What is the pentagonal (P) component of amyloid?

Updated: May 09, 2019
  • Author: Robert O Holmes, Jr, DO; Chief Editor: Herbert S Diamond, MD  more...
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Pentagonal (P) component comprises approximately 5% of the total protein in amyloid deposits. This component is derived from the circulating serum amyloid P (SAP) component, which behaves as an acute-phase reactant. The P component is one of the pentraxin group of proteins, with homology to C-reactive protein. In experimental animals, amyloid deposition is slowed without the P component.

Radiolabeled material homes to amyloid deposits; therefore, this component can be used in amyloid scans to localize and quantify amyloidosis and to monitor therapy response. Radiolabeled P component scanning has proven clinically useful in England, where the technology was developed, but it is available in only a few centers worldwide.

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