related disease (IgG4-RD) and antineutrophil cytoplasmic antibody-associated vasculitis (AAV) due to their similar clinical presentations. Recently, growing evidence has suggested a strong connection between AAV and IgG4-RD.

PATIENT CONCERNS

A 60-year-old woman was transferred to our hospital with fever and kidney dysfunction. Abdominal computed tomography revealed widespread infiltrative lesions in both kidneys.

DIAGNOSES

Laboratory tests and subsequent renal biopsy confirmed both antineutrophil cytoplasmic antibody-associated vasculitis and IgG4-related disease.

INTERVENTIONS

We initiated plasmapheresis, oral cyclophosphamide, and high-dose glucocorticoids for treatment. Despite this, the patient's condition worsened, requiring emergency hemodialysis.

OUTCOMES

After 3 months of continued immunosuppressive treatment, renal function improved and hemodialysis was discontinued.

LESSONS

Our case showed an overlap of AAV and IgG4-RD, which might support the hypothesis of an overlap syndrome of AAV and IgG4-RD. Clinicians should have a high index of suspicion when diagnosing fever of unknown origin, with the possibility of overlapping AAV and IgG4-RD.