Fluctuating diplopia as an initial manifestation of polycythemia vera

Dear Editor:

Fluctuating diplopia as the sole initial manifestation of polycythaemia vera (PV) has never been described in the literature. We present the case of a woman diagnosed with PV who initially presented symptoms of fluctuating diplopia.

Clinical case

Our patient was a 60-year-old woman with a history of chronic migraine, atrial fibrillation, hypercholesterolaemia, and hyperuricaemia. She had undergone mitral valve replacement due to mitral insufficiency and was being treated with anticoagulants. For over a year, she had been experiencing approximately 3 episodes per month of binocular vertical diplopia lasting a few minutes and followed by instability and dizziness. She was simultaneously being examined by the haematology department for polycythaemia, which had been detected 4 months previously in a routine blood test. The general examination was normal; no adenopathies or organomegalies were identified. Baseline oxygen saturation was 99%. The neurological examination revealed left eyelid retraction but was otherwise normal. Eye movement, visual acuity, pupils, eye fundus, and visual field study results were normal. Brain and orbit MRI results were also normal; no pathological contrast enhancement was observed. The routine blood analysis showed a haemoglobin level of 19.1 g/dL, 60.5% haematocrit, 6.51 × 10⁶ red blood cells/μL, a mean corpuscular volume of 92.9 fL, 13.4 × 10³ white blood cells/μL, and 309 000 platelets/μL. These results were compatible with a myeloproliferative disorder. Erythropoietin levels were slightly decreased (2.28 mIU/mL); the rest of the iron profile and levels of vitamin B₁₂, folic acid, and alkaline phosphatase were normal. Abdominal ultrasound yielded normal results. A genetic study found a mutation in JAK2, which confirmed the diagnosis of PV. The patient underwent therapeutic phlebotomy and began treatment with hydroxycarbamide. In a follow-up consultation 6 months later, the patient showed improved blood test results and reported no new episodes of diplopia or dizziness.

Discussion

PV is a chronic myeloproliferative disorder affecting haematopoietic stem cells. It is characterised by excessive proliferation of red blood cells, white blood cells, and platelets. Criteria for diagnosis include hypercellularity, presence of splenomegaly, and mutation of the JAK2 gene.¹ It produces a variety of systemic complications with ophthalmologic manifestations, which are normally a consequence of hyperviscosity and thrombosis. They include cerebrovascular accidents, amaurosis fugax, monocular vision loss,² anterior ischaemic optic neuropathy,^3,4 retinal haemorrhages, and isolated cranial nerve palsy.⁵ Diplopia associated with PV has been linked to ischaemic events occurring in the brainstem at the level of the oculomotor nerve nuclei and pathway or in the nerves themselves. Anatomical differentiation is complex in many cases. In our patient, episodes of fluctuating diplopia were linked to microvascular lesions in the oculomotor nerves as a consequence of hyperviscosity. No further episodes have occurred since treatment was started and blood test results have returned to normal, meaning that the predisposing factor has been removed. Diplopia in the context of PV is rare. Ours is the first case of fluctuating diplopia reported in the literature. In-depth examination and cooperation with haematologists is essential in patients with diplopia in order to determine the appropriate treatment and avoid new ischaemic events.

Funding

The authors have received no funding for this study.

Conflicts of interest

The authors have no conflicts of interest to declare.