The PGA is a 5-point scale ranging from 0 (clear), 1 (almost clear), 2 (mild), 3 (moderate), to 4 (severe), incorporating an assessment of the severity of the Plaque-Psoriasis.

BSA is a measurement of involved skin. The overall BSA affected by psoriasis is estimated based on the palm area of the participant's hand (entire palmer surface or "handprint" excluding DIPs), which equates to approximately 1% of total body surface area.

Psoriasis Area Severity Index (PASI) scores range from 0 to 72, with higher scores reflecting greater disease severity. Erythema, thickness, and scaling are scored on a scale of 0 (none) to 4 (very severe) on 4 anatomic regions of the body: head, trunk, upper limbs, and lower limbs. Degree of involvement on each of the 4 anatomic regions is scored on a scale of 0 (no involvement) to 6 (90% to 100% involvement). The total qualitative score (sum of erythema, thickness, and scaling scores) is multiplied by the degree of involvement for each anatomic region and then multiplied by a constant. These values for each anatomic region are summed to yield the PASI score.

The PaGA is a 5-point scale ranging from 0 (clear), 1 (almost clear), 2 (mild), 3 (moderate), to 4 (severe), incorporating an assessment of the severity of the Plaque-Psoriasis by the patient.

PPQ is a questionnaire consisting of 5 questions. PPQ asks the patient for his preference of the actual therapy versus the previous systemic therapy.

STAQ; patient questionnaire on patient benefit, communication physician/patient, patient knowledge, and treatment satisfaction with the current systemic treatment (38 questions).

The Pain Visual Analog Scores (VAS) is used to measure the amount of pain a participant experiences. Participants are asked: How much pain do you actually experience? All VAS values range from 0 to 100. Higher scores correspond to more severe symptom or disease.

All Serious Adverse Events (SAEs), irrespective of relationship to Apremilast, and all non-serious AEs considered at least possibly related to Apremilast administration [non-serious adverse drug reactions (NS ADRs)], must be recorded within 24 hours of the physician's knowledge to the Sponsors' Drug Safety Department. AEs will be reported by the sponsor as required to Regulatory Authorities and Ethics Committees as applicable, in accordance with the national requirements for marketing authorization holders.

The Itch Visual Analog Scores (VAS) is used to measure the amount of itch a participant experiences. Participants are asked: How much itch do you actually experience? All VAS values range from 0 to 100. Higher scores correspond to more severe symptom or disease.

PGA: 5-point scale for the physician's global assessment of the severity of scalp psoriasis.

PaGA: 5-point scale for the patient's global assessment of the severity of scalp psoriasis.

NAPSI: Assessment of target fingernail for nail bed and nail matrix involvement, each can be scored 0-4. Total score ranges from 0-8.

Fingernail Patient Global Assessment ; 5-point scale on the patient's global assessment of the fingernail involvement, substituted with a 0-100 Visual analog scale (VAS) for the assessment of the impairment caused by this nail involvement.

PGA: 5-point scale for the physician's global assessment of the severity of palmoplantar involvement.

PaGA: 5-point scale for the patient's global assessment of the severity of palmoplantar involvement.