Study cohort
Our study cohort of 43 patients comprised 35 females (81.4%) and 8 males (18.6%), with a F/M ratio of 4.4:1. The mean age at onset was 32.6 (range, 16–54) years [32.2 (range, 16–49) years in females and 34.2 (19–54) years in males]. In the 13 patients (27.9%; 11 females and 2 males) > 40 years of age at the time of diagnosis, all of the other diagnostic criteria of TAK were met but not the ACR criteria for giant cell arteritis (GCA) [24]. Overall, the median diagnostic delay was 23 (range, 9–33) months. The mean length of follow-up for the whole cohort was 51 (9–84) months.
Clinical findings
The clinical features of the patients at diagnosis are described in Table 1. In 5 patients (4 females and 1 male, 11.6%) who were initially asymptomatic, TAK was diagnosed while searching for the cause of an accidentally discovered arterial hypertension (3 patients), in the course of a health examination before starting a new job and in association with obtaining a life insurance policy (1 patient each). In the remaining 38 patients, variable combinations of the signs and symptoms listed in Table 1 were observed. The early inflammatory phase of the disease was typically characterized by non-specific constitutional symptoms, usually with a relapsing/remitting clinical course, whereas in the late, chronic, “pulseless” stage, the clinical picture was dominated by cardiovascular ischemic symptoms reflecting the narrowing, occlusion or dilation of the aorta and/or its main branches [9, 25].
Table 1 Chief complaints at diagnosis in a cohort of patients with Takayasu arteritis Ocular manifestations were detected in 16 of our patients (37.2%), usually late in the course of the disease, and were frequently responsible for severe visual deterioration. These patients are described in detail in a separate report (Dammacco R et al., submitted for publication). Musculoskeletal and neurological features were less frequent, but not rarely were the presenting symptoms of the disease. Renovascular hypertension, often associated with proteinuria and microhematuria, was a prominent manifestation, detected in 7 of the 9 patients with type V TAK and in 2 patients with type IV TAK. Dermatologic findings, mostly erythema nodosum, and abdominal symptoms indicative of gastrointestinal involvement (Fig. 1A) were detected in a minority of patients. A comparative analysis of the clinical findings according to sex showed that constitutional and cardiovascular features were more frequent in female patients, whereas ocular manifestations were diagnosed in a larger number of male patients. The differences, however, were not statistically significant (Table 1).
Laboratory findings
The ESR and the CRP level were increased in 38 (88.4%) and 34 (79.1%) patients, respectively. Hypochromic normocytic anemia (15/43: 34.9%), leukocytosis (19/43: 44.2%), and thrombocytosis (27/43: 62.8%) were detected in patients with disease in the active phase at the time of diagnosis. An additional laboratory finding was polyclonal hypergammaglobulinemia, seen in 53.5% of the patients. None of the 43 patients had abnormalities in renal function. HLA genetic studies were available in 17 of the 43 patients, comprising the subset enrolled from 2009 onward. An association with the HLA-B*52 allele was clearly established in 5 of these patients (29.4%) but in only 4 of 50 (8%) healthy, unrelated Caucasian volunteers from the same geographic area who served as controls (p < 0.02). However, given the low number of typed patients, a relationship between HLA-B*52 and the severity of TAK or the presence of complications could not be firmly established.
Imaging studies
The extensive application of noninvasive imaging techniques is essential to detect arterial wall damage, including arterial stenosis or dilation, to assess the extent and severity of vascular tree involvement, and to monitor the clinical course of the disease and the response to treatment [11, 26, 27]. Our patients were observed over a period of about 13 years, during which time they underwent several noninvasive imaging studies, including at diagnosis and at periodic follow-up examinations.
The most widely used of these techniques was high-resolution color Doppler ultrasonography (CDUS), performed in all patients. Among the findings were a homogeneous, hypo-echogenic, circumferential thickening of the arterial wall affecting to a variable extent and in variable combinations the carotid, subclavian, axillary, and vertebral arteries, either mono- or bilaterally, as well as the abdominal aorta. In several instances, ultrasonography showed a characteristic circumferential thickening of the intima–media complex, a pattern referred to as the “macaroni sign” [12, 28] (Fig. 1B, C) and considered pathognomonic for TAK [29]. Other advantages of CDUS, in addition to its ability to assess intima–media thickness, are the absence of radiation exposure and the easy repetition of the imaging study [30]. However, the technique is operator dependent and unable to accurately image the aortic arch and descending aorta. A more reliable assessment is provided by contrast-enhanced ultrasonography (CEUS), which is more sensitive than serum measurements of acute-phase reactants, such as ESR and CRP, in the monitoring of disease activity and the response to therapy (Fig. 1D) [31, 32].
Computed tomography angiography (CTA) was performed in all patients and provided a clear image of the vessels involved as well as the lumen abnormalities, including stenotic and aneurysmal lesions (Figs. 2 and 3). Based on the angiographic patterns, the disease in each patient was classified according to the five above-described types (Fig. 4). Types I and V were the most common, diagnosed in 25.6% and 20.9% of the patients, respectively, followed by type IIa (18.6%), type IIb (13.9%), type IV (11.6%), and type III (9.3%). The limitations of CTA are the use of iodinated contrast agent, administered intravenously, and the exposure of patients to a high level of radiation.
18F-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) is being used with increasing frequency due to its high sensitivity and the ability to detect the sites, extent, and severity of vessel inflammation. Within our cohort, this angiographic tool was employed in 12 patients (27.9%) at diagnosis and provided clear images of high sensitivity (Fig. 5). However, the limitations of FDG-PET/CT include a rapid decrease in sensitivity in patients treated with GC for 1–2 weeks prior to the examination, high-level radiation exposure, and the possible misinterpretation of the lesions as atherosclerosis [33, 34].
Magnetic resonance angiography (MRA), performed in 9 of our patients (20.9%), provided detailed images of the vascular tree (Fig. 6). The further advantages of MRA include reliable information on luminal and mural changes, the examination of vessels in any suitable plane, the option to obtain serial assessments over time given the lack of exposure to ionizing radiation (a particularly valuable feature in young patients), and the short time required for image generation. The disadvantages include difficulty in visualizing small branch vessels and vessel wall calcifications, and the high cost of the technique [35, 36].
Clinical and imaging-based evaluations often show a variable correlation with the disease course [37]. In the assessment of TAK, MRA and FDG-PET/CT often provide unique and complementary information. Although MRA is more suitable to establish the extent of the disease, FDG-PET/CT is preferred if the goal is to assess vascular activity.
Medical treatment
To understand the rationale of the medical therapies commonly employed in TAK, it is necessary to consider the immunopathogenesis underlying disease onset. Both humoral and cell-mediated immune mechanisms are involved in the pathogenesis of TAK [25, 38]. The persistent activation of immune cells and continued release of proinflammatory cytokines in the aortic adventitia and media result in granuloma formation, fibrosis, scarring and vascularization of the media, disruption of the internal elastic lamina, intimal hyperplasia, and occlusion, with or without thrombosis [39,40,41]. Autoantibodies targeting human heat-shock protein, endothelial cells, and annexin V (a protein that induces apoptosis in vascular endothelial cells) have been detected in TAK patients [42,43,44], but whether they have a pathogenetic role or are an epiphenomenon is unclear. The complex pathogenetic interactions that characterize TAK are depicted schematically in Fig. 7.
Given the inflammatory nature of TAK, and as recommended by the European League Against Rheumatism (EULAR) [45], GC are considered the mainstay of treatment. Their early, usually high-dose administration is essential to control vascular inflammation, achieve clinical remission, and prevent or limit end-organ damage due to ischemia. As summarized in Table 2, all our patients received GC, with an initial daily dose of prednisone ranging from 0.5 to 1 mg/kg that after three weeks was gradually tapered to a maintenance daily dose of 5–10 mg, in step with the attenuation or regression of signs and symptoms as well as the normalization of the ESR and CRP level.
Table 2 Medical treatment in our cohort of 43 patients with Takayasu arteritis Since our patients were recruited in a time frame of about 13 years, their treatment was inevitably heterogeneous. In the first two patients, with type I and IIa disease, respectively, the clinical course was mild and treatment consisted of GC only. However, in the remaining 41 patients an immunosuppressive agent was regularly added to achieve a GC-sparing effect and to reduce the risk of relapse. Within this group, GC were combined with cyclophosphamide in 2 patients and with azathioprine in 13 patients. GC in combination with methotrexate (MTX) were prescribed in 60% of the patients, including 1 patient with type IIb TAK in whom the oral administration of GC was preceded by three intravenous pulses of methylprednisolone because of the occurrence of persistently high fever and a particularly severe clinical picture (Table 2).
Bone protection with bisphosphonates was prescribed to all but 6 patients (in whom these drugs were contraindicated) plus calcium and vitamin D, as appropriate. All patients receiving MTX were also prescribed a folate supplement to reduce the mucosal, gastrointestinal, hepatic, and hematologic side effects. Anti-platelet therapy with aspirin was given to 12 patients, 9 of whom were > 40 years of age at diagnosis. The remaining 13 patients had a moderate lymphopenia and subnormal levels of circulating IgG following long-term GC therapy and were thus treated with three doses of trimethoprim/ /sulfamethoxazole per week to prevent Pneumocystis jirovecii pneumonia.
Remission was achieved in 38 patients (88.4%) in a median of 4.9 (range, 3.3–8.6) months. In 25 of them (58.1%) the remission was sustained, whereas 5 patients (11.6%) had a partial response. One or more relapses were recorded in 12 patients (27.9%), occurring in the first 6 months from the time of the first remission in 9 of them. Of the 7 patients with relapse who had been treated with GC plus tocilizumab, 4 experienced a sustained remission and 3 a partial response. The two patients treated with GC plus MTX plus adalimumab achieved a transient remission, with relapses occurring 3 and 5 months after the discontinuation of adalimumab but still during tapered doses of GC and 10 mg MTX/week. Combination therapy consisting of GC in combination with MTX and the anti-CD19 monoclonal antibody rituximab (RTX) was employed in 3 patients with refractory TAK: two of them were considered to be in sustained remission at the end of treatment and one was lost to follow-up 6 months after the first administration of RTX.
The most common complications of TAK were arterial hypertension (Fig. 3B), with or without renal arterial stenosis (13 patients: 30.2%), and aortic valve regurgitation (7 patients: 16.3%). Visual symptoms and impaired visual acuity caused by steroid-induced cataracts or consequent to restenosis after a patency procedure developed in 4 patients (9.3%) and 2 patients (4.6), respectively; they are described in detail elsewhere (Dammacco R et al. submitted). Three patients died 35, 41, and 57 months after their diagnosis, as a consequence of cerebral hemorrhage, aortic dissection, and myocardial infarction, respectively.