Inclusion Criteria:

• * Males or females with DS between 12 and 50 years of age who weigh at least 40 kg.
• * Diagnosis of at least one active immune skin condition, including but not limited to:
• 1. Moderate-to-severe atopic dermatitis
• 2. Alopecia areata affecting at least 25% of the scalp
• 3. Moderate-to-severe hidradenitis suppurativa
• 4. Moderate-to-severe psoriasis
• 5. Moderate-to-severe vitiligo.
• * Be willing to avoid pregnancy or fathering children.
• * Must present with a study partner or legal guardian who can complete, or assist with completing, study materials as appropriate.
• Exclusion Criteria
• * Weigh less than 40 kg.
• * Pregnancy or breast feeding.
• * No study partner or legal guardian.
• * Vaccination with live attenuated virus within six weeks of inclusion in the study or planned during the study.
• * Clinically significant chronic or active viral infection including but not limited to HIV, hepatitis, CMV, EBV, HSV.
• * Severe renal impairment.
• * History of malignant solid tumor cancer within five years prior to study entry or where there is current evidence of recurrent or metastatic disease.
• * Poor venous access not allowing repeated blood tests or non-compliance with venipuncture requirements.
• * Prior treatment with a JAK inhibitor or with an investigational agent, device, or procedure within 21 days of enrollment.
• * Concomitant treatment with other immunosuppressants (e.g. corticosteroids, methotrexate) or strong CP3A4 or CYP2C19 inhibitors or inducers (e.g. ketoconazole, fluconazole).
• * Known allergies, hypersensitivity, or intolerance to Tofacitinib.
• * History of thrombotic disorder.
• * Superficial skin infection within 2 weeks of inclusion in the study.
• * History of disseminated herpes zoster, disseminated herpes simplex, or recurrent localized dermatomal herpes zoster.
• * Intravenous antimicrobial therapy within 3 months of inclusion in the study.
• * Oral antimicrobials within 2 weeks of inclusion in the study.
• * Participants may be excluded for other unforeseen reasons at the study doctor's discretion.
• * Unable to provide assent in cases where informed consent is obtained from other authorized representative.
• * Kidney transplant within the last two years
• * Any history of heart attack or stroke.
• * Any history of lymphoma.
• * Past or current smokers.