Fig. 1.

Representative electron microscopic findings of amorphous materials forming amyloid fibrils. A cross section of a sural nerve biopsy specimen from a patient with early-onset Val30Met ATTR from an endemic area. Uranyl acetate and lead citrate stain. Amorphous electron-dense extracellular materials (asterisks) are abundant, particularly at the vicinity of a collection of collagen fibers (circular structures with a diameter of 50–70 nm). Aggregations of small dotty structures (arrows) are often observed among these amorphous materials, suggesting that nonfibrillar oligomeric intermediates are formed during the process of amyloid fibril formation. Mature amyloid fibrils are indicated by arrowheads. Scale bar 0.2 μm