Abstract We describe a 26-year-old man treated with azathioprine for myasthenia gravis who developed acute left-sided peripheral facial weakness. Brain magnetic resonance imaging (MRI) revealed enhancement in the left geniculate ganglion and in the intracanalicular and tympanic segments of the facial nerve. Analysis of cerebrospinal fluid (CSF) and serum revealed intrathecal synthesis of anti-varicella zoster virus (VZV) IgG antibody. Although previous analyses of saliva, blood mononuclear cells, serum antibodies, middle ear fluid, and auricular and geniculate zone skin scrapings have shown that a small but definite proportion of patients with idiopathic peripheral facial palsy (“Bell's palsy”) have the Ramsay Hunt syndrome zoster sine herpete (RHS ZSH), this is the first confirmation of RHS ZSH by intrathecal synthesis of anti-VZV IgG antibody. In addition, herpes simplex virus (HSV)-1 DNA was found in saliva of the patient on 3 consecutive days. Simultaneous reactivation of two alphaherpesviruses (HSV-1 and VZV) in our immunosuppressed patient underscores the need to consider opportunistic infection as a cause of facial weakness.