Psoriasis Associated with Interferon Beˆta-1b in a Multiple Sclerosis Patient with Positive Rechallenge

Introduction: Several drugs such as lithium, beta-blockers, adrenergic antagonists, and interferons can aggravate pre-existing psoriasis or cause de novo psoriasis. Few cases of psoriasis were described with interferon beta-1b. Objective: Herein we report a rare case of interferon beta-1b induced nummular psoriasis that occurred in a multiple sclerosis patient with positive rechallenge. Methods: This case was reported in August 2020 and evaluated according to the French imputation method of causality assessment. Results: A 39-year-old woman with no medical history of skin diseases has started interferon beta-1b for her multiple sclerosis. After one month of daily use, she presented a generalized erythroderma and secondary diffuse erythemato-squamous coin-sized lesions evocative of nummular psoriasis. The patient denied any recent infection or stress. The evolution was favorable 20 days after drug withdrawal with corticosteroids treatment. After full recovery the rechallenge was attempted and the same symptomatology recurred one month later after the onset. Conclusion: We suspected that interferon was the causative agent in the induction of psoriasis. The imputation score was likely due to the evocative delay of psoriasis occurrence, the favorable outcome after drug withdrawal, and the positive rechallenge. Activation of psoriasis is an uncommon side effect of drugs and could mimic other cutaneous diseases in its rare features [1]. Physicians taking care of sclerosis patients should be aware of this affection which need careful evaluation of an added morbidity.