Growth in juvenile idiopathic arthritis: the role of inflammation.

Growth disorders are common among patients with juvenile idiopathic arthritis (JIA). These disorders range from general growth retardation to local acceleration of growth in the affected limb, and are associated with an increased production of pro-inflammatory cytokines, such as interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Pro-inflammatory cytokines may act individually or in combination to impair child growth through systemic mechanisms and/or a local action. Whereas IL-6 affects growth mainly via systemic mechanisms altering growth hormone secretion, IL-1β and TNF-α can directly affect growth plate chondrocyte dynamics as well as longitudinal bone growth. There are emerging data suggesting that interleukin-15 and interleukin-5 may be new cytokines implicated in inflammatory diseases, but further well-designed longitudinal studies in larger groups of children are required to establish a causal relationship. Other factors, which might contribute to growth suppression associated with childhood arthritis, include the degree, extent, and duration of disease activity, age at onset, immobility, sub-optimal nutrition and corticosteroid therapy.