Case Presentation: 54-year-old male with history of stroke, seizures, neurogenic bladder, and spine surgery presented with increasing left sided weakness, trouble swallowing, unintentional 67-pound weight loss, headaches and double vision. On exam, he had bilateral upper extremity weakness, partial ptosis, diplopia, right eye ocular palsy, right eye gaze restriction in supraduction and abduction. Complete blood count and metabolic panel were unremarkable, including HIV and hepatitis panel. CT chest was negative for thymoma. CT head, CTA head and neck showed no evidence of vascular injury or CVA. MRI brain had no acute findings. Serum Acetylcholine Receptor Antibody was positive. A diagnosis of Myasthenia Gravis was made, pyridostigmine and IVIG were initiated. Monocular eye patching for diplopia relief was initiated. While receiving treatment for MG, he complained of severe retro orbital headaches. He did not have jaw claudication or blurry vision. On exam he had right temporal region tenderness and his ESR and CRP were elevated which raised suspicion for giant cell arteritis. A temporal artery ultrasound showed bilateral halo sign. He received high dose prednisone 80 mg for GCA, given the ultrasound findings. 2 days later, he had worsening respiratory muscle and extremity weakness, so steroids were stopped, after which his muscle weakness improved. His headache persisted but was slightly better. Temporal artery biopsy showed no evidence of arteritis or giant cells. His repeat ESR and CRP continued to be elevated. He was restarted on low dose prednisone at 10 mg for GCA. His headache and MG symptoms improved, and he was discharged with pyridostigmine.
Discussion: This case is unique as there are few cases of MG and GCA occurring at the same time and management can be challenging. There is a 9-18% risk of precipitating MG with the use of steroids via a mechanism that is not well understood. Thus, it is critical to clarify the diagnosis of GCA before starting treatment. While temporal artery biopsy is the gold standard for GCA diagnosis according to the ACR/VF 2021 guidelines, emerging data has found that the ultrasound halo sign may be used to diagnose GCA, especially with consistent history and physical. The halo sign has a 77% sensitivity and 96% specificity, and bilateral halo sign increases its specificity to nearly 100%. Bilateral halo sign supports GCA diagnosis, but lack of it may not rule it out. Meanwhile, temporal artery biopsy has sensitivity of 77% and specificity of 100% for GCA diagnosis with a false negative rate of 9-61%. Since hospitalization, he completed the first cycle of Efgartigimod alfa and his eye symptoms, weakness and balance has improved. He was started on Tocilizumab for his GCA with PJP prophylaxis.
Conclusions: This patient had a rare combination of autoimmune disease that was identified and treated, but it was challenging given the effect of high dose steroids on MG. His temporal artery biopsy was negative but his bilateral halo sign and supporting history was sufficient for diagnosis of GCA. Patients with MG should be monitored when being treated with high dose steroids as they can precipitate myasthenic crisis. Learning Objectives 1. Bilateral halo sign is more specific than temporal artery biopsy and is sufficient for diagnosis of GCA. 2. Steroids can precipitate MG, so their use should be monitored and administered at low doses, with steroid sparing agents preferred. 3. Providers should be open minded when clinical findings warrant coexisting autoimmune diseases.