Increased ferritin response in adult Still's disease: specificity and relationship to outcome

Abstract

Background: The disproportionate ferritin response encountered in some patients with adult Still's disease (ASD) may reflect a fundamental aspect in the pathophysiology of ASD.Methods: An observational case–control study of 22 ASD patients followed for 63 months. Baseline laboratory data were compared with age‐ and gender‐matched controls with new‐onset rheumatoid arthritis (RA). Serum levels of ferritin and C‐reactive protein (CRP) and the ferritin/CRP ratio were related to clinical outcome in ASD through nonparametric statistical analyses.Results: Compared to RA patients, haemoglobin levels were lower (11.8 vs. 13.5 g/dL; p = 0.009) and leucocyte counts (17.1 vs. 8.6 109/mL; p<0.001), erythrocyte sedimentation rate (ESR) (84 vs. 38 mm; p = 0.001), CRP (154 vs. 27 mg/L; p<0.001), aspartate aminotransferase (ASAT) (52 vs. 23 U/l; p = 0.004), serum ferritin (8750 vs. 62 µg/L; p<0.001) and ferritin/CRP ratios (9.7 vs. 1.7; p<0.001) were higher in ASD patients at baseline. Six patients (27%) achieved sustained remission (monocyclic disease), while 16 patients (73%) developed chronic disease (progressive in 27%, relapsing/remitting in 46%). The levels of ESR and CRP or other baseline variables were not associated with outcome. However, baseline serum ferritin was significantly higher in ASD patients with chronic disease (p = 0.04), while a cut‐off of five times the normal upper level (NUL) was 100% sensitive and 60% specific for predicting chronic disease.Conclusion: An exaggerated ferritin response with levels>5 times the NUL and high ferritin/CRP ratios is useful for distinguishing between ASD and RA patients. Ferritin levels>5 times the NUL are also associated with a chronic disease course.