Role of connective tissue autoimmunity in Graves' ophthalmopathy

Histologic similarities exist between the tissues involved in the extrathyroidal manifestations of Graves' disease, namely ophthalmopathy and pretibial dermopathy. Both conditions are characterized by an accumulation of glycosaminoglycans (GAGs) and an infiltration of lymphocytes. We have shown that interleukin-1 and transforming growth factor-beta, cytokines released by the local inflammatory cell infiltrate, are capable of stimulating GAG synthesis by retroocular and pretibial fibroblasts. Additionally, affected retroocular and pretibial fibroblasts demonstrate an enhanced induction of HLA-DR in response to interferon-gamma treatment and both cell types express the 72 kDa heat shock protein in vivo and in vitro. Retroocular and pretibial fibroblasts from patients with Graves' ophthalmopathy and pretibial dermopathy thus seem to possess unique immunological features that may render them more susceptible to the autoimmune process in Graves' disease. Chronic stimulation of fibroblasts by cytokines released in the local inflammatory milieu may result in excessive GAG production. The accumulation of these hydrophilic mucopolysaccharides, with its associated edema, leads to the clinical manifestations of Graves' ophthalmopathy and pretibial dermopathy.