Should Graves' Disease be Considered a Collagen Disorder of the Thyroid, Skeletal Muscle and Connective Tissue?

Abstract

Graves' disease corn prises hyperthyroidism, ophthalmopathy, pretibial myxedema and acropachy, which occur separately or in various combinations. We have used the indirect immunofluorescence test to investigate reactivity of sera from patients with autoimmune thyroid disorders with and without ophthalmopathy, with porcine extra ocular muscle (EOM) and control tissue substrates. Sera from 75% of patients with Graves' hyperthyroidism (GH) and ophthalmopathy, which we call thyroid-associated ophthalmopathy (TAO), contained one or more antibodies reactive with EOM compared to 32% of those with GH without the eye disorder, 41% of patients with Hashimoto's thyroiditis (HT), and 16% of normals. Antibodies reactive with an FOM connective tissue antigen(s), seen as fluorescence of the interstitium and endomysium, were found in sera from 10% of patients with TAO and 16% of those with GH, but not from any patient with HT or normal subject. Similar patterns of connective tissue reactivity were also found in lacrimal gland, skeletal muscle, kidney and salivary gland. Antinuclear antibodies were detected in sera from 31% of patients with TAO, but from only 8% with HT, in no patient with GH and in only 3% of normal subjects. The most common pattern was a fine speckled fluorescence, found in 45% of sera, consistent with reactivity against the Sm antigen or nuclear RNP. The finding of a high prevalence of ANA and, less often, anti-connective tissue antibodies in patients with thyroid autoimmunity and ophthalmopathy, is consistent with Graves' disease being a “collagen-like disorder”. The reason why inflammation and resulting tissue damage is limited to the thyroid, connective tissue of the skin and orbit, skeletal muscle and, possibly, the lacrimal gland, is unclear. One possibility is cross reaction of ANA with tissue specific membrane proteins in these sites. The extent of immunologic abnormalities, and the resulting clinical features, in patients with Graves' disease may reflect the severity of a putative defect in immune regulation.

Key words

Graves' Disease - Thyroid-Associated Ophthalmopathy - TSH-Receptor - Extra Ocular Muscle - Antinuclear Antibodies - Collagen Disorder