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Diagnosis: IgM nephropathy

IgM nephropathy (IgMN) is an idiopathic clinicopathologic entity causing nephrotic syndrome and characterized by staining of the mesangium by antiserum to IgM on immunofluorescence. Glomeruli show diverse grade of mesangial hypercellularity or no changes by light microscopy. The etiology of the depositions and relation to minimal change disease (MCD) remain unknown. Some authors consider IgMN and MCD clinically indistinguishable diseases (Al-Eisa A, et al. Childhood IgM nephropathy: comparison with minimal change disease. Nephron. 1996;72(1):37-43. [PubMed link]; Maruyama M, et al. [Clinical significance of IgM deposition in the mesangium and mesangial hypercellularity in adult minimal change nephrotic syndrome]. Nippon Jinzo Gakkai Shi. 2006;48(1):14-21. [PubMed link]).

Some authors have reported frequent presence of hematuria in the clinical presentation as well as a less responsive result to therapy. However, the lesion became controversial because IgM is frequently seen in biopsies as a nonspecific finding. Confusion arose owing to variance in the definition of significant IgM deposits. Dr. Jean L. Olson (Heptinstall's Pathology of the Kidney, 6th ed., LWW, Philadelphia, 2007, p. 144) restricts the diagnosis of IgM nephropathy to "those cases with bright staining (at least two positive out of three) and with demonstrable mesangial deposits on electron microscopy". However, more recent papers continue to use the immunofluorescence criterion only. Al-Eisa et al. showed more frequent mesangial expansion, more tubular atrophy, and more frequent hypertension in children with IgM nephropathy (Al-Eisa A, et al. Childhood IgM nephropathy: comparison with minimal change disease. Nephron. 1996;72(1):37-43. [PubMed link]); however, urine protein, hematuria, and serum creatinine levels were similar, and there were no differences in relapse rates or response to therapy. Another study in 110 patients with 15 year follow-up showed that 22.7% progressed to end-stage renal disease with another 13.7% manifesting renal insufficiency; half of the patients became hypertensive (Myllymäki J, Saha H, Mustonen J, Helin H, Pasternack A. IgM nephropathy: clinical picture and long-term prognosis. Am J Kidney Dis. 2003;41(2):343-50. [PubMed link]). Other authors also had reported worse prognosis in IgM Nephropathy cmpared to MCD (Zeis PM, et al. Glomerulopathy with mesangial IgM deposits: long-term follow up of 64 children. Pediatr Int. 2001 Jun;43(3):287-92. [PubMed Link]; Alexopoulos E, et al. Adult-onset idiopathic nephrotic syndrome associated with pure diffuse mesangial hypercellularity. Nephrol Dial Transplant. 2000 Jul;15(7):981-7. [PubMed link]).

In many cases with bad outcome typical morphological characteristics of focal and segmental glomerulosclerosis can be seen.

See the chapter Minimal Change Disease, IgM Nephropathy... of our Tutorial.

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Bibliography

• Swartz SJ, Eldin KW, Hicks MJ, Feig DI. Minimal change disease with IgM+ immunofluorescence: a subtype of nephrotic syndrome. Pediatr Nephrol. 2009;24(6):1187-92. [PubMed link]
• Betjes MG, Roodnat JI. Resolution of IgM nephropathy after rituximab treatment. Am J Kidney Dis. 2009;53(6):1059-62. [PubMed link]
• Bhowmik D, Chitale A, Bulchand S. IgM nephropathy in adults: incidence and correlation with electron microscopic features. Indian J Pathol Microbiol. 2007;50(3):511-4. [PubMed link]
• Maruyama M, Toyoda M, Umezono T, Miyauchi M, Yamamoto N, Kimura M, Honma M, Nishina M, Endoh M, Sakai H, Suzuki D. [Clinical significance of IgM deposition in the mesangium and mesangial hypercellularity in adult minimal change nephrotic syndrome]. Nippon Jinzo Gakkai Shi. 2006;48(1):14-21. [PubMed link]
• Myllymäki J, Saha H, Mustonen J, Helin H, Pasternack A. IgM nephropathy: clinical picture and long-term prognosis. Am J Kidney Dis. 2003;41(2):343-50. [PubMed link]
• Zeis PM, Kavazarakis E, Nakopoulou L, Moustaki M, Messaritaki A, Zeis MP, Nicolaidou P. Glomerulopathy with mesangial IgM deposits: long-term follow up of 64 children. Pediatr Int. 2001;43(3):287-92. [PubMed Link]
• Donia AF, Sobh MA, Moustafa FE, Bakr MA, Foda MA. Clinical significance and long-term evolution of minimal change histopathologic variants and of IGM nephropathy among Egyptians. J Nephrol. 2000;13(4):275-81. [PubMed link]
• Alexopoulos E, Papagianni A, Stangou M, Pantzaki A, Papadimitriou M. Adult-onset idiopathic nephrotic syndrome associated with pure diffuse mesangial hypercellularity. Nephrol Dial Transplant. 2000;15(7):981-7. [PubMed link]
• Al-Eisa A, Carter JE, Lirenman DS, Magil AB. Childhood IgM nephropathy: comparison with minimal change disease. Nephron. 1996;72(1):37-43. [PubMed link]

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