Immunotactoid glomerulopathy is a
rare disease defined by glomerular microtubular
immunoglobulin deposits. Since management and long-term outcomes remain poorly described, we retrospectively analyzed results of 27 adults from 21 departments of nephrology in France accrued over 19 years. Inclusion criteria were presence of glomerular
Congo red-negative monotypic
immunoglobulin deposits with ultrastructural microtubular organization, without evidence for cryoglobulinemic
glomerulonephritis. Baseline manifestations of this cohort included:
proteinuria (median 6.0 g/day),
nephrotic syndrome (70%), microscopic
hematuria (74%) and
hypertension (56%) with a median serum
creatinine of 1.5 mg/dL. Nineteen patients had detectable serum and/or urine
monoclonal gammopathy. A bone marrow and/or peripheral blood clonal disorder was identified in 18 cases (16 lymphocytic and 2 plasmacytic disorders). Hematologic diagnosis was chronic/
small lymphocytic lymphoma in 13, and
monoclonal gammopathy of renal significance in 14 cases. Kidney biopsy showed atypical membranous in 16 or
membranoproliferative glomerulonephritis in 11 cases, with microtubular monotypic
IgG deposits (kappa in 17 of 27 cases), most commonly
IgG1. Identical intracytoplasmic microtubules were observed in clonal lymphocytes from 5 of 10 tested patients. Among 21 patients who received
alkylating agents,
rituximab-based or
bortezomib-based
chemotherapy, 18 achieved a kidney response. After a median follow-up of 40 months, 16 patients had sustained kidney response, 7 had reached
end-stage kidney disease, and 6 died. Chronic/
small lymphocytic lymphoma appears as a common underlying condition in immunotactoid glomerulopathy, but clonal detection remains inconstant with routine techniques in patients with
monoclonal gammopathy of renal significance. Thus, early diagnosis and hematological response after clone-targeted
chemotherapy was associated with favorable outcomes. Hence, thorough pathologic and hematologic workup is key to the management of immunotactoid glomerulopathy.