A 25 yo woman with Hashimoto’s thyroiditis presented to her PCP for facial weakness. She was treated for “Bell’s palsy” with Prednisone. Symptoms improved for a month but again worsened, with accompanying dysphagia and nasal speech. AChR antibodies were negative. MRI brain only showed an incidental arachnoid cyst adjacent to CN V-3. She was referred to ENT, rehab, and eventually cognitive behavioral therapy for “conversion disorder”. She returned in 3 months with facial weakness and pain, diagnosed as sinusitis, and again received steroids. Repeat AChR and MuSK Abs were negative. TPO Abs were elevated.

She was referred to neurology a few months later. Exam revealed fatigable weakness of the faciobulbar and proximal muscles. Repetitive nerve stimulation showed pathologic decremental responses. While repeat labs were pending, she had a positive response to Pyridostigmine and was started on IVIg and Prednisone. Repeat labs returned positive AChR Abs by live cell-based assay, a repeat routine AChR Ab RIA titer just above the cutoff (0.5 nmol/L, normal up to 0.4), as well as positive LRP4 Abs. CT chest showed normal thymus for age. She will likely be started on Efgartigimod as well as undergo thymectomy.