99mTc-DPD scintigraphy in transthyretin-related familial amyloidotic polyneuropathy

Familial amyloidotic polyneuropathy (FAP) caused by amyloidogenic transthyretin (ATTR) mutations is the most common form of hereditary amyloidosis. We investigated the diagnostic value of the bone scanning agent technetium-99m 3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD) in this disease. Eight patients (four males, four females; age 54.4+/-8.3 years, range 43-67 years) with ATTR-FAP proven by immunohistochemistry and molecular analysis and a control group comprising ten oncological out-patients (five males, five females; age 53.4+/-8.5 years, range 34-66 years) without evidence of bony metastases were studied using 99mTc-DPD. Whole body tracer retention was 80.1%+/-10.3% (range 65.1%-94.8%) in FAP patients and 55.7%+/-8.1% (range 40.2%-66.7%) in controls at 3 h p.i. (P<0.001), and cardiac uptake was 7.3%+/-2.2% (range 4.2%-10.1%) in FAP patients and 3.1%+/-0.5% (range 2.3%-4.0%) in controls (P<0.001). The heart/whole body uptake ratio was 8.9%+/-1.7% (range 6.5%-11.0%) in FAP patients and 5.6%+/-0.5% (range 5.1%-6.8%) in controls (P<0.001). The three FAP patients with the highest cardiac tracer uptake had cardiomyopathy or arrhythmia. 99mTc-DPD scintigraphy is proposed as a simple and valuable diagnostic aid to evaluate the severity of the disease and the risk of concomitant heart problems.