A renal biopsy was performed on this 78 year old male with history of diabetes mellitus, hypertension and monoclonal gammopathy of undetermined significance (IgG kappa). The serum creatinine at presentation was 3.2 mg/dl and UPCR was 1.8 g/g. The glomeruli diffusely show nodular mesangial expansion with segmental sclerosis and negative Congo red staining, consistent with diabetic glomerulosclerosis. On the other hand, the arteries and arterioles diffusely show deposition of a PAS pale, weakly argyrophilic, Congo red positive amorphous material which shows apple green birefringence upon polarization, consistent with amyloid deposits (Fig 1 and 2, Congo red). Similar deposits are not identified within the glomeruli or tubulointerstitium. Immunofluorescence shows strongly positive vascular “smudgy” staining for kappa light chain, along with diffusely negative staining for heavy chains and lambda light chain. These findings are characteristic of AL amyloidosis (kappa-type) with exclusive vascular involvement. Patients with underlying plasma cell dyscrasias or lymphoproliferative disorders may develop different forms of renal disease related to deposition of monoclonal immunoglobulins, an example of which is AL amyloidosis. AL amyloidosis may affect any, and frequently all compartments of the renal parenchyma, including glomeruli, vessels and tubulointerstitium. Such as in this case, a small subset of patients may display amyloid deposits restricted to the vascular structures. These patients have been shown to present with worse renal function and lower levels of proteinuria when compared to patients with diffuse involvement (see reference). Furthermore, kappa light chain-type amyloidosis is proportionally more frequent then lambda-type in patients with vascular-limited disease than in those patients with diffuse involvement.
Eirin A, Irazabal MV, Gertz MA, et al. Clinical features of patients with immunoglobulin light chain amyloidosis (AL) with vascular-limited deposition in the kidney. Nephrol Dial Transplant. 2012; 27: 1097-1101.
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