Multiple halo naevi associated with tocilizumab

Tocilizumab, a humanized monoclonal antibody directed against the interleukin (IL)-6 receptor, is approved for the treatment of rheumatoid arthritis and juvenile idiopathic arthritis (JIA). We describe a case of multiple halo naevi occurring in a patient with a history of JIA treated with tocilizumab. IL-6 is a key cytokine in the setting of cancer through its effects on angiogenesis and inhibition of adaptive anti-tumour immunity. IL-6 also plays a role in melanocyte function, and increased levels have been noted in vitiligo skin, where it is a paracrine inhibitor of melanocytes. Tocilizumab may therefore lead to the development of halo naevi secondary to subsequent activation of adaptive immunity. Alternatively, as tocilizumab results in increased serum IL-6 levels, the epidermal cytokine profile is altered. Increased levels of IL-6 may therefore have a direct inhibitory effect on melanocytes, where access by tocilizumab may be limited due to differential size difference.