Borreliosis mimicking lupus‐like syndrome during infliximab treatment

Tumour necrosis factor (TNF)‐α antagonists are very effective treatments for immune‐mediated inflammatory disorders. Adverse events include severe infections and episodes of lupus‐like syndrome, multiple sclerosis‐like demyelination and other neuropathies. The pathomechanisms of these autoimmune‐like syndromes after TNF‐α blockade are still unknown. We report a patient with psoriasis who developed a lupus‐like syndrome during infliximab treatment, which was finally diagnosed as an exaggerated systemic infection with Borrelia burgdorferi. This case suggests that autoimmune‐like syndromes may actually represent pre‐existing or newly acquired nonseptic bacterial or viral infections, which have escaped immune surveillance during TNF‐α blockade. Each autoimmune‐like syndrome during TNF‐α blockade should therefore be carefully examined for potential causative infection.