This NI study will enroll 150 patients from approximately 15 sites across the US. The study population eligible for enrollment includes adult and adolescent patients aged ≥12 years diagnosed with moderate to severe AD who receive at least one dose of abrocitinib and satisfy the inclusion and exclusion criteria. Patients who had inadequate response or intolerance to previous ≤2 biologic therapies will be included in this study as there is a lack of effectiveness data for abrocitinib in these patients. As this will be an observational study, there will be no sampling and all patients that meet the inclusion and exclusion criteria will be recruited consequently. The study will be open for enrollment for approximately 12 months after the first patient has been enrolled. Regarding the inclusion and exclusion criteria, in the real-world setting recruitment may be slower than expected, thus depending on the observed enrollment rate, the enrollment period and number of sites may be reassessed and revised during the study.

9.2.1. Inclusion Criteria

Patients must meet all of the following inclusion criteria to be eligible for inclusion in the study:

1. Participants who have chronic AD that has been present for ≥1 year before screening.
2. Male and female patients aged >12 years at baseline.
3. Patients with diagnosis of moderate-to-severe atopic dermatitis confirmed by a certified dermatologist, who are prescribed abrocitinib for use in accordance with the product label (USPI) and independently of the decision to enroll the patient in this study
4. Patients who have inadequate responses or are intolerant to ≤2 previous biologic therapy approved for M2S AD. (Patients shall have had an inadequate response and/or intolerance to at least one, but no more than 2 biologic therapies approved for moderate-to-severe AD)
5. Evidence of a personally signed and dated informed consent document indicating that the patient (or a legally acceptable representative) has been informed of all pertinent aspects of the study. Following receipt of oral and written information about the study, the adolescent (depending on local institutional review board/independent ethics committee requirements) must provide assent, and one or both (according to local regulations) parents or guardians of the child must provide signed informed consent before any study-related activity is carried out.
6. Patients, who in the opinion of the investigator, are willing and able to comply with regular clinic visits as per standard practice at the site and agree to complete PRO questionnaires and other patient completed questions.

9.2.2. Exclusion Criteria

Patients meeting any of the following criteria will not be included in the study:

1. Patients, that currently have active forms of other inflammatory skin diseases, other than AD or have evidence of skin conditions (eg, psoriasis, seborrheic dermatitis, Lupus) at the time of Day 1 that would interfere with evaluation of atopic dermatitis or response to treatment.
2. Patients previously treated with abrocitinib or other oral/systemic JAK inhibitors
3. Investigator site staff or Pfizer employees directly involved in the conduct of the study, site staff otherwise supervised by the investigator, and their respective family.
4. Patient eligibility should be reviewed, documented, and confirmed by an appropriately qualified member of the investigator's study team before patients are enrolled in the study.

History of severe allergic reactions to study medication Currently pregnant or breastfeeding Recent participation in another clinical trial within the last 30 days Presence of uncontrolled medical conditions that could affect safety