Delayed Diagnosis of Essential Thrombocythemia due to a History of Iron Deficiency Anaemia and JAK2 Negativity in an Air Hostess : A Case Report and Literature Review

Abstract

Essential thrombocythemia (ET) is a myeloproliferative neoplasm that may present asymptomatically with isolated thrombocytosis. This often contributes to delayed diagnosis, particularly in the presence of potential secondary causes such as iron deficiency anemia. We report the case of a 39-year-old female airline cabin crew member under follow-up at a flight crew medical assessment center. She had a history of treated iron deficiency anemia and was noted to have a platelet count of 650,000/mm³ during a routine review in October 2020. She remained asymptomatic, and her clinical examination was unremarkable, with no prior history of arterial or venous thrombosis. Initial diagnostic work-up was limited to testing for the JAK2 mutation, which was negative, reinforcing the suspicion of reactive thrombocytosis secondary to anemia. However, in October 2024, the emergence of extreme thrombocytosis prompted further molecular evaluation, which revealed a positive calreticulin (CALR) mutation, confirming the diagnosis of essential thrombocythemia. Despite stringent and routine health monitoring of aviation personnel, this case highlights how diagnostic delays can occur due to limited access to comprehensive molecular testing, cost constraints associated with Next-Generation Sequencing (NGS) panels, and misleading secondary findings such as anemia. The patient is now under regular surveillance by both her hematologist and the aviation medical specialist, as per the decision of the aviation medical expert committee, to ensure medical stability during flights. This is essential to avoid any in-flight health emergencies that could lead to complications for cabine crew and to aircraft diversion and consequent financial implications for the airline.