positron emission tomography ( pet ) is a noninvasive medical imaging modality that produces functional rather than anatomical images , thereby providing greater insight to the patient 's condition . assessment of metabolism by pet provides the sensitive detection of tissue viability based on the integrity of cardiac substrate metabolism . a 48-year - old male , a known case of friedreich 's ataxia ( frda ) complained of swelling of lower extremities and low ejection fraction on echocardiography ( echo ) . his two - dimensional - echo showed an ejection fraction of 15% , dilated left atria and ventricle . initially , patient was injected with 10 mci tetrofosmin . after waiting for 45 min rest tetrofosmin images patient was 6 h fasting with a baseline sugar : 128 mg / dl . fifty milligram oral glucose load was given , and 1 h later blood sugar was 198 mg / dl . two units iv insulin ( actrapid ) was administered ; however , the blood sugar after  h was 230 mg / dl . on rechecking blood sugar again after  h increased to 249 mg / dl . one hour later , sugar level reduced to 123 mg / dl after which fluorodeoxyglucose ( fdg ) was injected . tetrofosmin images [ figure 1 ] showed an enlarged left ventricular cavity with moderate perfusion defect in the apex , apical anterior , apical inferior wall of myocardium . gated images showed global hypokinesia with akinetic mid and basal inferior wall , ejection fraction of 39% . fdg images [ figure 2 ] were acquired 1 h , 2 h , and 3 h later . tetrofosmin images showed perfusion defect images acquired at the interval of 1 h , 2 h , and 3 h post fluorodeoxyglucose administration show a similar picture of poor fdg uptake friedreich 's ataxia is an inherited ( genetic ) , progressive disorder of the nervous system that affects balance , coordination , movement , and sensation . the first symptoms of frda usually occur before age 20 , but occasionally , onset can be as late as the 50s . the disorder is  recessive  ( when both parents are frda carriers , they have a one - in - four chance in each pregnancy of conceiving a child who will develop the disease ) . males and females are equally affected frda , due to defects in a gene on chromosome 9 that carries the  recipe  , or  code  , for a cellular protein known as frataxin . the defects keep the affected cells from making a normal amount of frataxin . without frataxin , iron builds up in the mitochondria and damages them . the resulting cellular  energy shortage the cells most affected are those that transmit sensory and movement signals through long fibers . preliminary studies of insulin binding to erythrocytes suggest a difference in the binding characteristics among diabetic frda patients , while the binding in the nondiabetic frda group is similar to that of nondiabetic controls . in most viability studies , the normal myocardium under glucose load and insulin stimulation shows good fdg uptake . under normal conditions , however , areas of ischemia switch preferentially to glucose metabolism and have increased fdg uptake relative to perfusion . thus , high serum glucose and insulin levels and low free fatty acid level promote fdg uptake . the rest of the normal myocardium also did not surprisingly show any fdg uptake despite of repeated delayed images up to 3 h postfdg administration as insulin resistance is associated with a reduction in the affinity of insulin receptors and membrane abnormality that alters the binding function of the insulin receptor . although there is no known cure for frda , many of the problems imposed by the disease can be treated . orthopedic intervention , which may include surgery , can alleviate scoliosis , and orthopedic appliances and physical therapy can help prolong ambulation . even nondiabetic patients suffering from other diseases with insulin resistance due reduction in affinity of insulin receptors or membrane abnormality could surprise us as in our case .
a 48-year - old man , a known case of friedreich 's ataxia ( frda ) underwent cardiac fluorodeoxyglucose ( fdg ) positron emission tomography -computed tomography ( pet / ct ) for evaluation of myocardial viability . 
 tetrofosmin images showed an enlarged left ventricular cavity with small mid and basal inferior and apical infarct global hypokinesia with ejection fraction of 39% . 
 fluorodeoxyglucose images showed poor quality myocardial images . 
 friedreich 's ataxia is associated with a high incidence of diabetes mellitus . 
 non - diabetic patients with friedreich 's ataxia have insulin resistance . 
 this is associated with a reduction in the affinity of insulin receptors and membrane abnormality that alters the binding function of the insulin receptor .