Diagnostic imaging does not show pathognomonic GPA pattern for early stage symptoms. Mucosal thickening is a non-specific symptom and may be related to other diseases. A characteristic GPA histopathological change in the upper respiratory tract is necrotizing vasculitis. It is a process responsible for the most characteristic paranasal sinus CT symptom – bone damage, accompanied by paranasal sinus opacification. Bone damage is initially centrally located, affecting the nasal septum and the turbinates, and later spreads symmetrically to paranasal sinuses. The final stage of chronic granulomatosis is the conjoining of nasal cavities and paranasal sinuses into one large space, accompanied by bone structure atrophy. The disease then spreads to other structures, including the lamina papyracea and the cribriform plate. In some cases, bone damage is associated with the formation of new bone structure. In CT imaging, bone sclerosis appears as an irregular double line on the sinus wall. This is related to a new layer of bone being formed within the sinus wall. The mechanisms responsible for this growth seem to be of neoosthogenic nature and are not due to periostitis. Similar changes occur after paranasal sinus surgery or in chronic sinusitis. Milford et al. (1986), before CT became commonly used in clinical practice, have described changes seen in the paranasal sinus X-ray in 20 GPA patients. The radiologic signs corresponded to mucosal thickening, opacification, fluid levels, bone damage, and sinus wall sclerosis. Paling et al. (1982) have published similar X-ray data pertaining to 14 patients, who displayed signs of opacification in at least one sinus, and sinus osteosclerosis and osteogenesis. In other studies conducted in similarly small groups of GPA patients, sinus opacification, orbit involvement, bone damage, nasal septum perforation, and mucous inflammation have been reported (Simmons et al. 1987; Yang et al. 2001). Benoudiba et al. (2003), in a study conducted in nine patients, showed that the following characteristic CT changes in GPA patients: nodular mucosal thickening, local bone damage (mainly in the septum and lateral nasal wall, but without ethmoid involvement), ostiomeatal complex involvement and bone demineralization, and the orbit involvement.

Recently, larger groups of GPA patients have been investigated. The most important findings of those investigations are listed in Table 3. Lloyd et al. (2002), on the basis of CT images conducted in 28 GPA patients with no history of nasal or paranasal sinus surgery, have described the following symmetric changes: sinus mucosal thickening, widespread bone damage, and osteogenesis; the findings in comport with our present study. Twenty nine percent of the patients also displayed symptoms of paranasal sinus-related orbital pseudo tumor. In a different study, Lohrmann et al. (2006), apart from the disease signs outlined in Table 3, have found that a small percentage of patients are characterized by partial sinus opacification. In the largest to-date study which analyzed GPA paranasal sinus CT imaging, Grindler et al. (2009) have for the first time used the Lund-Mackay scoring system, basically confirming the findings of others. However, none of the studies outlined above have included data on GPA activity and inflammatory or serological parameters. Those studies were retrospective and dealt with rhinological changes causing sinusitis-like symptoms in GPA patients. The inflammatory changes in the paransal sinuses revealed in our present study were comparable with the results obtained by others. However, we observed less evidence of bone damage and osteogenesis. That might be due to the fact that the study also included patients with normal CT results. Given the lack of data on local and systemic GPA activity in the studies by others outlined in Table 3, no comparative analysis is feasible. However, the present CT and selected GPA activity results showed that the patients with higher L-M score suffered from stronger headaches and more frequently complained of bloody nasal discharge. Although such L-M score-symptom associations have initially been examined for GPA, similar associations occur in case of chronic rhinosinusitis (Nair 2009). That leads to a conclusion that rhinological manifestations and CT findings may appear similar in patients with GPA and chronic rhinosinusitis. The present study also showed an association between the bone damage, visible in CT imaging, and the extension of time from the appearance of first symptoms to diagnosis. In all patients, diagnosis was linked with the initiation of systemic glucocorticosteroid and cyclophosphamide treatment. It appears that this treatment considerably decreases nasal bone damage. On the other hand, the prolonged presence of symptoms prior to diagnosis facilitates destruction of sinonasal anatomy. We found no associations between L-M score, symptom duration, and the time from diagnosis. However, L-M score was apparently associated with mupirocin treatment. Mupirocin is a topically applied antibiotic produced by Pseudomonas fluorescens. The antibiotic inhibits protein and RNA synthesis and is applied for treatment of chronic colonization by Staphylococcus aureus. Although Staphylococcus aureus carriage not always requires treatment in healthy persons, treatment is recommended in instances of immunodeficiency, e.g., during immunosuppressive therapy. The treatment is particularly important in GPA as Staphylococcus aureus colonization may lead to disease relapse (Zycinska et al. 2008).