Chronic myelomonocytic leukaemia causing orbital inflammation.

We present a case of acute-onset orbital inflammation with rapidly progressive proptosis, episcleral venous stasis with raised intraocular pressure and loss of vision in a patient with a recent diagnosis of chronic myelomonocytic leukaemia (CMML). The patient's orbital inflammation and ocular hypertension showed no response to topical and systemic pressure-lowering agents and non-steroidal anti-inflammatory agents but resolved rapidly after the commencement of intravenous steroids. The patient was subsequently treated with the hypomethylating agent azacitidine with good systemic control of CMML with no further orbital inflammation. CMML is strongly associated with systemic inflammatory disease, possibly due to the upregulation of inflammatory pathways in the abnormal monocytes. CMML is a rare cause of orbital or ocular inflammation but should be considered in patients with persistent monocytosis.