the causes are multifactorial , with extramedullary pulmonary hematopoiesis being described as a rare etiological factor ( 2 ) . this occurs in conditions such as myeloproliferative disorders , hemoglobinopathies and marrow infiltrating diseases . in chronic myeloproliferative disorders , extramedullary hematopoiesis in the lungs may be suspected on computed tomography ( ct ) chest scans in the presence of diffuse ground - glass opacities or interstitial thickening ( 3 ) . we report the case of a 66-year - old man in whom chest ct scan did not reveal any lung parenchymal abnormality . a pulmonary extramedullary hematopoiesis causing pulmonary hypertension and severe tricuspid regurgitation was diagnosed on technetium-99 m ( tc-99 m ) sulfur colloid bone marrow scan and single - photon emission computed tomography ( spect)/ct . a 66-year - old man with a known primary myelofibrosis ( diagnosed in december 2008 at an outside institution ) presented to our hospital with complaints of shortness of breath and abdominal bloating in march 2012 . he had multiple hospital admissions for the worsening of its dyspnea over the previous two years . on clinical examination , he was dyspneic with an elevated jugular venous pressure and bipedal pitting edema . the total white cell count was markedly raised ( 41.2  10/l ) with a low hemoglobin level ( 5.3 g / dl ) . a ct pulmonary angiogram did not show any pulmonary embolism ; however , the right atrium and the main pulmonary arteries were dilated , suggesting a pulmonary hypertension with reflux of contrast into the inferior vena cava and hepatic veins ( fig . 1e ) . the two - dimensional echocardiography confirmed a severe tricuspid regurgitation with marked right atrial dilatation and moderately impaired right - ventricular systolic function . a tc-99 m sulfur colloid bone marrow scan with spect / ct imaging was performed ( symbia , siemens medical solutions , erlangen , germany ) with a background history of primary myelofibrosis to exclude pulmonary hematopoiesis as the cause of pulmonary hypertension . the planar gamma imaging showed a hepatosplenomegaly with increased tracer accumulation in the spleen , compatible with an increased hematopoietic activity resulting from an underlying myelofibrosis ( fig . a moderate degree of tracer activity in a diffuse pattern was noted in both thoracic regions ( fig . the spect / ct imaging confirmed the location of an increased thoracic tracer activity in the lungs ( fig . a lung biopsy was not carried out in view of the increased risk of pulmonary hemorrhage in the presence of pulmonary hypertension . a hydroxyurea treatment was started for the patient to control the markedly raised total leukocyte count and massive splenomegaly . concurrently , he was referred to a short course radiation - therapy to the lungs with view to achieve control of the pulmonary hematopoiesis . the usual sites of extramedullary hematopoiesis are the liver , spleen and intrathoracic paraspinal regions ( 3 ) . lungs and pleura are rare sites of extramedullary hematopoiesis with less than forty cases of pulmonary extramedullary hematopoiesis described in the current literature ( 4 ) . a causal association between pulmonary hematopoiesis leading to dyspnea and pulmonary hypertension has been postulated in few case reports and a limited number of cohort studies ( 1 , 2 , 5 ) . ( 1 ) listed hematopoietic infiltration of the pulmonary parenchyma as one of the probable causes of pulmonary hypertension in patients with myelofibrosis . ( 6 ) described the case of a 49-year - old man in whom dyspnea due to pulmonary hematopoiesis was a presenting feature of myelofibrosis . in most of case reports describing pulmonary extramedullary hematopoiesis , the diagnosis was suspected on the chest ct scan due to abnormalities such as ground - glass opacities ( 4 ) or interstitial septal thickening ( 6 ) . ground - glass opacities per se are non - specific ct findings with more common differentials of congestive cardiac failure and lung infection in patients presenting with dyspnea . in the setting of myelofibrosis , additional possibilities include pulmonary extramedullary hematopoiesis , thromboembolism or chemotherapy - induced lung toxicity ( 7 ) . in our case , an increased lung uptake of tc-99 m sulfur colloid is not specific to an extramedullary pulmonary hematopoiesis . it can occur after liver and bone marrow transplantation , hepatic veno - occlusive disease , liver cirrhosis , liver metastases or hepatic chemotherapy toxicity ( 8) . a possible mechanism is the stimulation of reticulo - endothelial elements in the lung interstitium or an induction of pulmonary macrophages . the localization of increased tracer activity in the lungs was sufficiently demonstrated on spect / ct imaging . in addition , spect / ct imaging also aided in confirming absence of tracer activity within the pleural spaces , thus excluding any pleural site of extramedullary hematopoiesis . we believe that spect / ct imaging , if available , should be included in the imaging protocol of suspected pulmonary hematopoiesis , as it can localize tracer activity in the lungs or pleura , which is not possible on a two - dimensional planar imaging . a histopathological confirmation of pulmonary hematopoiesis could not be obtained as a lung biopsy was not performed in our patient . however , pulmonary hematopoiesis was considered the most likely diagnosis in the absence of other complicating factors which could have resulted in an increased lung uptake of tc-99 m sulfur colloid . in summary , extramedullary pulmonary hematopoiesis in myelofibrosis leading to pulmonary hypertension and tricuspid regurgitation is a rare condition . this case report highlights the utility of tc-99 m sulfur colloid bone marrow scan in cases of unexplained pulmonary hypertension with underlying myeloproliferative disorders . we believe that an inclusion of spect / ct imaging helps to confirm and characterize the pulmonary involvement .
extramedullary pulmonary hematopoiesis is a rare entity with a limited number of case reports in the available literature only . 
 we report the case of a 66-year - old man with known primary myelofibrosis , in whom a technetium-99 m sulfur colloid bone marrow scan with single - photon emission computed tomography ( spect)/ct revealed a pulmonary hematopoiesis as the cause of pulmonary hypertension and severe tricuspid regurgitation . to the best of our knowledge , this is the first description of technetium-99 m sulfur colloid spect / ct imaging in this rare condition .