Late reactivation of thyroid orbitopathy

BACKGROUND:Thyroid orbitopathy is characterized by spontaneous remissions and exacerbations. Although data on the natural history are scarce, the active phase is usually self-limited, encompassing an average period of 18-36 months. Late reactivation, defined as active orbitopathy occurring after more than 5 years of quiescent disease, appears to be an uncommon and poorly documented event. The aim of the present study was to assess the incidence and characteristics of late reactivation of thyroid orbitopathy within a tertiary referral orbital clinic. METHODS:A retrospective case review was conducted of patients with thyroid orbitopathy seen at the Royal Adelaide Hospital Orbital Clinic between 1996 and 2001. RESULTS:From 193 cases of thyroid orbitopathy, eight cases (5%) of late reactivation were identified. The mean age of patients was 51 years (range 32-76 years) with a female to male ratio of 3:1. All cases presented with proptosis and seven demonstrated increased diplopia and gaze restriction. Signs of soft tissue inflammation were seen in three cases. All were euthyroid at presentation with a past history of thyroid orbitopathy and hyperthyroidism. One patient had an association of smoking with reactivation but the remainder had no discernible precipitants. The average interval between the initial orbitopathy and reactivation was 12 years (range 6-30 years). Computed tomography revealed enlarged extraocular muscles in seven cases and two showed partial response to treatment with low dose radiotherapy and steroids. The average length of disease activity was 14 months (range 9-18 months). CONCLUSION:Late reactivation of thyroid orbitopathy appears to be an uncommon phenomenon. It may occur under euthyroid conditions with no obvious precipitants and often presents as a reactivation of myopathy.Dinesh Selva, Celia Chen and Georgina Kin