Rheumatology Advance Access originally published online on April 29, 2008
Rheumatology 2008 47(7):1031-1037; doi:10.1093/rheumatology/ken136
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Age-dependent inhibition of ectopic calcification: a possible role for fetuin-A and osteopontin in patients with juvenile dermatomyositis with calcinosis
1Department of Paediatrics, Trondheim University Hospital, 2Department of Laboratory Medicine, Children's and Women's Health, The Norwegian University of Science and Technology, Trondheim, Norway, 3Department of Rheumatology, Great Ormond Street Hospital for Children, 4Department of Infectious Disease and Microbiology, 5Department of Nephrourology, 6Department of Rheumatology and 7Rheumatology Unit, UCL Institute of Child Health, London, UK
Correspondence to: P. A. Brogan, Department of Rheumatology, Institute of Child Health, 30 Guilford St London WC1N 1EH. E-mail: p.brogan{at}ich.ucl.ac.uk
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Abstract |
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Objectives. To assess if age and/or age-dependent variations in the levels of two major calcification regulatory proteins, fetuin-A and osteopontin, could be associated with an increased risk of calcinosis in children with juvenile dermatomyositis (JDM).
Methods. The frequency of calcinosis was derived from a national UK database of 212 cases of JDM. Serum fetuin-A and plasma osteopontin levels were determined using ELISA in 15 JDM patients with calcinosis and 15 JDM patients without calcinosis. Healthy controls were 19 age-matched children, 24 adolescents and 13 adults. Sixteen patients with juvenile idiopathic arthritis (JIA) were additional paediatric disease controls.
Results. Of the 212 JDM cases 10% had calcinosis. Calcinosis patients had younger age of disease onset than those without calcinosis (mean age of 5.3 yrs vs 7.1 yrs, respectively, P = 0.016). No significant difference in fetuin-A or osteopontin could be detected between the two JDM groups. Fetuin-A levels in all groups of children and the adolescent group were much lower than described previously in adults, and there was a significant positive correlation between age and fetuin-A level, and also between osteopontin levels in plasma and serum fetuin-A.
Conclusions. Children who develop JDM at an younger age may have increased risk of developing calcinosis. Physiologically low levels of fetuin-A in young children combined with an additional negative acute-phase effect on fetuin-A due to chronic inflammation could explain in part the propensity to develop ectopic calcification observed in JDM patients, and why calcinosis is less frequent in adults with dermatomyositis.
KEY WORDS: Juvenile dermatomyositis, Calcinosis, Fetuin-A, Osteopontin
Submitted 20 December 2007;
revised version accepted 13 March 2008.
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