Long-term multidisciplinary follow-up of unilateral thyroid-associated orbitopathy.

BACKGROUND: Thyroid-Associated Orbitopathy (TAO) is an autoimmune disease characterized by orbital inflammation involving both adipose tissue and extra-ocular muscles (EOM). Whereas bilateral and possibly asymmetric orbital involvement is commonly found at radiological work-up, mono-orbital involvement is poorly documented, and ascribed to an initial and/or transient stage of subsequent bilateral TAO. METHODS: From a cohort of two hundred TAO patients, we selected retrospectively fourteen patients with initial clinical unilateral TAO. Five of them were excluded because of clinical bilateralization. RESULTS: The sex ratio was 0.8 (4M, 5F), and mean age 44.6 years (range: 18-63). All patients were euthyroid when the initial magnetic resonance imaging (MRI) was performed. One patient was treated with Levothyroxine, because of subclinical hypothyroidism. Eight patients (six smokers) suffered from Graves' disease, of 1-4 years duration, for which they were treated with antithyroid drugs. A thyroidectomy was performed in two patients. None of the patients ever received radioiodine. Six patients remained euthyroid after stopping of the antithyroid regimen, and two became hypothyroid. Seven patients had active, and two severe TAO. Four of nine patients exhibited bilateralization of TAO on initial MRI. Clinical status ultimately improved or normalized in all. In two patients, MRI performed after 9 years demonstrated partial shrinkage of previously enlarged EOMs, together with fatty involution of involved muscles. CONCLUSIONS: Unilateral TAO is not different and just as severe as bilateral TAO. At initial work-up MRI shows signs of bi-laterality in 45% (4/9), with mild involvement of 1 or 2 extra-ocular muscles. The radiological status of affected muscles does not normalize, even in the very long term.