Efalizumab is a monoclonal a humanized recombinant IgG1 monoclonal antibody which targets the CD11a, the alpha-subunit of LFA-1 (lymphocyte function-associated antigen-1). It acts by blocking the T-lymphocyte pathogenetic mechanisms of psoriasis. Thrombocytopenia is an adverse event that occurs during therapy. Thrombocytopenia can be mild and can occur quite early during treatment, together with leukocytosis. Both adverse events tend to normalize with ongoing therapy, or, in cases worsening, with therapy suspension. There have been multiple reports of thrombocytopenia associated with efalizumab therapy for the treatment of psoriasis. The general recommendation is to check platelet counts monthly for the first 3 months of efalizumab therapy, then every 3 months for the duration of therapy. According to our experience on a wide range of patients, it is useful to check platelets every month for the first 6 months of therapy. We report a case of efalizumab-associated thrombocytopenia that occurred after 16 weeks of therapy together with clinical worsening of skin lesions. The peculiarity of our case is the absence of signs and symptoms linked to thrombocytopenia and the quick return to normal platelet count without corticosteroid therapy
