A 60-year-old patient was admitted to our hospital because of inflammatory syndrome, polyarthralgia, and weight loss. A physical examination showed only pain in the heels and the first metatarsophalangeal joint as well as hypoesthesia of the left foot. The significant biological results showed nonidentified c-ANCA (non-PR3 and non-MPO) with a titer of 1 : 2560 as well as a C-reactive protein of 99 mg/L, and an erythrocyte sedimentation rate of 67 mm/h. The renal function was in the normal range values. The thoracic computed tomography (CT) scan showed several bilateral nonspecific micronodules (Figure 1(a)), and the positron emission tomography computed tomography (PET-CT) scan showed moderately hypermetabolic retroperitoneal and inguinal lymphadenopathy. A sinus CT scan was performed and showed pansinusitis (Figure 1(b)). A biopsy of inguinal adenopathy was performed in favour of reactive inflammatory nodes with no signs of malignancy. The tuberculosis QuantiFERON ELISA test was positive, but the culture and polymerase chain reaction of the biopsied node were negative. The patient later developed arthritis in the ankle confirmed by IRM, and sinus CT confirmed the presence of pansinusitis. The diagnosis of GPA was made on the basis of high c-ANCA titers (non-PR3 and non-MPO), bilateral pulmonary nodules, and pansinusitis, and treatment with cyclophosphamide and methylprednisolone was administered, followed by azathioprine. This treatment was combined with isoniazid for tuberculosis prophylaxis. The patient presented a good clinical evolution with normalisation of the inflammatory syndrome and a significant decrease in c-ANCA (Figure 2). Five years later, the patient's clinical condition deteriorated with asthenia, weight loss, and abdominal pain. There was an increased inflammatory syndrome as well as increased ANCA titers (variation of titers is shown in Figure 2). The PET-CT scan was not in favour of a vasculitis relapse. The node biopsy performed five years ago was retrospectively reviewed for evaluation of IgG4. The histology of the lymph node was described as an inflammatory node with extensive plasmacytosis as depicted with CD138 immunostaining. The infiltrate showed 50 IgG4 positive plasma cells per high-power field. A serum IgG4 assay was performed and very slightly increased at 1.351 g/L (N < 1.350). The abdominal CT image did not show retroperitoneal fibrosis despite the presence of bilateral uretero-hydronephrosis without objectified obstacle. A possible diagnosis of IgG4-related disease (IgG4-RD) was then carried out, but GPA diagnosis was not completely excluded. The patient was treated by intravenous methylprednisolone and rituximab with a good clinical and biological evolution. Three years later, he developed another relapse with distal digital ischemia of the foot, multiplex mononeuritis, and external popliteal sciatica deficit, rather in favour of GPA with a BVAS score of 6 (Birmingham Vasculitis Activity Score). Afterwards, the patient was treated only with mycophenolate mofetil (2 g/day) without any relapse.