dermatomyositis ( dm ) , as an idiopathic inflammatory myopathy , is associated with increased risk of malignant disease . non - hodgkin s lymphoma and ovarian , lung , gastric , colorectal , and pancreatic cancers are all commonly associated with dm . cholangiocarcinoma with paraneo - plastic dm is extremely rare [ 3 - 5 ] , and the whole body positron emission tomography - computed tomography(pet - ct ) finding of paraneoplastic dm is rarely reported . in this report , we describe a rare case of paraneoplastic dm in a patient with cholangiocarcinoma , showing strong diffuse proximal muscle uptake in a whole body pet - ct scan before any muscle symptoms developed . a 66-year - old woman with a history of hypertension experienced general weakness , anorexia , and poor oral intake over a 2-month period . laboratory tests showed elevated levels of aspartate aminotransferase and alanine aminotransferase , which were 419 iu / ml and 176 iu / ml , respectively . tests for antibodies against hepatitis b surface antigen , hepatitis c virus , and human immunodeficiency were negative . the patient had serum carbohydrate antigen 19 - 9 levels of 9,446 u / ml ( reference range , 0 to 37 u / ml ) , alpha - fetoprotein levels of 27.52 ng / ml ( reference range , 0.89 to 8.78 ng / ml ) , and carcinoembryonic antigen levels of 2.4 ng / ml ( reference range , 0 to 5 ng / ml ) . a computed tomography ( ct ) scan of the abdomen and pelvis revealed multiple masses in lobes of the liver , peritoneal nodules , and multiple enlarged lymph nodes in the retrocrural , aortocaval , paraaortic , and external iliac areas . magnetic resonance imaging ( mri ) of the patient s liver indicated multiple , gradually enhancing peripheral masses in both lobes of the liver ; the largest of these masses measured 7.5 cm . a biopsy of the liver mass indicated cholangiocarcinoma ( fig . 1a ) . consistent with a diagnosis of cholangiocarcinoma , immunostaining for cytokeratin 19 was positive ( fig . 1b ) and staining for alphafetoprotein was negative ( not shown ) . while awaiting chemotherapy , the patient developed muscle weakness in her lower extremities , which progressed rapidly ; she was unable to ambulate 10 days later . , it was found that the flexion power of both hips was decreased to grade iii , and knee flexion was reduced to grade iv . in the distal muscle groups , muscle strength was intact . the patient had bluish - purple skin lesions on her upper eyelids , and erythematous papules over her knuckles ( gottron s sign ) . interestingly , a whole body pet - ct scan ( briograph mct 40 , siemens medical solutions , knoxville , tn ) , which was performed a week before the onset of muscle weakness , indicated diffuse [ f]-fluorodeoxyglucose ( fdg ) uptake in the skin and whole muscles , in addition to both of the hepatic lobes , lymph nodes , lung , peritoneum , and l3 vertebra ( figs . symmetrically proximal and bilateral fdg uptake was primarily in the shoulders , upper arms , back , hips , and thigh muscles . the patient had elevated creatine phosphokinase ( ck ) levels of 7,748 iu / l ( reference range , 20 to 270 iu / l ) , lactic dehydrogenase levels of 1,833 iu / l ( reference range , 100 to 225 iu / l ) , and aldolase levels of 32.6 u / l ( reference range , below 7.6 electromyography revealed moderate myopathy . a muscle biopsy taken from the patient s upper right thigh showed degenerating and regenerating myofibers with variable sizes , endomysial fibrosis , and fat ingrowth , but no evidence of vasculitis or tumor cell infiltrates ( fig . the patient was diagnosed with cholangiocarcinoma with paraneoplastic dm , and treatment with high - dose corticosteroids and chemotherapy consisting of gemcitabine , and cisplatin was initiated . after two cycles of chemotherapy , ct and whole body pet - ct scans showed a marked reduction in cancer burden . cholangiocarcinoma with paraneoplastic dm is extremely rare [ 3 - 5 ] , and biopsy - proven cholangiocarcinoma in an established dm patient has only been reported by knowles et al . . the whole body pet - ct findings of paraneoplastic dm are also rare , even though pet - ct is frequently used as a tool for detecting and staging of malignant tumors . the principle underlying this use of pet - ct is that cancer cells use more energy than normal tissues , and therefore , take up and retain more glucose than noncancerous cells . in general , skeletal muscles show no significant uptake of the tracer in a well - prepared patient ; however , high muscle uptake of fdg , due to highly metabolically active cells , may be observed in association with inflammatory conditions , such as musculoskeletal infection , vasculitis , and myositis . pathologic fdg uptake can also be seen in primary muscle tumors , metastases to muscles , and other uncommon malignant process , e.g. , muscle lymphoma . interestingly , diffuse fdg uptake in the bilateral proximal muscles of our patient appeared before the onset of muscle weakness , and our initial interpretation of the high muscle uptake was metastasis to the muscles from the underlying cholangiocarcinoma . this case indicates that muscle inflammation can precede the onset of clinical dm symptoms . as such , paraneoplastic dm should be considered as a possible diagnosis in cancer patients with abnormal tracer muscle uptake in pet - ct scans . recent studies have suggested that dm might arise as an autoimmune response against cancer which cross - reacts with regenerating muscle cells . have reported that myositis - specific autoantigens are expressed in both tumor cells and undifferentiated myoblasts , which indicate that these cells express similar proteins , and that these proteins can serve as autoantigens . have previously identified a novel autoantibody ( anti-155/140 antibody ) , which is highly specific for paraneoplastic dm . in this context , the successful treatment of underlying malignant disease might improve the clinical course of myositis because it decreases tumor proteins , which serve as autoantigens ; indeed , improvement of dm was observed after cancer treatment . however , our patient did not show any significant improvement in muscle strength following the treatment of underlying malignancy . one possible explanation for this is that a high tumor burden decreases relatively slowly with cytotoxic chemotherapy . another explanation could be that the patient s rapid myositis progression and refractoriness to therapy was indicative of autoimmune antibodies that are reactive against the signal recognition particle ( srp ) . anti - srp antibodies are detected in ~5% of patients with idiopathic inflammatory myopathy , and the presence of anti - srp antibodies is frequently associated with acute onset severe myopathy . acute onset severe myopathy is associated with muscle enzyme elevation and systemic features , including dysphagia , and has been shown to be refractory to standard treatments . b cell depletion , using rituximab , has been used in patients with refractory dm , and good results have also been reported in the treatment of anti - srp myopathy . in such cases , perivascular muscle fiber necrosis and endomysial fibrosis , with little or no inflammatory cell infiltrates , are frequently found . in the present case , anti - srp myopathy was considered as a potential diagnosis , given the rapid progression of muscle weakness , relatively high levels of ck , endomysial fibrosis with little inflammatory cell infiltration , and refractoriness to treatment . however , the laboratory test for anti - srp was not available ; hence , the investigation did not proceed further . paraneoplastic dm , although rare , can occur with a cholangiocarcinoma , and inflammatory infiltrates observed using pet scans can precede the onset of clinical muscle sympoms . once identified , this case illustrates the importance of considering paraneoplastic dm as a possible differential diagnosis in the assessment of cancer patients who present with abnormal tracer muscle uptake in pet - ct scans . in such cases ,
cholangiocarcinoma with paraneoplastic dermatomyositis ( dm ) is extremely rare , and the whole body positron emission tomography - computed tomography ( pet - ct ) finding of paraneoplastic dm is rarely reported . 
 we report a 66-year - old woman with metastatic cholangiocarcinoma , initially presented with bilateral proximal muscle uptake on pet - ct without clinical muscle symptoms . 
 the initial interpretation of the high muscle uptake was metastasis to the muscles . 
 however , while awaiting for chemotherapy , muscle weakness evolved and rapidly progressed . 
 the level of creatine phosphokinase was significantly elevated . 
 electromyography revealed moderate myopathy , and a muscle biopsy showed degenerating myofibers with variable sizes . 
 the diagnosis of paraneoplastic dermatomyositis was made . 
 this case highlights that , although rare , paraneoplastic dermatomyositis can be present with cholangiocarcinoma . 
 also , muscle inflammation can precede the clinical muscle symptoms , and paraneoplastic dm should be considered as a possible differential diagnosis in the assessment of cancer patients who present with abnormal muscle tracer uptake in pet - ct scans .