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Title

A diagnostic challenge: Chronic myelomonocytic leukaemia and recurrent ischaemic optic neuropathy

Purpose	Ischaemic optic neuropathy (ION) is usually anterior and either arteritic (AAION), or non-arteritic (NAAION). Distinguishing between these two categories is not always simple, but crucial as they are associated with different underlying systemic conditions. Here we describe a rare and diagnostically challenging case and highlight the importance of diagnosis in atypical presentations.
Methods	A 66 year old Caucasian man presented with acute visual loss and a swollen right optic disc. He had risk factors and clinical features suggesting NAAION but a blood profile more consistent with an inflammatory process. He was started on steroids which were tapered after a negative temporal artery biopsy and symptomatic improvement. Over the next 5 months he suffered 2 more episodes of visual loss affecting both eyes. Re-introduction of steroids improved vision. Investigations revealed mildly raised inflammatory markers and thrombocytopenia. A rash was noted. Autoimmune tests showed a weakly positive ANCA. A raised white cell count was initially thought to be steroid induced, but further review showed an underlying monocytosis. A bone marrow biopsy demonstrated chronic myelomonocytic leukaemia (CMML). A skin biopsy revealed lymphocytic vasculitis.
Conclusion	We report for the first time ION linked to CMML and its associated vasculitis. We highlight the difficulty and delay in diagnosis due to the use of steroids masking an underlying systemic process. Recurrent ION and raised inflammatory markers should raise suspicion of vasculitis. Together with an elevated monocyte count, CMML should be considered.

Author 1

Last name	DE SMIT
Initials	E
Department	Eye Unit, Croydon University Hospital
City	London

Author 2

Last name	O'Sullivan
Initials	E
Department	Eye Unit, Croydon University Hospital