A flare-up of pemphigus vulgaris lesions indicates that your current doses of methylprednisolone (14 mg) and azathioprine (50 mg) are no longer sufficient to control the autoimmune response. Please do not adjust your medication dosages on your own, as improper adjustments can worsen the condition or cause severe side effects. You must contact your dermatologist immediately. They will likely need to temporarily increase your methylprednisolone dose to control the active blistering and may evaluate whether to adjust your azathioprine dose or introduce other treatments, such as rituximab. Prompt clinical evaluation is essential to prevent widespread lesions and potential infections.