Early Stage Graves' Disease is Uniformly Accompanied by Orbital Immune Activity even in Patients who Fail to Develop Orbithopathy during Follow-up

Purpose: Graves' orbitopathy (GO) is a complication of Graves' disease (GD), the development of which cannot be predicted at the time of diagnosis of GD. Our aims were (i) to test if orbital ^99mTc-labelled diethylenetriamine pentaacetic acid single-photon emission computer tomography (DTPA SPECT) can predict development of GO later during the course of the disease and (ii) to study whether orbital immune activity can be detected in GD patients who do not develop GO during follow-up.

Methods: Fifty-four orbits of 27 patients with newly diagnosed GD were entered into the case-control study. Individuals showing signs of GO at enrolment were excluded. During the two-year follow-up, eye signs were recorded every 3 months. Orbital DTPA uptakes on SPECT images were measured when entering the study and at the end of the follow-up period, or when clinical signs of GO developed, whichever occurred first.

Results: During the follow-up, 6 patients (22%) were diagnosed with GO. There was no significant difference between the initial DTPA uptakes of the patients with or without later developing GO (10.45±1.72 MBq/cm³ vs. 9.18±1.18 MBq/cm³ respectively). However, the DTPA uptakes of both GD groups (ie. with and without GO) were higher than that of the control group (7.45±1.36 MBq/cm³, p<0.05).

Conclusions: We have shown that GD is accompanied by moderate orbital immune activity in GD patients without GO, irrespective of later development of GO. Why this orbital autoimmunity remains subclinical in the majority of the cases, and progresses into clinically detectable GO in others, remains unclear.