Case Presentation: 72-year-old Caucasian woman with PMH of cervical spinal stenosis presented with one-month history of worsening generalized weakness and soreness in all her extremities. Three months prior she had complained of persistent headaches for which she took ibuprofen with limited relief. Suspected of having GCA based on ESR 75 mm/hr with no biopsy at the time, she was started on prednisone 60mg oral daily with tapering which provided relief. However, when the prednisone dose was down to 10mg, the headaches started to reoccur along with her new complaints. On physical exam, her vital signs were normal, and findings were notable for tenderness in bilateral temporal areas and in the muscle groups of all extremities with weakness of lower extremities. Initial workup revealed BUN 62mg/dl, creatinine 2.8mg/dl, random urine protein 76mg/dl with 24-hour urine protein 576mg but no urine RBCs, ESR 81mm/hr, CRP 170mg/l, total CPK 245u/l, and positive MPO-ANCA with titer >8. Bilateral temporal artery biopsies revealed chronic inflammation on the left, and acute on chronic inflammation with rare giant cells on the right, both with elastic stains showing disruption of the internal elastic lamina, all consistent with GCA. Renal biopsy revealed necrotizing vasculitis, extensive tubulitis and interstitial inflammation, all consistent with MPO-ANCA-associated vasculitis. Immunofluorescence showed no evidence of immune complex glomerular disease. Recommended treatment included steroid taper and cyclophosphamide with consideration for rituximab if adequate response not achieved later.

Discussion: Giant cell arteritis (GCA) is categorized as a medium-to-large vessel vasculitis. Although an elevated ESR and/or CRP in combination with the clinical findings are highly suspicious of GCA, temporal artery biopsy is highly recommended in all suspected patients. However, a negative biopsy or absence of giant cells does not rule out the disease given the possibility of skip lesions. In contrast to small vessel vasculitides which can be linked to ANCA, large vessel vasculitides have no known associated antibody expression patterns. Here we present an extremely rare phenomenon in a patient with biopsy-proven bilateral GCA with renal failure in whom kidney biopsy was consistent with AAV.

Conclusions: Renal involvement in patients with GCA is quite rare, and to the best of our knowledge, only two cases have been reported with clear documentation of association with AAV. Majority of patients with renal limited vasculitis are seropositive for ANCA, mostly MPO-ANCA. The patient in this case being MPO-ANCA positive with renal vasculitis and GCA represents an extremely rare clinical overlap between small, medium and large vessel vasculitis. In all patients diagnosed with GCA, care should be taken to closely evaluate for possible associated renal disease. Doing so has important therapeutic implications as GCA has good clinical response to steroids, but the presence of renal vasculitis requires the addition of another immunosuppressant such as cyclophosphamide.