Abstract
Background/Aims
The ocular manifestations of giant cell arteritis (GCA) and ocular myasthenia gravis (OMG) have significant overlap, which can lead to clinical uncertainty in the absence of awareness and routine diagnostic testing.
Methods
We present the case of a 63-year-old male patient with a strong family history of autoimmune disease. He presented to the Rheumatology department in 2009 with symptoms of polymyalgia rheumatica (PMR) and was treated successfully with a reducing regime of Prednisolone. In 2013, he presented to the Ophthalmology department with blurred vision and diplopia. Giant cell arteritis was suspected and a high dose of Prednisolone was started. His temporal artery biopsy was normal and inflammatory markers were not raised, but there was a complete resolution of his symptoms since starting steroids. Under the care of the Rheumatology department, reducing regimes of Prednisolone were attempted and a steroid sparing agent, Methotrexate was introduced. Unfortunately, he continued to have recurring symptoms of blurred vision and diplopia, particularly at Prednisolone doses less than 20mg. Over the course of a few years, there was a progression of his ocular symptoms. He developed a horizontal diplopia, monocular ptosis and a 4th nerve palsy. He was referred back to the Ophthalmology department, where alternate diagnoses were investigated. Anti-acetylcholine receptor antibodies (AChR) were strongly positive at 35 mU/L (normal <0.44 mU/L). MRI head was normal, and CT chest showed no thymoma. Single fibre EMG confirmed severe OMG. Our patient was subsequently commenced on Pyridostigmine, with which symptoms improved.
Results
The literature on OMG mimicking GCA is sparse. The prevalence of an exclusively ophthalmic presentation in patients with GCA is 1 in 5. Ocular signs and symptoms in GCA can vary drastically due to the propensity of the disease to affect different structures within the eye. Transient and permanent visual loss, affects 10-30% of GCA patients due to anterior ischemic optic neuropathy. Diplopia affects 5% of GCA patients. In comparison, OMG can be the only presenting feature in 15% of patients with Myasthenia Gravis, and is characterised by unilateral ptosis, oculomotor paresis and binocular diplopia.
Conclusion
This case highlights the clinical similarities of OMG and GCA, and that OMG should be considered as a differential diagnosis when the clinical picture of GCA does not truly fit. In patients presenting with GCA with ocular symptoms, normal inflammatory markers and no systemic features, OMG should be considered and AChR antibody testing be performed. More awareness of OMG is needed. We also propose that OMG should be included as a differential diagnosis, in the British Society of Rheumatology guidelines for GCA.
Disclosure
A. Gharatya: None. J. Wajed: None. N. Cernovschi: None. D. Christidis: None.
Myasthenia Gravis and Stroke in the Setting of Giant Cell Arteritis