Bilateral vision loss at high altitude: A diagnostic dilemma

A young male patient of 22 years inducted at 11,000 feet altitude presented with a sudden onset bilateral diminution of vision associated with easy fatiguability and generalised weakness. Fundus examination revealed preretinal haemorrhages and Roth spots both eyes, owing to which differential diagnosis of high altitude retinopathy (HAR) and haematological disorders was considered. On systemic examination, he had pallor with massive splenomegaly. Haematological investigation revealed high total leucocyte count (TLC) 2.96 lac (normal 4000-11,000/uL) with peripheral blood smear showing increase in basophils, neutrophil precursors, myelocyte bulge, anaemia with no blasts suggestive of chronic myeloid leukaemia-chronic phase. Hence, a diagnosis of chronic myeloid leukaemia (chronic phase) with no features of tumour lysis syndrome was made. Patient was started on Tab hydroxyurea 50 mg twice a daily and managed by haemato-oncologist and required no further active ophthalmological intervention.