Giant cell arteritis (GCA) is a disease that relapses often, and some patients run a refractory course. Although prompt recognition of resistant GCA is a major issue, there is no well-recognized, baseline risk factor for poor response to glucocorticoid (GC) treatment.
We included all patients consecutively diagnosed with GCA and homogeneously treated since 1976 in a single department and regularly followed-up for at least 18 months. Using a set of customized criteria defining response to GCs, we separated patients into highly responsive, usually responsive, dependent on GCs, and resistant to GCs. We determined which of the baseline variables were associated with GC-resistance and conducted factor analyses of mixed data and decision tree analyses. We also determined whether being GC-resistant was associated with poorer tolerance to GCs and higher death rates.
In all, 455 patients were followed for 93.4 ± 67.6 (standard deviation) months; 41 (9%) and 21 (4.6%) patients developed GC-dependent and GC-resistant disease, respectively. Factor analyses suggested an association between clinical pattern and degree of responsiveness to GCs; The decision tree analyses, built on an age at GCA onset 〈 66 years and body weight 〉 71 kg, delineated a high risk profile (44% of the patients who featured both characteristics were GC-resistant vs. less than 3% who featured neither, p < 0.001). Infections were more prevalent in the GC-resistant or GC-dependent patients, but without decreasing their survival.
Extra-cranial, large-vessel GCA may be associated with prolonged GC requirements. A simple combination of age and body weight defined a subgroup of patients at high risk for developing GC resistance. Our findings need confirmation in prospective controlled studies.