IgM Nephropathy 11/29/2011 Jun‐Ki Park
• First described by Cohen, Border et al. in 1978, in a series of 12 cases whose initial native renal biopsy specimens displayed: ‐ mild glomerular mesangial hypercellularity on light microscopy ‐ Diffuse granular mesangial IgM and C3 deposition on IF ‐ EM showed generalized foot‐process effacement; mesangial electron‐ dense deposits were seen in ~50% of the patients. • Excluded those that showed focal sclerosis, those with systemic disease such as lupus or vasculitis. • Critical distinction between IgM mesangial nephropathy and MCD is poor response rate to steroid therapy.
Light microscopy usually indicates diffuse proliferation of mesangial cells and accumulation of extracellular mesangial matrix
Diffuse, granular, mesangial deposition of IgM, often is associated with complement, especially C3
EM shows generalized foot‐process effacement and mesangial electron‐dense deposits
• Failure to identify IgM nephropathy as a distinct clinicopathological entity thus far may have resulted from failure to adhere to strict pathological criteria. • Other series of patients with ‘IgM nephropathy’ have included patients with FSGS (O’Donoghue et al. QJM 1991) and normal glomeruli by light microscopy (Myllymaeki et al. AJKD 2003) on initial biopsy. • Its extreme forms resemble MCD and FSGS
Is IgM Nephropathy a distinct disease entity? Pro…
Border et al. KI 1988
Is IgM Nephropathy a distinct disease entity? Pro…
Border et al. KI 1988
Is IgM Nephropathy a distinct disease entity? Pro… • Recurrent IgM nephropathy in renal allograft. ‐ Solomon et al. 1981: recurrence in 3 weeks after Tx ‐ Myllymaeki et al. 2003: included normal glomeruli by light microscopy ‐ Salmon et al. NDT 2004: Recurrent diffuse, granular mesangial deposition, with increased mesangial matrix and cellularity in the allograft, 4 yrs after Tx.
Is IgM Nephropathy a distinct disease entity? Contra… • Many investigators report its presence in the context of MCD, MH and FSGS, rather than as a distinct pathological entity (Vilches et al Lab Invest 1982; Ji‐Yun et al. KI 1984; Pardo et al. AJKD 1984; Lool et al. Pathology 1985..) • Other cases show IgM on IF (often segmental rather than diffuse) but no mesangial deposits on electron microscopy. • IgM deposition without accompanying glomerular abnormalities by light microscopy is reported to occur in up to 60% or normal kidneys donated for Tx. (Bloom et al. KI 1978) • The International Study of Kidney Disease in Children (ISKDC) did not differentiate MCD with IgM+ IF from MCD when it characterized childhood nephrotic syndrome.
Is IgM Nephropathy a distinct disease entity? Contra… • Relationship of the IgM in areas of sclerosis to that in the mesangium of non‐sclerotic glomeruli is unknown, sclerotic lesions of many diseases demonstrate the presence of IgM and C3. (Velosa etal. Mayo Clin Proc 1975)
• In this setting, the IgM may be nonspecifically deposited onto an abnormally permeable glomerular basement membrane or trapped in an area of glomerulosclerosis.
Is IgM Nephropathy a distinct disease entity? Contra… • Experimental studies have demonstrated an increase in uptake of macromolecules by the mesangium in experimentally induced nephrotic syndrome whether induced by aminonucleoside of puromycin or anti‐GBM antibody. • The mechanism of increased uptake is not clear but may reflect increased mesangial perfusion in nephrotic states. It is possible that the deposition of IgM in the mesangium in INS reflects a similar mechanism Michael et al. KI 1980
Morphologic transition observed The morphologic group and outcome in patients with idiopathic nephrotic syndrome who had more than one biopsy; the presence (+) or absence (—) of IgM in the glomerulus is indicated.
Ji‐Yun et al. KI 1984
IgMN: clinical picture and long‐term prognosis • Of 2217 biopsy specimens between 1977 – 1998, 110 specimen met criteria for IgM nephropathy. (included normal glomeruli on LM) • Excluded patients with systemic disease (SLE, RA, DM, paraproteinemia) • 63 M/47F • Mean age was 29yrs (range 1‐75yrs); 36 were younger than 16yrs Myllymaeki et al. AJKD Feb 2003
IgMN: clinical picture and long‐term prognosis
Myllymaeki et al. AJKD Feb 2003
Myllymaeki et al. AJKD Feb 2003
Myllymaeki et al. AJKD Feb 2003
Myllymaeki et al. AJKD Feb 2003
Fig 2. Renal insufficiency and ESRD in patients with IgM nephropathy at time of biopsy and in postbiopsy follow‐up. Myllymaeki et al. AJKD Feb 2003
Myllymaeki et al. AJKD Feb 2003
• The histologic and clinical criteria for diagnosing IgMN, the effect of mesangial IgM on prognosis and response to therapy, and the relation of IgMN to MCD are questions that cannot be fully resolved until the genesis of the IgM deposits is understood.
Pathogenesis • The pathogenesis of IgM nephropathy remains unclear, although abnormal T‐cell function or a disturbance in immunoaggregate clearance by mesangial cells have been suggested. • Many studies have reported increased serum IgM or IgM immunocomplex concentration in patients with IgM nephropathy.
In vitro B‐lymphocyte switch disturbance from IgM into IgG in IgMN
Lin et al. Pediatr Nephrol 1989
In vitro B‐lymphocyte switch disturbance from IgM into IgG in IgMN
Lin et al. Pediatr Nephrol 1989
Fig. 1. Serum IgM levels in patients with IgM mesangial nephropathy (●), minimal change nephrotic syndrome (MCNS) with hypercellularity (◌) and MCNS with normal cellularity (□) during the acute nephrotic phase. The solid lines indicate values (mean + 2SD) from normal controls
Lin et al. Pediatr Nephrol 1989
Fig. 2. Relationship between serum IgM level and in vitro IgM production during acute nephrotic phase in patients with IgMN (●), MCNS with hypercellularity (◌) and normal cellularity (□) Lin et al. Pediatr Nephrol 1989
suppressor T‐cells
activated suppressor T‐cells suppressor T‐cell inducers
Lin et al. Pediatr Nephrol 1989
In vitro B‐lymphocyte switch disturbance from IgM into IgG in IgMN Authors conclude: •Previous B‐lymphocyte development study demonstrated T‐cell involvement in the constant region of heavy chain (CH) isotype "switching". •The abnormality of T‐cells may influence the isotype expression and even the Ig production. •Hyperfunction of the suppressor T‐cells in the IgMN and MCNS patients with hypercellularity may play a role as a direct or indirect "switch blocker" and cause a high level of IgM production, a low level of IgG production, in these patients during the acute nephrotic phase. •The OKT8 cell levels were correlated both with in vitro IgM production and with in vitro IL‐2 production. These results indicate that high Tac expressed, activated suppressor T‐cells either directly cause hyperfunction of suppressor T‐cells or secrete some factor(s) which block(s) the switch of immunoglobulin synthesis from IgM to IgG, leading to high serum IgM and low serum IgG levels.
Circulating heavy IgM in IgMN
DiSciullo et al. Clin. Exp. Immunol 1988
Presence of heavy IgM
DiSciullo et al. Clin. Exp. Immunol 1988
Circulating heavy IgM in IgMN
DiSciullo et al. Clin. Exp. Immunol 1988
Presence of IgM‐C3 complex • Fractions were collected and assayed for the presence of IgM and IgM‐C3 complexes using enzyme immunoessays. • Dissociation of this heavy IgM by KSCN and glycine HCL is compatible with the hypothesis that the IgM is in the form of circulating immune complexes. This is further supported by the observation of acid dissociable C3‐IgM complexes.
Presence of IgM‐C3 complex • May indicate abnormality in B cell differentiation d/t defect in regulatory T cell function. • May be secondary reduce clearance of circulating antigen IgM antibody complexes. (e.g in liver dysfunction) • Circulating IgM complexes have been detected in SLE, viral hepatitis A and , IgAN, HSP, membranous GN and lupus nephritis. • Increased IgM immuncomplexes may be compatible with IgMN but not proof that IgMN is separate disease entity.
Swartz et al. Pediatr Nephrol 2009
Swartz et al. Pediatr Nephrol 2009
Swartz et al. Pediatr Nephrol 2009
Swartz et al. Pediatr Nephrol 2009
Swartz et al. Pediatr Nephrol 2009
In conclusion: ‐IgM pos IF identified to be a marker of disease severity in children with MCD, MH and FSGS ‐Children with steroid‐dependent or steroid‐resistant nephrotic syndrome and MCD with IgM pos IF have a relatively poor prognosis and poor response to adjuvant therapy ‐Children with MCD with IgM pos IF have a tendency to respond better to cyclosporine therapy as initial adjuvant therapy when compared with cyclophosphamide. ‐A prospective study is needed to verify the findings
Summary • It remains controversial, if IgMN is a separate disease • Strict pathological criteria to define IgMN needed • Studies required to elucidate pathogenetic role of IgM deposits on molecular level • Presence of IgM deposits in MCD signifies poorer prognosis, with fewer than 50% steroid sensitivity • Prospective studies required to identify favorable adjuvant therapy
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