Physiopathologie de l’artérite à cellules géantes

[Giant cell arteritis: Ischemic complications]

GCA ischemic complications occur generally in patients with a yet undiagnosed or uncontrolled disease. When disease control is fair, ischemic complications may be due mostly to atheromatosis. Ophtalmic complications are most frequent and are dominated by anterior ischemic optic neuropathy. Vasculitic strokes occur essentially in the vertebrobasilar arterial territory. Overt vasculitic coronary disease is exceptional. The diagnosis of upper and lower limbs ischemic complications benefit from advances in echography (halo sign) and positron emission tomography imaging. Treatment relies on corticosteroids (initially 1mg/kg prednisone or more, preceded by intravenous methylprednisolone gigadoses if necessary), the control of cardiovascular risk factors and antiplatelet drugs; heparin may be indicated for threatening limbs ischemia.

Does low risk of infections as a marker of effective immunity predict increased risk of subsequent giant cell arteritis or polymyalgia rheumatica? A Danish population-based case-control study

Objective

It has been suggested that a hyper-effective immune system (“hyper-immunity”) is central to the pathogenesis of giant cell arteritis and polymyalgia rheumatica (GCA/PMR). We examined if a low risk of infections, as a marker of hyper-immunity, can predict increased subsequent risk of GCA/PMR.

Patients and methods

We conducted a population-based case–control study including all patients aged ≥50 years with incident GCA/PMR diagnosed between 1997 and 2012 in Northern Denmark. For each case, we selected 10 population controls matched on gender, age, place of residence, and time spent in the region. Complete history of hospital-treated infections and community-based anti-infective prescriptions was assessed in population-based registries. We used conditional logistic regression to compute OR of GCA/PMR associated with infections while adjusting for comorbidities, immunosuppressive treatment, and other potential confounders.

Results

We included 7,225 GCA/PMR cases and 72,250 controls. When excluding all infections occurring within the last year before GCA/PMR diagnosis, there was no decreased risk for GCA/PMR in people with a history of hospital-treated infection (adjusted OR=1.04, 95% CI: 0.98–1.10) or community anti-infective treatment (adjusted OR=1.07, 95% CI: 0.99–1.16). Within the last year preceding the GCA/PMR index date, patients with hospital-treated infections (adjusted OR=1.59, 95% CI: 1.44–1.75) or community anti-infective treatment (adjusted OR=1.63, 95% CI: 1.48–1.79) had a greatly increased risk of a GCA/PMR diagnosis.

Conclusion

These results do not support the hypothesis of “hyper-immunity” leading to GCA/PMR. Instead, incident GCA/PMR is preceded by a slightly increased risk of infection, which may be related to protopathic bias or support theories that infections may be directly involved in the pathogenesis of GCA/PMR.

Treatment of giant-cell arteritis, a literature review

Giant-cell arteritis (GCA) is the most common vasculitis in people aged more than 50 years. Despite the frequency of this disease, there is currently no international consensus on its therapeutic modalities. The aim of this study was to conduct a review on an international literature about the treatment of GCA, whatever the clinical pattern might be. Oral corticosteroids remain the cornerstone treatment, possibly preceded by intravenous bolus in complicated forms. In cases of glucocorticoid (GC) dependence or GC-related side effects, a GC-sparing agent may be necessary. Methotrexate is one of the most used treatments despite its low level of evidence and mild efficacy. Cyclophosphamide and tocilizumab look promising but require validation in further studies. The results for TNF-α blockers and azathioprine are disappointing. Preventing complications of prolonged corticosteroid therapy is a world challenge and the management of GC-induced osteoporosis is not the same from one country to another. There is a significant risk of arterial thrombosis, mainly at treatment onset, which may encourage to associate an antiplatelet therapy, especially in patients with other cardiovascular risk factors. Place of statins in the treatment of the disease is uncertain.