a reactive leucocytosis , with a significant increase in early neutrophil precursors , exceeding 50,000/mm is referred as leukaemoid reaction . these reactions are generally benign , but may imitate more serious conditions such as chronic myelogenous leukaemia . leukemoid reaction may be a paraneoplastic manifestation of several cancers such as lung , gastrointestinal , genitourinary , ovarian , head and neck cancers and hepatocellular carcinoma . non - cancerous conditions that can precipitate a leukemoid like state include those of situations of stress , infection and inflammation . the cytokines implicated in this process include granulocyte - macrophage colony - stimulating factor ( csf ) , granulocyte - csf ( g - csf ) , interleukin-3 ( il-3 ) and il-6 . a 54-year - old female with angina ( nyha - class ii ) , double vessel disease ( left main coronary artery equivalent , distal left anterior descending artery - 95% , distal circumflex artery - 80% ) with good left ventricular ( lv ) function was referred for coronary revascularisation . pre - operative investigations revealed a white blood cell ( wbc ) count of 12,900/cmm ( neutrophils 61% , monocytes 6% lymphocytes 29% eosinophils 4% ) and urinalysis was within the normal limits . the raised total leukocyte count ( tlc ) was possibly attributed to her type 2 diabetic status , the radial artery angiogram procedure that was done 2 days prior to the pre - anaesthetic check - up and possibly to the recent angina that the patient had at the time of admission ( 1 week ) . although she remained asymptomatic an early coronary artery bypass grafting ( cabg ) was planned . cabg was performed using the left internal mammary artery and left great saphenous vein graft . cardiopulmonary bypass ( cpb ) time was 110 min with aortic cross - clamp for 58 min , using antegrade cold crystalloid cardioplegia . post - operatively ( on the day of surgery ) routine blood tests demonstrated a mild leucocytosis ( 20,900/cmm ) with marked neutrophilia ( 71% ) , lymphocytosis ( 20% ) , and monocytosis ( 9% ) . on the first post - operative day the tlc increased to 25,000/cmm and to 29,500/cmm on second post operative day . this increasing trend in the wbc prompted us to change the antibiotic from first line antibiotics ( cefuroxime + ofloxacin ) to second line antibiotics ( cefoperazone + sulfactum + ofloxacin ) assuming a subclinical infection due to her diabetic status . blood , urine and sputum culture showed no growth of organisms after 48 h. laboratory work - up for infective ( bacterial and parasitic ) aetiology revealed negative results . the usual cardiac supports were tapered off on the third post - operative day and the patient shifted to intermediate care unit on the fifth day in spite of her rising total wbc count . the wbc count reached 33,000/cmm on the third day and 41,000/cmm on the 4 post - operative day without any signs of infection . on the fifth post - operative day the tlc increased to 49,400/cmm ( neutrophils 54% , lymphocytes 30% , and monocytes 16% ) . inflammatory parameters were mildly elevated ( c - reactive protein [ crp ] 38 mg / l ) . a peripheral smear showed marked leucocytosis , predominately neutrophils and mild shift to left was noted with presence of myelocytes and band forms . red blood cell ( rbc ) were chiefly normocytic , with increased polychromasia and occasionally normoblast . serum procalcitonin to rule out sepsis was not assessed as the patient was clinically stable with mildly elevated crp levels and also keeping in mind the limited resources , the cost factor and delay in reporting . chest x - ray and ultrasound abdomen did not reveal obvious causes of possible solid viscera tumours that can cause a leukemoid reaction . computed tomography ( ct ) of chest , abdomen and pelvis were postponed , to be obtained at review . on 10 post - operative day thus a provisional diagnosis of leukemoid like reaction - post cabg surgery was made and patient discharged on the 10 post - operative day with an advice for follow - up 1 week later . the tlc was 15,000/cmm with neutrophils 68% , eosinophil 2% , monocytes 6% , and lymphocytes 24% on her next visit which confirmed the diagnosis of leukaemoid like reaction . leukocytosis exceeding 50,000 wbc / cmm with a significant increase in early neutrophil precursors is referred to as a leukaemoid reaction . in most cases certain types of chronic infection such as mononucleosis , malaria , and tuberculosis , certain types of cancers , hodgkin 's disease and autoimmune anaemia may cause leukemoid reactions [ table 1 ] . thus it is a clinical syndrome in which changes are found in the peripheral blood similar to what occurs in people with leukaemia , but not the result of leukaemic disease . leukaemoid reaction has also been reported to occur in allergic reaction of phenobarbital , an aromatic anticonvulsant drug [ table 1 ] . common causes of leukaemoid reaction in our patient , the possible cause of the raised tlc with monocytosis during the pre - operative time would have been due to the angina pectoris , which she had at the time of admission . the study by maekawa et al . showed that the peak monocyte count had a significant positive correlation with lv end - diastolic volume obtained from pre - discharge left ventriculography . patients with pump failure or lv aneurysm had higher peak monocyte counts than those without these complications . multivariate analyses showed that a peak monocyte count 900/cmm was an independent determinant of pump failure , lv aneurysm and long - term adverse cardiac events . post cabg our patient presented with a rise in tlc which was due to increased neutrophil count along with relative lymphocytosis and monocytosis . the possible causes resulting in the scenario could be malignancies ( carcinoma , plasma cell myeloma , or lymphoma ) , chronic infections or autoimmune disorders . all laboratory work - up for acute and chronic infective ( bacterial and parasitic ) aetiology revealed negative results . blood peripheral smear showed marked leucocytosis , with predominately neutrophils with presence of myelocytes and band forms . the other possible reason for this abnormal behaviour may be due to inflammatory response to the extra - corporeal circulation . studies have proved that after revascularisation the total blood monocyte counts tend to rise temporarily , peaking between day 2 and 3 after intervention . the resident macrophages in the myocardium are activated and synthesize and secrete humoral factors that cause monocytopoiesis . cardiac surgery produces an altered activation of the inflammatory response due to the combination of surgical trauma , cpb and ischemia - reperfusion injury . in the case of our patient , it appears that the inflammatory storm generated by cardiac surgery with cpb precipitated a dramatic myelomonocytic leukemoid reaction , with no clinical picture of sirs and multiple organ dysfunction syndromes . the question that arose was why our patient responded to the inflammatory stress of surgery in such an unpredictable fashion . our prime suspect was that of undiagnosed underlying chronic myelomonocytic leukaemia ( cmml ) or any other malignancies , which may progress to the acute phase of leukemoid reaction , a complex and poorly understood response by the bone marrow to stress . in this patient , it appears that the inflammatory storm generated by cardiac surgery with cpb precipitated a dramatic myelomonocytic leukemoid like reaction . a leukemoid reaction may rarely prove rapidly fatal although the cause of disease acceleration and potential remitting factors remain obscure . our patient was planned for a later bone marrow biopsy to exclude leukaemia and finally demonstrated a lack of myeloid clonality . thus with the provisional diagnosis of leukaemoid reaction , investigations such as bone marrow biopsy , lap score and ct thorax abdomen pelvis were deferred in consultation with the physicians and surgeons . investigation of the bone marrow including immunophenotyping could have helped us to differentiate between leukaemia and a leukaemoid reaction . lap scoring could confirm our provisional diagnosis , while ct thoracoabdominopelvis can help to rule out solid tumours that commonly produce leukaemoid reaction . a paraneoplastic leukaemoid reaction can be caused by increased serum levels of g - csf or other growth factors , which are considered to be produced by the malignant cells , mostly from an endothelial tumour . the only report of off - pump cab in a patient with cmml , performed via a median sternotomy , highlighted concerns over leukaemoid transformation and the assumed benefits of a reduction in cytokine release . when wbc counts increase grossly , a cause outside the bone marrow has to be searched for . the leucocyte count was showing increasing trend throughout the post operative period after cabg in the present case and no clear source could be found , including sepsis and hence , we termed it as leukaemoid ( wbc count > 50,000/cmm ) like reaction .