Fluorine-18-fluorodeoxyglucose PET/CT rare finding of a unique multiorgan involvement of Wegener's granulomatosis

Abstract

Wegener's granulomatosis (WG) is an uncommon autoimmune disorder, which mainly involves the blood vessels, kidneys and respiratory tract. We report an interesting case of WG with unusual multiorgan involvement in a young male who presented with a short history of right-sided otalgia, nasal obstruction and a right parotid mass. His initial CT and MRI scans showed a large parotid mass with features suggestive of malignancy with bilateral cavitating pulmonary nodules suggesting metastatic disease. The imaging-based differential diagnosis was squamous cell carcinoma or adenoid cystic carcinoma. The microscopic findings on ultrasound-guided biopsy of the parotid mass were, surprisingly, those of acute necrotising granulomatous inflammation with some features suggestive of a vasculitic process. A multidisciplinary team discussion and further investigation resulted in the additional findings of haematuria, raised erythrocyte sedimentation rate and positive serum cytoplasmic anti-neutrophil cytoplasmic antibody test, which led to the diagnosis of WG. Subsequently, the patient developed acute urinary retention owing to gross prostatic enlargement related to further disease involvement, which was confirmed with a positive biopsy. Fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT scan showed disease distribution at the right maxillary sinus/nasal cavity, right parotid, mediastinum, lungs and prostate. To our knowledge, this is the first reported 18F-FDG PET/CT case with multiorgan involvement in a single WG patient. The patient has improved both clinically and on imaging after appropriate treatment with immunosuppressive therapy and steroids. Although 18F-FDG PET/CT imaging did not actually alter the management of this patient, it can help to establish the disease distribution and guide the biopsy.

Wegener's granulomatosis (WG) is an uncommon autoimmune disorder of unknown aetiology that mainly involves blood vessels (vasculitis), kidneys (glomerulonephritis) and the upper and lower respiratory tract (sinuses, nose, trachea and lungs). It commonly affects both male and females with peak incidence between 40 and 50 years old, but can present at any age.

We report an interesting case of WG with unusual, multiorgan involvement in a 26-year-old male who presented with a 12 week history of right-sided otalgia and neck pain and a right parotid mass associated with ipsilateral facial nerve palsy, nasal obstruction and epiphora.

His initial CT scan showed a large parotid mass with features suggestive of malignancy that was centred in the deep lobe with local extension into the parapharyngeal space laterally, the pterygoid muscle anteriorly and the superficial parotid lobe laterally. Furthermore, there was evidence of bilateral cavitating pulmonary nodules and a soft-tissue mass in the right thigh suggesting metastatic disease.

MRI showed similar features of a locally advanced malignant tumour centred in the deep lobe of the right parotid gland. The imaging differential diagnosis was squamous cell carcinoma or adenoid cystic carcinoma.

An ultrasound-guided biopsy of the parotid mass was performed to confirm the diagnosis. Surprisingly, the microscopic findings were those of acute necrotising granulomatous inflammation with some features suggestive of a vasculitic process.

Multidisciplinary team discussion and further investigation resulted in the discovery of the additional findings of haematuria, raised erythrocyte sedimentation rate and positive serum cytoplasmic anti-neutrophil cytoplasmic antibody (c-ANCA) test, which led to the diagnosis of WG.

Subsequently the patient developed acute urinary retention owing to gross enlargement of the prostate, which was considered to represent further disease involvement and was confirmed with a positive biopsy.

A fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/CT scan (Figures 1 and 2) showed intense increased FDG activity in multiple sites in the body including: the right maxillary sinus and right nasal cavity, the large right parotid mass and its local extension including the middle ear cleft, a large anterior mediastinal mass with few mediastinal and hilar nodes, bilateral cavitating pulmonary nodules, a single peritoneal nodule and diffuse intense FDG activity throughout the prostate gland. To our knowledge, this is the first reported 18F-FDG PET/CT case with multiorgan involvement in a single WG patient.

Figure 1.

(a) Anterior and (b) lateral maximum intensity projection images of the positron emission tomography (PET)/CT scan. A, nasal cavity; B, right parotid; C, anterior mediastinal mass; D, multiple cavitating pulmonary nodules; and E, prostate gland involvement by Wegener's granulomatosis.

Figure 2.

Axial fused images of the fluorodeoxyglucose positron emission tomography CT scan. A, nasal cavity; B, right parotid; C, anterior mediastinal mass; D, multiple cavitating pulmonary nodules; and E, prostate gland involvement by Wegener's granulomatosis.

The patient has improved both clinically and on imaging after appropriate treatment with immunosuppressive therapy and steroids.

Discussion

WG is an uncommon autoimmune disease of unknown aetiology. It presents as a triad of granulomas, necrosis and small vessel vasculitis. Primary involvement occurs in the respiratory tract and the kidneys [1]. Other commonly affected organs include the paranasal sinuses, nasal cavity and nasopharynx and less frequently the orbit, middle ear, musculoskeletal system, nervous system and gastrointestinal system. Multiorgan involvement is not uncommon. At initial presentation the upper respiratory tract is the site usually involved and precedes pulmonary and renal involvement [1]. 90–95% of WG patients have lung and sinus disease and approximately 90% of the patients will develop renal disease [2]. George et al [3] reported a 2% mediastinal and hilar involvement in 302 patients [3]. There are reported cases of prostate gland involvement in patients with WG [4]. Walton [5] reported 7.4% of patients with WG had prostate involvement. In 16% of patients eye symptoms are the first manifestation of WG. Ocular and orbital involvement has been reported in 25–50% of WG patients [6,7]. Neurological involvement in WG primarily involves the peripheral nerves and less frequently the cranial nerves [8-11]. The incidence of cranial neuropathy in WG patients is 6% [12].

The clinical appearance of WG involvement of the salivary glands (especially the parotid and submandibular glands) varies and it might be difficult to differentiate the appearances of WG from other differential diagnoses, such as malignant neoplasm, abscess, sarcoidosis, tuberculosis and infection based on imaging evaluation including 18F-FDG PET/CT scan [13-17].

WG must be distinguished from other causes of vasculitis and granulomatous diseases. Confirmation of the diagnosis should be made by a positive biopsy supported by elevated serological titres of c-ANCA and anti-proteinase-3 (PR3) antibodies (ANCA–PR3), which is found in 91% of patients with WG [18]. The level of c-ANCA is directly proportional to disease activity and titres can therefore be used to measure the disease activity [19,20]. Early tissue diagnosis and c-ANCA titres provide valuable information in the confirmation of the diagnosis, which is required to start appropriate therapy to prevent disease progression and serious complications.

The outcome for patients with WG, after appropriate treatment with immunosuppressive therapy and steroids, is generally good and leads to an improvement in 90% of patients [21]; however, up to 13% of patients may die.

Although 18F-FDG PET/CT imaging did not actually alter the management of this patient, it helped to establish the disease distribution and guide the biopsy. In addition, it can be used as a baseline to assess response to treatment in inflammatory conditions.

Conclusion

Clinicians should be aware of the following points:

• unusual disease distribution of WG can present in a single patient;

• WG should be one of the differential diagnoses of 18F-FDG PET/CT positive scans in non-malignant conditions, in conjunction with appropriate clinical background; and

• 18F-FDG PET/CT imaging in patients with active WG can establish the disease distribution and guide the biopsy.