Psoriasis in children — formative SAQs

SAQ 1 (10 marks)

A 12-year-old girl has a three-year history of chronic plaque psoriasis affecting the elbows, knees, scalp and lower back, with nail pitting and onycholysis. Topical calcipotriol with a potent corticosteroid and two courses of narrowband UVB phototherapy have produced only transient improvement, her body surface area involvement is around twenty per cent, and her Children's Dermatology Life Quality Index is 16. She is overweight, and she has recently described early-morning knee stiffness lasting forty minutes. ^[1]

Question: Outline your assessment, the stepwise systemic therapy options, and how you would decide whether to start a biologic agent. Address the comorbidity that the morning stiffness raises. (10 marks) ^[1]

Model answer

Assessment and severity (2 marks). This is moderate to severe plaque psoriasis refractory to optimised topical therapy and phototherapy, with a substantial quality-of-life impact (CDLQI 16) and around twenty per cent body surface area involvement. Confirm the diagnosis clinically, re-measure severity with body surface area and a physician global assessment or PASI, and capture quality of life. She has failed conventional first- and second-line therapy, which is the trigger to consider systemic therapy. ^{[1] [2]}

Systemic therapy options (3 marks). The first conventional systemic choice is methotrexate, given once weekly at approximately 0.1 to 0.4 mg/kg/week up to about 25 mg/week, oral or subcutaneous, with folic acid supplementation and monitoring of full blood count and liver function. Cyclosporin offers rapid short-course control for a child needing stabilisation, with blood pressure and renal monitoring, before transition to a maintenance agent. Acitretin is an option for pustular or palmoplantar patterns but is strongly teratogenic, so in an adolescent girl of childbearing potential it is avoided or used only with rigorous contraception. The choice is a shared decision weighing efficacy, monitoring burden and the individual risk profile. ^{[1] [2]}

The biologic decision (3 marks). A biologic is considered for severe, refractory disease or where conventional systemic therapy fails or is unsuitable, after a baseline infectious-disease screen including tuberculosis, hepatitis B and C and (where relevant) HIV. The landmark paediatric etanercept trial — subcutaneous etanercept 0.8 mg/kg weekly — established the evidence base, and ustekinumab (blocking IL-12 and IL-23) and the IL-17 inhibitors secukinumab and ixekizumab extend the options, with several agents now having age-specific paediatric approvals. The recent biologics network meta-analysis ranks the classes by efficacy and tolerability, and the choice is guided by severity, comorbidity, prior therapy and the skin and joint involvement. Because she has joint symptoms, an agent active in both skin and joint disease (such as a TNF-alpha or IL-17 or IL-23 inhibitor) may be preferred. ^{[9] [10]}

The comorbidity — juvenile psoriatic arthritis (2 marks). Early-morning knee stiffness lasting forty minutes in a child with psoriasis and nail disease signals juvenile psoriatic arthritis, which can precede or accompany skin disease and risks permanent joint damage and uveitis. Refer early to paediatric rheumatology, screen for uveitis as guided by the rheumatology team, and coordinate dermatology-rheumatology care. The joint symptoms and the obesity both reinforce the point that psoriasis in a child is a multisystem disease whose whole-child assessment — weight, joints and mood — is as important as the skin. ^{[1] [11]}