limbic encephalitis is a rare neurological disorder characterized by amnesia , seizures , and psychiatric disturbances , associated with anti - neuronal antibodies that can target either intracellular or neuronal cell surface antigens as voltage - gated potassium channel ( vgkc ) . limbic encephalitis is the second most common non - prion diagnostic of rapidly progressive dementia . it is usually associated with an underlying neoplasm in the context of a paraneoplastic syndrome ( pns ) . here , we describe the first case of anti - vgkc paraneoplastic limbic encephalitis in a patient presenting with a rapidly progressive dementia , in conjunction with a relapsed acute myeloid leukemia ( aml ) . in december 2009 , a 79-year - old man was diagnosed with an aml with minimal maturation ( aml 1 ) , normal karyotype , activating mutation of the fms - like tyrosine kinase-3 internal tandem duplication ( flt3-itd ) , and no mutation of npm1 , cebp1 , or cebp2 . induction was followed by consolidation treatment : six courses of daunorubicin and cytarabine , the last one performed in july 2010 . in march 2011 , anemia , thrombocytopenia and hyperleukocytosis recurred , leading to the diagnosis of relapsed aml 1 with persistence of flt3-itd . he was treated with 10 mg of amlodipine and 16 iu of insulatard . in june 2011 , he lost orientation to place and time , and his nycthemeral rhythm was disturbed expressing agitation in the night and vigilance disturbances . neurological examination found no motor / sensitive deficiency , the reflexes were not perceived but an extrapyramidal rigidity was noted . g / l ) , normal cell count and no malignant cells , normal lactate , normal glucose , negative 14.3.3 protein , negative screening for herpes simplex virus and hhv6 by polymerase chain reaction , and sterile bacterial , viral or fungal cultures . brain magnetic resonance imaging ( mri ) , 2 months after the onset , despite stopping all treatments and natremia correction , the patient presented with a rapidly progressive dementia with hallucinations , extrapyramidal and pyramidal rigidity affecting the limbs and the axis , without seizures or myoclonus , resulting in death in september 2011 . we received the results of the blood screening of neuronal autoantibodies after the patient 's death and detected the presence of anti - vgkc antibodies at 102 pmol / l ( normal at < 30 this patient presented a pns of the central nervous system according to the diagnostic criteria for pns : a non - classic syndrome with positive neuronal antibodies and cancer that develops within 5 years after the diagnosis of the neurological disorder . syndromes associated with antibodies against vgkc are typical limbic encephalitis and morvan 's syndrome , defined by the association of psychiatric symptoms , hallucinations , peripheral nerve hyperexcitability , hyperhydrosis , and other symptoms of autonomic dysfunction . in classical limbic encephalitis , patients presented with mood and sleep disturbances , seizures , hallucinations , and short - term memory loss that can progress to dementia , as in our case . mri was normal , as is the case in up to 45% of patients with limbic encephalitis with vgkc complex antibodies . most of the antibodies directed towards the vgkc complexes are binding to other proteins which are components of the complexes , mainly to lgi1 and caspr2 , and less frequently , to contactin-2 . as all the components of the vgkc complexes are not known , it seems important to resort to cell - based assays for lgi1 , caspr2 , and contactin-2 and the radioimmunoassay for vgkc complexes antibodies , when limbic encephalitis is suspected . only 30% of patients with antibodies against vgkc have tumors , and the cases reported in the literature are more often associated with thymoma , small cell lung cancer and other rare tumors . we performed a chest x - ray to exclude the possibility that our patient harbored an occult cancer in addition to aml 1 but no suspicious lesion was detected . other etiologic studies included the screening for another cause of rapidly progressive dementia   ( for results , see text mentioned above ) . prion disease was ruled out by a normal mri and eeg 2 months after the onset , and was associated with negative controlled 14.3.3 protein . the iatrogenic hypothesis was no longer followed due to the lack of improvement after stopping all treatments . moreover , pharmacovigilance research showed that no treatment received during the course of this disease was considered to be effective . in this case treatment options include corticosteroids , intravenous immunoglobulin or plasma exchange ; about 80% of patients respond to these treatments . to our knowledge , this is the first case of anti - vgkc paraneoplastic limbic encephalitis associated with aml . previously , there has been only one reported case of pns of the central nervous system with vgkc antibodies ( a charcot - marie - tooth syndrome ) related to leukemia . two other cases were reported with limbic encephalitis in patients with non - hodgkin lymphoma [ 6 , 7 ] . most findings of limbic encephalitis in malignant hemopathies are associated with hodgkin lymphoma and none are reported to be caused by vgkc antibodies [ 8 , 9 , 10 ] . more frequent screening looking for pns , including anti - neuronal and anti - vgkc antibodies , should be performed on patients with malignant hemopathies when faced with atypical syndromes of the central nervous system .
among paraneoplastic syndromes ( pns ) associated with malignant hemopathies , there are few reports of pns of the central nervous system and most of them are associated with lymphomas . 
 limbic encephalitis is a rare neurological syndrome classically diagnosed in the context of pns . 
 we report the case of a 81-year - old man who presented with a relapsed acute myeloid leukemia ( aml ) with minimal maturation . 
 he was admitted for confusion with unfavorable evolution as he presented a rapidly progressive dementia resulting in death . 
 a brain magnetic resonance imaging , performed 2 months after the onset , was considered normal . 
 an electroencephalogram showed non - specific bilateral slow waves . 
 we received the results of the blood screening of neuronal autoanti - bodies after the patient 's death and detected the presence of anti - voltage - gated potassium channel ( vgkc ) antibodies at 102 pmol / l ( normal at < 30 
 pmol / l ) . 
 other etiologic studies , including the screening for another cause of rapidly progressive dementia , were negative . 
 to our knowledge , this is the first case of anti - vgkc paraneoplastic limbic encephalitis related to aml .