Granulomatosis with polyangiitis in Northeastern Brazil: study of 25 cases and review of the literature

Granulomatosis with polyangiitis (GPA) is a rare systemic disease of the pauci-immune vasculitis spectrum associated with antineutrophil cytoplasmic antibodies (ANCA) [1] and affecting mainly the upper respiratory tract, lungs and kidneys [2]. Approximately 85% of GPA patients are ANCA-positive, with proteinase 3 (PR3) as the most commonly observed antigen (~ 75%) [3, 4].

GPA affects mostly adults, especially Caucasians, with no gender predominance [1]. The mean age at diagnosis is 50 years [5]. GPA is usually treated with a combination of glucocorticoids and cyclophosphamide, inducing remission in most patients [6]. The recent introduction of rituximab has further increased the rates of remission maintenance [7, 8].

The etiology of GPA is unknown, but the frequent early involvement of the upper respiratory tract suggests an environmental cause. Epidemiological studies from the northern hemisphere also support the notion of environmental risk, as reflected in regional differences in prevalence and incidence and the existence of a North-South negative gradient (the incidence of GPA is higher in Northern Europe than in Southern Europe) [5, 9, 10]. Genetic and geographical factors may explain these differences [10–12].

Little has been published about the epidemiology of GPA in South America, especially in the intertropical zone, and no epidemiological data from Brazil are available [13–17]. The only two Brazilian studies investigating the clinical and laboratory profile of GPA patients reported a spectrum of clinical manifestations similar to that found in the international literature [13, 14]. However, these Brazilian studies on GPA were conducted outside the intertropical zone [13, 14].

The purpose of the present study was to draw a clinical and demographic profile of GPA patients living in Northeastern Brazil based on laboratory, histological and imaging findings, and evaluate the frequency of organic involvement in relation to data from the international literature.

This is the largest retrospective multicenter study to draw a clinical and epidemiological profile of patients with GPA from Northeastern Brazil and the first to systematically use BVAS and VDI scores. Compared to the international literature, the upper respiratory tract and the lungs were less frequently affected in our patients from Northeastern Brazil [11, 13, 25]. The most frequent disease extension was generalized, and time to diagnosis was relatively long (in one case, 18 years from the onset of symptoms).

Our sample was predominantly female (84%; M/F ratio: 0.2). Gender distribution is known to be influenced by geographical variables [10]. For example, the female gender was predominant in a study from Southern Europe while the male gender was predominant in a study from Northern Europe [5, 10]. Within the southern hemisphere, the male gender is predominant in New Zealand (43°S) (M/F ratio: 1.2) and Argentina (31°S) (M/F ratio: 1.2), while the female gender is predominant in Chile (33°S) (M/F ratio: 0.8) and São Paulo (23°S) (M/F ratio: 0.9) [11, 13, 15, 16]. In short, available data suggest a tendency for female predominance among GPA patients at low latitudes in both hemispheres [10].

The average age at diagnosis in the present study (42 years) was similar to that observed in studies from São Paulo (43.4 years) and the U.S. (41 years) [1, 13], but GPA patients from Chile (50.8 years), Australia (55 years), New Zealand (66 years) and Italy (58.8 years) were significantly older [10, 11, 15, 26], possibly due to differences in geographical variables and/or in methodology. In fact, populational studies suggest GPA is more frequent in older individuals whereas case studies conducted at hospitals show a lower age at diagnosis [5, 27, 28].

Matching the literature, ENT was the most frequently involved organ system, followed by the lung [1, 5, 10]. The most frequent pulmonary manifestation was pulmonary nodules, as observed in other studies conducted in the southern hemisphere [11, 13]. Sinus disorder was the main manifestation of ENT involvement observed, but the frequency was still significantly lower in our study than in studies from Southeastern Brazil and New Zealand [11, 13]. The observed prevalence of skin involvement (32%, all of which included purpura) was comparable to that reported in another Brazilian study and in studies conducted in the northern hemisphere. With a frequency of less than 30%, PNS involvement (predominantly axonal polyneuropathy) was within the range reported worldwide [1, 13, 29]. Ocular involvement was less frequent in Northeastern Brazil (n = 1; 4%) than in New Zealand (n = 15; 20%) [11].

The observed frequency of cardiac involvement (16%) matched the findings of other epidemiological studies but was lower than the frequency reported in case studies (25–46%) [30]. CNS and gastrointestinal tract involvement was rare, as in most other studies [13, 29].

Two thirds (4/6) of our patients with 24-h proteinuria > 1 g at the time of diagnosis developed CKD after one year, with three patients requiring permanent dialysis. According to Neumann and coworkers, high levels of proteinuria at diagnosis in patients with ANCA-related glomerulonephritis may be predictive of poor renal prognosis [31]. The present study was limited by the unavailability of follow-up data to determine the frequency of development of CKD in patients with normal urine protein output (or < 1 g) at the time of diagnosis. An expressive number of patients in our sample presented proteinuria in the nephrotic range (31%). The degree of proteinuria in patients with GPA is most often subnephrotic [1]. High levels of proteinuria (> 3 g/day) seem to be most common in patients who present later in the course of the disease and who have had previous necrotizing glomerulonephritis, leading to more focal and segmental glomerulosclerosis/fibrosis at the time of presentation. On the other hand, GPA patients with high levels of proteinuria may have a concurrent glomerular disease (e.g., membranous nephropathy) or an atypical histological pattern characterized by glomerular immune complex deposition [32, 33].

Patients with BVAS scores below and above the cohort average did not differ with regard to the frequency of renal involvement. Two patients who developed CKD had low BVAS scores (< 6) at diagnosis, suggesting factors other than kidney damage (possibly old age and late diagnosis and treatment) contributed to the poor prognosis in these cases.

Our ANCA positivity rate (87.5%) was compatible with international reports (85%) [4]. All patients presenting with the limited form of the disease were ANCA-positive. This is higher than previously published rates (up to 40% ANCA negativity) [4]. The fact that only 4 ANCA-positive patients were submitted to anti-PR3 ELISA (c-ANCA n = 3; p-ANCA n = 1) was an unfortunate limiting factor in our clinical and epidemiological analysis of the anti-PR3 profile of GPA patients from Northeastern Brazil. The infrequent use of anti-PR3 ELISA in our sample prevented the adoption of GPA classification criteria based specifically on this assay (e.g., modified ACR) [34]. On the other hand, the use of the EMA algorithm offered the possibility of detecting ANCA by indirect immunofluorescence in settings with little or no access to anti-PR3 ELISA [19]. The EMA algorithm uses the 1990 criteria of the American College of Rheumatology (ACR) and the definition of the Chapel Hill Consensus Conference, in addition to the criteria of positive serology for ANCA [19, 35, 36].

ANCA-positive patients with high titers (1:640) (7/7) had low BVAS scores at diagnosis. While there is no consensus on the role of ANCA positivity in the prognosis of GPA patients, Finkielman and colleagues concluded that high ANCA titers were not predictive of disease activity, activity score or organ system affected at the time of recurrence [37].

The observed differences in the frequency of certain types of clinical manifestations (e.g., ENT and pulmonary) between Northeastern Brazil and other regions in the northern and southern hemispheres may be explained by the influence of environmental and latitudinal factors on clinical phenotype. One study showed an inverse relation between GPA incidence and the intensity of UV radiation at specific latitudes, implying Vitamin D synthesis is a major detemining factor of the observed gradients [12]. The fact that only 30% of our cohort was Caucasian (the remainder being of primarily indigenous race) should be taken into account when interpreting our findings.

The cohorts of most European studies consist almost exclusively of Caucasians [9, 38]. Likewise, in a U.S. cohort study, over 90% of GPA patients were Caucasian while only 4% were Afro-American, Hispanic or Asian [1].

Improvement in kidney function after combination therapy with glucocorticoids and cyclophosphamide is well documented and is known to revert kidney damage in patients presenting with kidney failure [39]. In the present study, half the patients (4/8) treated endovenously with cyclophosphamide due to glomerulonephritis with creatinine clearance < 50 mL/min at the time of diagnosis recovered kidney function. The other 4 developed CKD, 3 (38%; 3/8) of whom requiring permanent dialysis. Based on its successful use in ANCA-positive vasculitis and its greater likelihood of effectiveness against recurrence (compared to cyclophosphamide) and greater effectiveness at maintenance (compared to azathioprine), rituximab was administered to 32% of our patients, three quarters of whom presented renal involvement [7, 8, 40].

The incidence of infection (including two cases in which infection contributed to the fatal outcome) was low in our cohort. Physicians in Northeastern Brazil are advised to include tuberculosis (a granulomatous disease highly prevalent in the region, with clinical manifestations not unlike those of GPA) in the differential diagnosis of GPA [41]. Despite the fact that some of our patients had a history of contact with, or treatment for, or chest x-rays suggesting tuberculosis (e.g., cavitations and tree-in-bud), no active tuberculosis was observed. However, few patients in our cohort were submitted to the Mantoux test, especially those diagnosed in the five years preceding the study. This is partly due to a lack of supplies in the Brazilian public health care system (SUS) nationwide and partly due to limited access to testing for lymphocyte response against M. tuberculosis (interferon-γ release assay). In addition, the frequency of ANCA positivity among patients diagnosed with tuberculosis can introduce a bias in the investigation of suspected cases (10–33% of patients with this condition are ANCA-positive) [42].

Two early deaths (within one year of diagnosis) occurred during the study period (8%). This is compatible with other studies reporting 6–11% early mortality from GPA [43, 44].

The study has a number of limitations as a result of the retrospective design, the inclusion of multiple centers and the extensive period sampled. Thus, the collected information was not always homogenous and complete. The lack of serial follow-up made it impossible to evaluate renal survival and compare clinical and prognostic factors. Possible loss to follow-up associated with difficulties in the diagnosis of the limited form of GPA and high mortality rates among patients with the diffuse form may have led to underreporting.

In this study from Northeastern Brazil, most patients were female, had the generalized form of the disease, presented nephritic syndrome during the evolution of the disease and were diagnosed late. Overall, the frequency of clinical manifestations was comparable to that reported in the international literature, with some differences in relation to the northern hemisphere (pulmonary and renal involvement) and the southern hemisphere (ENT involvement), suggesting the existence of a Northeast Brazilian clinical and epidemiological profile and adding to our knowledge of this rare condition.