ESPE Abstracts

Introduction: Graves' disease (GD) is an autoimmune hyperthyroidism characterized by the presence of TSH receptor antibodies (TRAb) present in 95% of cases. GD is the most common cause of exophthalmos, which is unilateral in 15% of cases, and falling within the framework of Graves orbitopathy (GO). GO concerns half of patients with GD. The presence of GO is very rare in patients with negative TRAb.

Observation: This is a 12-year-old girl, with no previous history, who consulted for a right unilateral exophthalmos, of sudden onset, associated with pain. On ophthalmological examination of the right eye, visual acuity remained at 10/10. Examination of the appendices showed conjunctival hyperemia localized nasally, axile exophthalmos, and painful limitation of abduction. The fundus examination was without abnormalities. Ophthalmological examination of the left eye was normal. The general examination did not show any associated extra-orbital clinical signs. Cranio-orbital MRI revealed myositis of the right medial rectus muscle. The etiological assessment (inflammatory, immunological and infectious) was negative. The thyroid assessment returned in favor of TRab negative hyperthyroidism. Thyroid ultrasound was normal. Thyroid scintigraphy showed homogeneous hyperuptake. The GO was treated with IV bolus corticosteroids then oral relay and a step down. After 4 weeks of monitoring, the evolution was favorable under treatment.

Conclusion: A minimal assessment should be considered in the event of any unilateral exophthalmos in order to exclude a tumoral, inflammatory process or lymphoma. However, GO must be considered in the face of any exophthalmos, and the thyroid assessment must be complete. Lymphoma can mimic GO, by infiltrating the oculomotor muscles, which may be its only manifestation. An orbital fixation in PET-CT points towards this etiology. Idiopathic intra-orbital inflammation syndrome remains the main differential diagnosis. In our patient, we retained the diagnosis of GD based on scintigraphy and hyper-FT4 evidence although the TRAbs were negative. These patients likely have low TRAb concentrations, which may be difficult to measure with current assay methods.