imatinib mesylate is a small molecule inhibitor of multiple tyrosine kinases and selectively prevents phosphorylation of bcr - abl and inhibits downstream signaling and growth of bcr - abl  positive cells . it was first approved for the treatment of chronic myeloid leukemia ( cml ) in 2001 and for the treatment of gastrointestinal stromal tumor ( gist ) in 2003 . this revolutionized the treatment of cml with more than 90% patients remaining stable in the past 5 years . imatinib is associated with various adverse effects which include cardiovascular side effects such as edema , anasarca , pericardial , or pleural effusion and rarely cardiac failure . although pleural effusions have been reported with imatinib , it is a rare side effect . we present a case of imatinib - associated pleural effusion for its rarity and its potential to be overlooked by physicians . an 88-year - old man presented with a 2-week history of gradually progressive breathlessness and dry cough . his history was remarkable for hypertension and coronary artery bypass grafting done 8 years ago . he was diagnosed with gist 4 months ago when he presented with gastric discomfort and a computed tomography ( ct ) scan of the abdomen showed a 12 cm  11 cm  8.5 cm posterior mediastinal mass . a subsequent endoscopic ultrasound - guided biopsy showed tumor cells positive for c - kit and dog-1 . he was commenced on tablet imatinib 400 mg / day for his gist , but after 1 month of the treatment , he began to complain of breathlessness on exertion . there was no history of tuberculosis or tuberculosis contact . on examination , he was mildly tachycardic with a pulse rate of 90/min . he had no pallor , icterus , cyanosis , clubbing , lymphadenopathy , or pedal edema . his respiratory system examination revealed diminished breath sounds in the right infrascapular and infraaxillary area . his complete blood count , renal function tests , and liver function tests were all normal . his transthoracic two - dimensional echocardiogram showed normal left ventricular ( lv ) ejection fraction of 55% . a chest radiograph [ figure 1 ] showed a right pleural effusion and high - resolution ct chest [ figure 2 ] showed a large right - sided pleural effusion and unchanged posterior mediastinal mass with no consolidation or lymphadenopathy . chest x - ray showing a right - sided pleural effusion high - resolution computed tomography chest showing right - sided pleural effusion with no parenchymal abnormality he underwent a thoracentesis of the pleural fluid ; 1100 ml was aspirated . results of pleural fluid aspiration were : protein : 3.3 g / dl ( total serum protein : 5.4 g / dl ) ; lactate dehydrogenase ( ldh ) : 223 iu / l ( serum ldh : 280 iu / l ) ; white blood cell count : 1040/mm ( 50% lymphocytic ) ; adenosine deaminase ( ada ) : 4.1 ( normal : 040 pleural fluid aerobic and tuberculosis cultures and genexpert were all negative . he was diagnosed to have an exudative effusion with a low ada . an oncologist 's opinion was sought who ruled out metastasis as a cause of the effusion . in the absence of other causes of pleural effusion , a diagnosis of imatinib - induced pleural effusion imatinib was withdrawn ; the patient gradually improved and a repeat chest x - ray at 3 months poststoppage of drug showed complete resolution and no refilling of the fluid [ figure 3 ] . the patient declined any further treatment for his gist and was not put on any other medication . he remains under regular chest radiograph and sonography follow - up over 1 year and has no recurrence of his effusion . drug - related pleural disease is rare although many commonly used drugs are known to affect the pleura . imatinib - induced fluid retention is a common adverse effect and one of the important dose - limiting toxicities . specifically , fluid retention manifests as edema in periorbital regions , lower extremities , and/or body in approximately 80% patients which is usually mild and manageable . severe fluid retention resulting in generalized edema ( anasarca ) , ascites , pleural , or pericardial effusions is rare and seen in around 2% of gist patients and hence poorly studied . two distinct types or courses of pleural effusion are seen : ( 1 ) acute / progressive fluid formation that occurs early after drug initiation or dose escalation and ( 2 ) intermittent / steady fluid formation with mild , occasional , or persistent fluid formation . imatinib - induced pleural effusion appears to be dose dependent , with higher incidence in patients treated with 400 mg twice a day . the suggested mechanism is probably related to kinase inhibition : imatinib potently inhibits platelet - derived growth factor receptor - b which is expressed in pericytes and is involved in the regulation of angiogenesis . imatinib can also induce cardiotoxicity which can range from asymptomatic lv dysfunction to congestive heart failure . hence , it should be ruled out in any patient who presents with breathlessness on imatinib therapy . while pleural effusion due to imatinib therapy is rare , it is commonly seen in patients treated with dasatinib which is a potent oral second - line bcr / abl tyrosine kinase inhibitor . in a review of 915 chronic phase , cml patients previously treated with imatinib or dasatinib or both , 30% of patients treated with dasatinib had a history of pleural or pericardial effusions , whereas only 2% of patients treated with imatinib developed effusions . treatment of tyrosine kinases induced pleural effusion includes therapy interruption , drug dose reduction , steroids , and diuretics and only in a few severe instances , therapeutic thoracentesis . with adequate management and monitoring of patients with predisposing factors , the majority of them can continue therapy with the drug , even if this complication occurs . thus , in conclusion , any new pleural effusion should not be mistakenly interpreted as a sign of metastases or worsening tumor , especially when the primary malignancy is stable . for best patient care in the era of molecular - targeted therapeutic agents , a multidisciplinary approach with close collaboration between oncologists and radiologists is essential to assess treatment response as well as toxicity of tyrosine kinase inhibitors .
imatinib is a tyrosine kinase inhibitor and has rarely been reported to cause pleural effusion . 
 we report the case of an 88-year - old male , known case of gastrointestinal stromal tumor on treatment with imatinib , who presented with a 2-week history of cough and dyspnea . 
 he was diagnosed to have a right - sided pleural effusion and thoracentesis of the fluid revealed an exudate with low adenosine deaminase and negative cytology . 
 withdrawal of the drug lead to resolution of symptoms . 
 we report this case to highlight the side effect profile of imatinib and warn physicians regarding this potential adverse effect which may be mistaken for metastasis or infection .