LSUHSC Renal Pathology Consultative Services - Case Study #  4

Case Study #: 4

Clinical History:

40 year old male who presented with renal insufficiency and mild proteinuria. Blood pressure 150/90 Creatinine 2.9 mg/dl (creatinine was 1.5 in 9/2006) Urinalysis – 1+ protein (no quantification available), no red cells or cellular casts Glucose 96 mg/dl Albumen 2.7 gm/dl ANA, UPEP, SPEP negative (Consultation Case – Carrie Phillips, MD, Indiana University)

Click for larger Figure 1: PAS stain There is severe mesangial matrix expansion with mild mesangial hypercellularity. The capillary loops are open.   Click for larger Figure 2: JMS stain Silver stain show mesangial matrix expansion by weakly argyrophillic material. Most capillary loop basement membranes are normal but there is segmental thickening and irregularity.   Click for larger Figure 3: Electron microscopy shows effacement of podocyte foot processes. The mesangial matrix is expanded and the capillary loop irregularly thickened by poorly delineated electron dense material. Note: the DIF showed a strong mesangial and capillary loop reaction for IgG, C3, kappa and lambda   Figure 4: Electron microscopy at high magnification reveals that the electron dense deposits have a fibrillary structure.       Question: What is the diagnostic finding? What diagnosis does it strongly suggest? Answer:   Diagnosis: Differential diagnosis of fibrillary or structured deposits: Amyloidosis Fibrillary glomerulopathy Immunotactoid glomerulopathy Cryoglobulinemic glomerulonephritis Lupus glomerulonephritis (fingerprint deposits) Collagofibrotic glomrulopathy Nail-patella syndrome Fibronectin glomerulopathy   Diagnosis: Fibrillary glomerulopathy (Fgn)   Discussion: Fibrillary glomerulonephritis is an uncommon immune complex-associated disorder. Immunofluorescence reveals that the fibrillar deposits contain IgG, C3, and both kappa and lambda light chains. By definition the deposits are Congo red negative and patients should have not have circulating cryoglobulins. There is considerable debate about the relationship of Fgn with a similar entity known as immunotactoid glomerulopathy (ITgn). Both disorders have organized deposits that stain for IgG, C3, kappa, and lambda and are Congo red negative. In ITgn the deposits are microtubular, have a larger diameter and are arranged in stacked arrays. Proponents that Fgn and ITgn are the same disease argue that the microtubular appearance is a function of size and EM resolution rather than an intrinsic physicochemical or clinical difference. However, several groups have noted that some patients with ITgn will have a monoclonal gammopathy or a hematologic malignancy. I will not comment further about this issue.   Patients with Fgn are characteristically adults. They present with proteinuria that may be nephrotic range and microscopic hematuria. Renal insufficiency is often present at diagnosis and most patient progress to ESRD. No effective treatment has been identified. As is typical of most immune complex gns, recurrence in a renal transplant occurs in a proportion of patients. References: Clin J Am Soc Nephrol 1:1351-1356, 2006. Kidney Int 63:1450-1461, 2003. Kidney Int 62:1764-1775, 2002.

Stephen M. Bonsib, MD  (Dr Bonsib's Bio)

Chairman Pathology

Director, Renal Pathology Consultative Services

Albert G. and Harriet G. Smith Professor of Pathology

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