Mild Thyroid Eye Disease—The Most Common yet the Least Studied Presentation of Thyroid Eye Disease

BACKGROUND: Mild thyroid eye disease (TED) is the most common form of TED, yet it is the least studied. Uncertainties about the natural history and prevention, and underfunding for clinical research, are an obstacle to improving the management of this important group of patients. SUMMARY: The available evidence suggests that the prevalence of mild TED can reach up to two-thirds of all cases, depending on the expertise of the assessor and the criteria used for diagnosis. Prevalent symptoms and signs of mild TED predominantly arise from lid changes, soft tissue involvement and ocular surface disease, but disease presentation is heterogeneous and in some patients proptosis and eye motility changes may be underrated with the current classification. Little is known about the impact of the various manifestations of mild disease on patients' risk of progression and quality of life (QoL). Although in most patients with mild TED the disease remits spontaneously, some patients progress, and a significant proportion evolve to persistent, inactive TED. Current therapeutic options for these patients are based on scarce, low-to-moderate quality and sometimes conflicting evidence, resulting in significant differences in the management of mild TED in different countries and by different specialists. Among the most recommended therapeutic interventions, selenium supplementation was mainly studied in selenium-insufficient populations with active mild TED and it lacks efficacy in longstanding, inactive disease. The use of immunosuppressive drugs and targeted therapies for mild TED are commonly reported by surveys of medical professionals in a clinical setting, but the indication and efficacy of these agents in mild TED remain unclear. CONCLUSIONS: Mild TED has a significant psychosocial and functional burden that should be reconsidered and addressed by local, systemic or surgical treatments in an individualized manner. Given the overall effect on QoL and the socioeconomic impact, it is of immediate importance to highlight the knowledge gaps and the need for research in mild TED.