Onset of palmoplantar pustular psoriasis while on adalimumab for psoriatic arthritis: a 'class effect' of TNF-alpha antagonists or simply an anti-psoriatic treatment adverse reaction?

Adalimumab is a human, recombinant IgG1 monoclonal antibody that specifically blocks the interaction of tumour necrosis factor (TNF)-alpha with the p55 and the p75 TNF-alpha cell surface receptors. We report the appearance of palmoplantar pustular psoriasis in a patient after 6 months of successful adalimumab administration for psoriatic arthritis. The development or worsening of psoriatic skin lesions is a known side effect of adalimumab and other TNF-alpha antagonists increasingly reported in the literature. Although it has been reported as a 'class-effect' of TNF-alpha antagonists, we believe that the deterioration or new onset of psoriasis is an adverse reaction seen mainly with drugs used for the treatment of psoriasis and not solely with anti-TNF agents. The latter is probably implying an existing gap in the understanding of the pathophysiology of psoriasis or of the anti-psoriatic drugs' mechanisms of action.