A diagnostic challenge: chronic myelomonocytic leukaemia and recurrent anterior ischaemic optic neuropathy.

We report the first case of ischaemic optic neuropathy (ION) linked to chronic myelomonocytic leukaemia (CMML) and its associated vasculitis. We discuss the link between CMML and vasculitis and the evidence suggesting it can cause anterior ischaemic optic neuropathy through a vasculitic process. We highlight the difficulty and delay in diagnosis as the use of steroids masked an underlying systemic process. Recurrent ION and raised inflammatory markers should raise suspicion of vasculitis. Together with an elevated monocyte but low platelet count, CMML should be considered.