‣ All subjects:

• Subject is willing to participate and is capable of giving informed consent. Note: Consent must be obtained prior to any study-related procedures.

• Subject must be willing to comply with all study procedures and must be available for the duration of the study.

• Healthy volunteers:

• Male or female subject aged 18 years or older, at the time of consent.

• Subject is in good general health, according to the investigator's judgment.

• Subjects with Acne:

• Male or female subject aged 18 to 45 years old, inclusive, at the time of consent.

• Subjects with AD:

• Male or female subject aged 18 years or older, at the time of consent.

• Subject has clinically confirmed diagnosis of active AD, according to Hanifin and Rajka criteria.

• Subjects with CHE:

• Male or female subject aged 18 years or older, at the time of consent.

• Subject has at least a 6-month history of CHE before Screening (information obtained from medical chart or subject's physician, or directly from the subject).

• Subjects with HS:

⁃ Male or female subject aged 18 years or older, at the time of consent.

⁃ Subject has a clinically confirmed diagnosis of active HS with a disease duration of ≥ 6 months before screening as determined by the investigator through subject interview and/or review of the medical history.

⁃ Subjects with PPP:

⁃ Male or female subject aged 18 years or older at the time of consent.

⁃ Subject has at least a 6-month history of PPP as defined by the presence of pustules on palms and/or soles, but without evidence of infection on palms and soles (information obtained from medical chart or subject's physician, or directly from the subject).

⁃ Subjects with psoriasis:

⁃ Male or female subject aged 18 years or older, at the time of consent.