A case of a 22-month-old boy with necrotizing pneumonia presenting with leukaemoid reaction misdiagnosed as leukaemia: a case report and review of the literature.

Background: Necrotizing pneumonia and hyperleukocytosis, to the extent of that seen in leukaemia, is a rarely reported presentation. The commonest trigger of such a presentation is an inflammatory process caused by an overwhelming infection which leads to bone marrow irritation. However, the misdiagnosis of this clinical entity as leukaemia should be avoided at all costs so as to avoid the anxiety associated with a diagnosis of cancer, both to the patients and their families.

Case Presentation: Here, we report the case of a 22-month-old boy who was referred to our Pediatric Oncology Unit (POU). Owing to a high total leukocyte count (TLC) of 98,000 cells/µl, there was a strong suspicion of leukaemia. The boy had been reviewed at another hospital where he presented with fever and cough refractory to the commencement of tuberculosis medications as a result of chest radiography findings. Laboratory investigations performed on admission in the POU were negative for leukaemia and other myeloproliferative disorders. A chest computer tomography (CT) scan was performed to delineate opacification in the right middle lobe. This revealed multiple necrotic and emphysematous foci in line with a diagnosis of necrotizing pneumonia. Subsequently, the patient responded well to a course of piperacillin- tazobactam. The TLC normalized and the cough and fever resolved over a period of 2 weeks.

Conclusion: Here, we describe a particularly rare case of leukaemoid reaction with a massive leukocyte count. Such patients can be easily misdiagnosed as having leukaemia or other myeloproliferative disorders, especially in settings with limited diagnostic availability. Such misdiagnosis can cause undue stress on the patient and their families. Thus, it is important that patients presenting with these symptoms should undergo a thorough review of history, physical examination and a structured workup.