Endocrine Abstracts

Myasthenia gravis (MG) and Graves’ ophthalmopathy (GO) share many clinical characteristics but may also co-exist. Both are autoimmune disorders mediated by organ specific pathogenic autoantibodies to membrane surface receptors. Differential diagnosis and/or co-existence provides a potential management challenge, and there is a paucity of demographic information regarding precise prevalence rates and concurrence of disease.

Method: Retrospective chart review from a single institution registered as a Quality Improvement project. Demographic data were cross-referenced from the comprehensive Myasthenia Gravis database and Graves’ Ophthalmopathy databases to identify dual diagnoses.

Results: 858 patients were identified with MG and 270 patients GO. Five patients had both MG and GO. Thus, in MG, prevalence of GO was 0.58% and prevalence of MG in GO patients was 1.9%. The predominant diagnosis was MG in all 5 patients. Four of the five patients initially presented with ocular myasthenia (80%). One patient, initially diagnosed with generalised MG, subsequently developed ocular symptoms. Acetylcholine receptor antibodies were positive in all patients, with a mean level of 156 (range 6-514). Mean age of primary diagnosis of MG was 49 years (range 30-76 years). There was a slight female predilection (40% male, 60% female). Concurrent thyroid dysfunction was diagnosed incidentally, on biochemical screening, in all patients. TSH receptor antibodies were elevated in 4 patients where available (mean 1.68 (range 0.5-3.2). All patients were treated initially with pyridostigmine. One patient required rituximab/methyprednisolone combination treatment for active thyroid eye disease with extra ocular muscle enlargement on MRI imaging.

Conclusion: Coexisting pathology is not uncommon, and important to consider when managing patients where presentation is perhaps less typical with either condition. Imaging is helpful as appearances of GO are distinctive. TFT and possibly TRAb should be considered in all patients with ocular MG. The potential for steroid sparing co-management with Rituximab needs further research.