Sir,

We describe a patient with signs of partial third nerve palsy, severe iritis, and loss of vision due to essential thrombocytosis.

Case report

A 60-year-old man was referred from the neurologists by whom he had previously been treated under suspicion of TIAs.

Initially, visual acuity was 6/6 in both eyes. At presentation, a ptosis on the left eye was observed, but otherwise the eye examination was unremarkable. After a couple of months, he developed several episodes of aggressive iritis, with various forms of keratic precipitates. He had posterior synechiae and markedly increased intraocular pressure (IOP). He had no corneal oedema, pain, or photophobia. Uveitis investigation and MRI of the orbits were normal.

At that time, repeated blood tests showed an elevated platelet count (∼80 × 10/l). A bone marrow biopsy was performed and essential thrombocytosis was diagnosed.

He was continuously treated with hydroxyurea as well as venesection and the iritis is more readily controlled—but vision has slowly deteriorated. Two years after diagnosis, vision is now restricted to counting fingers with a pale optic disc on fundoscopy. No retinal changes have been observed, and no neovascularisations have been seen on the iris. The ptosis is unresolved and eye movements are normal.

Essential thrombocytosis causes multiple vascular occlusive disease and some groups have reported vascular retinal occlusions in essential thrombocytosis.1, 2 To our knowledge, iritis has never been reported in essential thrombocytosis, and only one previous report has described a partial third nerve palsy in essential thrombocytosis.3

Comment

As essential thrombocytosis is not a leukaemic or carcinoid disease, it is unlikely that iritis is due to an autoimmune reaction, but more so due to an ischaemic reaction. Cells in the anterior chamber have been described in ocular ischaemic syndrome.4 The patient also suffered from an unspecific constant burning periocular pain—possibly of ischaemic origin.

It is concluded that the patient, because of essential thrombocytosis, suffered from multiple minor ischaemic events in the central nervous system, including a partial third nerve palsy and severe ocular ischaemia, which has caused iritis and slow progressive optic neuropathy.