Is leflunomide effective in the treatment of psoriasis in a patient who is unable to benefit from standard first- and second-line therapies and needs an affordable treatment option?

A 21-year-old man was seen for a 4-year history of recalcitrant, severe psoriasis. The problem affected the patient’s quality of life significantly, especially in having to miss lectures at college. Many treatments had been tried. He had been admitted to the hospital 4 times and was a regular attendee at the day treatment unit. Topical coal tar and anthralin caused irritation. Acitretin therapy (0.5 mg/kg) was ineffective. Therapy with oral or intramuscular methotrexate caused intolerable nausea. Systemic psoralen–UV-A and narrowband UV-B caused repeated erythema and were therefore stopped. Cyclosporin therapy caused acute renal impairment. Leflunomide is a disease-modifying antirheumatic drug recently licensed for psoriatic arthritis, for which it has both shortand long-term benefit, and it has some possible benefit for psoriasis. It is a pyrimidine synthesis inhibitor and prevents lymphocyte proliferation, especially T cells. The aim of this Critically Appraised Topic is to determine from the available evidence whether oral leflunomide would be an effective and affordable treatment option for our patient’s psoriasis.