[440] Mass Spectrometry Based Proteomic Analysis Identifies Two Distinct Types of Cutaneous Amyloidosis

JC Berg, JA Vrana, JD Theis, JD Gamez, TF Flotte, RH Weenig, AH Dogan. Mayo Clinic, Rochester, MN

Background: Amyloid present in the skin can represent involvement by either a systemic disease or a primary, localized process. While the nonspecific amorphous deposits appear the same by light microscopy, the underlying etiology varies. As the management of amyloidosis targets underlying pathogenesis and may include high risk strategies, accurate classification is a clinical priority. To understand the pathogenesis of cutaneous amyloidosis we utilized a novel microdissection and mass spectrometry based approach to identify two distinct cutaneous amyloid types with characteristic clinico-pathological features.
Design: 15 cases of cutaneous amyloidosis were identified from Mayo Clinic files with corresponding clinical information. In each case, the diagnosis of amyloidosis was confirmed by Congo red reactivity with appropriate color change under polarized light. Amyloid deposits were microdissected, processed and trypsin digested into peptides. The peptides were analyzed by nano-flow liquid chromatography electrospray tandem mass spectrometry (LC-MS/MS). To identify the protein constituents of amyloid deposits, the resulting LC-MS/MS data were correlated to theoretical fragmentation patterns of tryptic peptide sequences from the Swissprot database using Scaffold program. To validate the findings of LC-MS/MS, immunohistochemistry for CK5, CK14, immunoglobulin kappa (IGK) and lambda light chains (IGL), TTR, SAA was performed.
Results: LC MS/MS identified two distinct protein profiles in cutaneous amyloid deposits. In 10 cases the amyloid deposits were enriched in cytokeratin 5 and 14 and, in the remaining 5 cases, peptides representing IGK (4/5) or IGL (1/5) were dominant. SAP was a constituent of both subsets. Interestingly, the cases associated with CK 5 and CK14 amyloid deposition were characterized by pruritis with focal amyloid deposition at the dermal-epidermal junction. None of the patients had clinical evidence of systemic amyloidosis. In contrast, the cases with IGK or IGL deposition lacked a primary skin pathology, but 3 out of 5 had evidence for an underlying systemic plasma cell proliferative disorder.
Conclusions: LC-MS/MS based proteomic analysis of cutaneous amyloidosis identified two distinct cutaneous amyloid types with characteristic clinico-pathological features. Recognition of these two distinct clinico-pathological types of cutaneous amyloidosis is critical in clinical management of these patients.
Category: Dermatopathology

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 72, Tuesday Afternoon