Immunotactoid glomerulopathy.

We present 11 patients with immunotactoid glomerulopathy, a new syndrome characterized clinically by proteinuria (11/11), microscopic hematuria (9/11) and hypertension (9/11). The patients consisted of six females and five males, aged 25 to 59 years (mean, 44.6). Proteinuria was the presenting feature and the reason for renal biopsy in all patients. The diagnosis of immunotactoid glomerulopathy was established at renal biopsy by the presence of glomerular extracellular microtubules composed of immune reactants. All the biopsies studied by immunofluorescence (10 cases) had glomerular deposits of IgG and C3. In three biopsies studied with IgG subclass specific antisera, only one patient had monoclonal immunoglobulin deposits (IgG3 kappa). In six cases the glomerular deposits were analyzed for light chains. In three the deposits contained kappa only, and three consisted of both kappa and lambda. In two cases the immune aggregates were confined to the mesangium, and in the remaining eight cases, the deposits were present in the mesangium and the glomerular basement membranes. Electron-dense deposits composed of microtubules were present in the same distribution within the glomerulus as the immune reactants. The microtubules had a uniform diameter in each biopsy, but they varied in size from case to case. They were approximately the same size in eight cases (mean, 22.3 +/- 3 [SD] nm). Three cases had much larger microtubules: 34.2 nm, 35.4 nm, and 48.9 nm in diameter. Although the 22.3-nm microtubules resembled amyloid in their appearance, glomerular distribution and random orientation in the tissue, they were more than twice the diameter of amyloid (8.9 nm), and Congo red and thioflavin T stains for amyloid were negative. Similar microtubular structures have been described in patients with cryoglobulinemia, SLE and paraproteinemia, but these diseases were excluded in our patients on clinical, serologic and in some cases histologic grounds. More important, none of our patients had clinical or histochemical evidence of amyloidosis, an entity which may be confused with immunotactoid glomerulopathy on a morphologic basis. Follow-up, from 22 to 94 months (mean, 52.6) was obtained in all 11 patients, and 2 clinical courses were noted. Six patients had progressive deterioration of renal function, with five requiring dialysis. This group had severe hypertension (4/6) and nephrotic-range proteinuria (5/6) at some point in their course. The remaining five patients with stable renal function had proteinuria of less than 2.0 g/24 hr in most cases (4/5), and none had severe hypertension. This dichotomy correlated with the distribution of immunotactoids.(ABSTRACT TRUNCATED AT 400 WORDS)