Janus Kinase Inhibition in Granuloma Annulare

Inclusion Criteria: * Written informed consent * Male and female patients 18 years old or older * Diagnosis of GA with supportive skin biopsy * BSA involvement of at least 5% * If patients are on systemic therapies or phototherapy for their GA, they must discontinue these therapies with a washout period of 4 weeks and must remain off them during the study * If patients are on topical therapies for their GA, they must discontinue these therapies with a washout period of 2 weeks and must remain off them during the study * Females of childbearing potential must agree to use birth control during the study and there must be a negative pregnancy test documented prior to starting the medication. * Patients must be willing to have skin biopsies, blood collection, and total body photography and to comply with clinic visits Exclusion Criteria: * Age \<18 years old * Patients with a history of malignancy (except history of successfully treated basal cell or squamous cell carcinoma of the skin) * Patients known to be HIV or hepatitis B or C positive, or have an active, serious infection herpes simplex, herpes zoster, and pneumonia. This would also include localized infections. * Patients with positive tuberculin skin test or positive QuantiFERON® Tuberculosis test * Patients with significant hepatic impairment * Patients with moderate renal impairment * Patients with uncontrolled peptic ulcer disease * Patients with a history of deep vein thrombosis and/or pulmonary embolism and/or clotting disorder * Patients with any history of myocardial infarction or stroke. * Patients taking concomitant immunosuppressive medications, with the exception of methotrexate and/or low-dose prednisone, including but not limited to mycophenolate mofetil, azathioprine, tacrolimus, cyclosporine, or TNF-α inhibitors * Women of childbearing potential who are unable or unwilling to use birth control while taking the medication * Women who are pregnant or nursing * Current smoker or history of any tobacco use * Screening labs outside the normal range for parameters associated with potential risk for treatment under investigation. Including but not limited to: i. Platelets \<150,000/mm3 ii. Absolute neutrophil count \<1,000/mm3 iii. Hemoglobin levels \<8 g/dL iv. Absolute lymphocyte count \<500/mm3 * Patients who are taking moderate to strong inhibitors of both CYP2C19 and CYP2C9, or strong CYP2C19 or CYP2C9 inducers, as well as P-gp substrate where small concentration changes may lead to serious or life-threatening toxicities. * Patients who have received a live vaccine. Patients should wait a minimum of 2 weeks, if recently vaccinated, prior to initiating treatment and should not receive a live vaccine during treatment or 2 weeks post-treatment. * Patients with any medical, psychiatric, or social condition that is likely to unfavorably affect the risk-benefit of continued study participation, interfere with study compliance or confound safety or efficacy assessments