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Fibrillary and Immunotactoid Glomerulopathies

By

Frank O'Brien

, MD, Washington University in St. Louis

Reviewed/Revised Jun 2023
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Topic Resources

Fibrillary and immunotactoid glomerulopathies are rare conditions defined pathologically by organized deposition of nonamyloid microfibrillar or microtubular structures within the renal mesangium and basement membrane.

Fibrillary and immunotactoid glomerulopathies are thought by some experts to be related disorders. They are found in about 0.6% of renal biopsy specimens, occur equally in men and women, and have been described in patients ≥ 10 years. Average age at diagnosis is about 45. Mechanism is unknown, although deposition of immunoglobulin, particularly IgG kappa and lambda light chains and complement (C3), suggests immune system dysfunction. Patients may have accompanying cancer, paraproteinemia, cryoglobulinemia, plasma cell dyscrasia, hepatitis C infection, or systemic lupus erythematous Systemic Lupus Erythematosus (SLE) Systemic lupus erythematosus is a chronic, multisystem, inflammatory disorder of autoimmune etiology, occurring predominantly in young women. Common manifestations may include arthralgias and... read more Systemic Lupus Erythematosus (SLE) , or they may have a primary renal disease without evidence of systemic disease. Immunotactoid glomerulonephritis in particular is commonly associated with chronic lymphocytic leukemia Chronic Lymphocytic Leukemia (CLL) Chronic lymphocytic leukemia (CLL) is characterized by progressive accumulation of phenotypically mature malignant B lymphocytes. Primary sites of disease include peripheral blood, bone marrow... read more and B cell lymphoma Overview of Lymphoma Lymphomas are a heterogeneous group of tumors arising in the reticuloendothelial and lymphatic systems. The major types are Hodgkin lymphoma Non-Hodgkin lymphoma See table Comparison of Hodgkin... read more .

All patients have proteinuria, > 60% in the nephrotic range. Microscopic hematuria is present in about 60%; hypertension Hypertension Hypertension is sustained elevation of resting systolic blood pressure (≥ 130 mm Hg), diastolic blood pressure (≥ 80 mm Hg), or both. Hypertension with no known cause (primary; formerly, essential... read more Hypertension , in about 70%. Slightly > 50% have renal insufficiency at presentation.

Diagnosis of Fibrillary and Immunotactoid Glomerulopathies

  • Renal biopsy

Serum C3 and C4 are usually measured and are occasionally decreased.

Light microscopy of a biopsy specimen shows mesangial expansion by amorphous eosinophilic deposits and mild mesangial hypercellularity. Various other changes may be present on light microscopy (eg, crescent formation, membranoproliferative patterns). Congo red staining is negative for amyloid. Immunostaining reveals IgG and C3 and sometimes kappa and lambda light chains in the area of the deposits.

Electron microscopy shows glomerular deposits consisting of extracellular, elongated, nonbranching microfibrils or microtubules. In fibrillary glomerulonephritis, the diameter of the microfibrils and microtubules varies from 20 to 30 nm. In immunotactoid glomerulonephritis, the diameter of the microfibrils and microtubules varies from 30 to 50 nm. In contrast, in amyloidosis, fibrils are 8 to 12 nm.

Some experts distinguish immunotactoid from fibrillary glomerulopathy by the presence of microtubular (as opposed to smaller microfibrillar) structures in the deposits; others distinguish them by the presence of a related systemic illness. For example, a lymphoproliferative disorder, monoclonal gammopathy, cryoglobulinemia, or systemic lupus erythematosus Systemic Lupus Erythematosus (SLE) Systemic lupus erythematosus is a chronic, multisystem, inflammatory disorder of autoimmune etiology, occurring predominantly in young women. Common manifestations may include arthralgias and... read more Systemic Lupus Erythematosus (SLE) may suggest immunotactoid glomerulonephritis.

Fibrillary Glomerulopathy

Treatment of Fibrillary and Immunotactoid Glomerulopathies

  • Although evidence of effectiveness is lacking, consider angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs), corticosteroids and/or other immunosuppressants

Evidence to support specific treatments is lacking although ACE inhibitors and ARBs may be used to reduce proteinuria. Immunosuppressants have been used based on anecdotal evidence but are not a mainstay of therapy; success may be greater with corticosteroids when serum complement is decreased. The disorder may recur after transplantation.

Prognosis for Fibrillary and Immunotactoid Glomerulopathies

Drugs Mentioned In This Article

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GIAPREZA
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