AL amyloidosis with non-amyloid forming monoclonal immunoglobulin deposition; a case mimicking AHL amyloidosis.

Abstract

BACKGROUND:

Immunoglobulin heavy-and-light-chain amyloidosis (AHL amyloidosis) is a newly established disease entity where both the immunoglobulin heavy-chain and light-chain compose amyloid fibrils. The immunoglobulins responsible for the amyloid fibrils are generally identified by immunostaining and/or laser microdissection-liquid chromatography-tandem mass spectrometry (LMD-LC-MS/MS). However, both techniques do not biochemically differentiate immunoglobulins that formed amyloid fibrils from non-responsible immunoglobulins.

CASE PRESENTATION:

We herein report a case of 67-year-old female patient with renal amyloidosis due to lymphoplasmacytic lymphoma secreting monoclonal immunoglobulin M (IgM)-kappa. Renal immunostaining monotypically positive for IgM-kappa and LMD-LC-MS/MS identification of mu heavy-chain and kappa light-chain were consistent with the diagnosis of AHL amyloidosis. In order to confirm that both the immunoglobulin heavy-chain and light-chain were forming amyloid fibrils, we performed LC-MS/MS of renal amyloid fibrils isolated by the traditional amyloid purification method. The additional LC-MS/MS identified kappa light-chain only without any heavy-chain component. These results were suggestive that amyloid fibrils were composed by kappa light-chain only and that the mu heavy-chain identified by immunostaining and LMD-LC-MS/MS was derived from the non-specific co-deposition of monoclonal IgM-kappa.

CONCLUSION:

The case was AL amyloidosis with non-amyloid forming monoclonal immunoglobulin deposition. While immunostaining and LMD-LC-MS/MS are irreplaceable techniques to classify amyloidosis, confident exclusion of the present condition should be required to diagnose AHL amyloidosis.

• Authors: Shun Manabe, Chihiro Iwasaki, Michiyasu Hatano, Fuyuki Kametani, Masahide Yazaki, Kosaku Nitta, Michio Nagata
• Journal: BMC nephrology (BMC Nephrol) Vol. 19 Issue 1 Pg. 337 (11 22 2018) ISSN: 1471-2369 [Electronic] England
• PMID: 30466387 (Publication Type: Case Reports, Journal Article)

Chemical References

• Immunoglobulin Heavy Chains
• Immunoglobulin Light Chains

Topics

• Aged
• Diagnosis, Differential
• Female
• Humans
• Immunoglobulin Heavy Chains (blood)
• Immunoglobulin Light Chains (blood)
• Immunoglobulin Light-chain Amyloidosis (blood, diagnosis)