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Diagnosis:

IgA Nephropathy

Immunoglobulin A nephropathy (IgAN) is characterized by predominance of glomerular IgA deposits in the abscence of systemic disease. Although initially regarded as a benign disease, this glomerulopathy is now recognized as a major cause of end-stage kidney disease and chronic renal insufficiency. It is the most prevalent form of glomerulonephritis worldwide. The frequency shows geographic variation being more prevalent in Asia: (25% to 45% of kidney biopsies); the estimate frequency in North America, the United Kingdom, and northwest Europa is 5-10% of biopsies. Urine screening programs and biopsy polices can influence frequences and the spectrum of clinical manifestations reported.

Hematuria is the most consistent clinical manifestation of IgAN, and it is observed at some point during the clinical course in more than 95% of patients. Proteinuria is encountered to some degree in nearly all patients, 5-10% in nephrotic range, as in our case: 4.27 g/24h in the last control. Nearly 25-30% of patients develop end-stage renal disease over a 20-years course; approximately 1% of all patients per year reach end-stage renal disease.

Clinical findings associated with increased likelihood of progression include: older age at onset, no episodic macrohematuria, heavy proteinuria, hypertension, persistently decreased glomerular filtration rate or serum creatinine persistently increased, and impaired ability to concentrate urine. Pathologic features associated with poor prognosis include: glomerular sclerosis (global or focal), interstitial fibrosis, endocapillary proliferation, numerous crescents (more than 10%), capillary immune deposits, co-deposits of abundant IgG or IgM, and hyaline arteriolosclerosis.

There is no international consensus for the pathological classification of IgAN. A number of classifications are in use, and have their supporters. This lack of consensus is a significant disadvantage in developing systems with increasing power to predict outcome for both individuals and cohorts of patients, in making international comparisons between different outcome studies, and in refining the stratification of risk for the design of clinical intervention trials. A proposal to develop a consensus classification came forward simultaneously from the International IgA Nephropathy Network, under the auspices of Renal Pathology Society and the International Society of Nephrology [See link]

In the present case kidney function was chronically altered and it worsened during hospitalization. This acute increase of creatinine would be related to crescents, as seen in Figure 4, although only 3 of 12 glomeruli show this extracapillary proliferation.

See the chapter [Nefropatía IgA y Púrpura de Henoch-Schönlein] (only in spanish).

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Bibliography

• Barratt J, Feehally J. IgA nephropathy. J Am Soc Nephrol. 2005 Jul;16(7):2088-97. [PubMed link]
• Magistroni R, Furci L, Leonelli M, Masellis M, Ligabue G, Lucchi L, Lupo A, Brezzi B, Gambaro G, Manganelli L, Pedrazzi G, Ricardi M, Bormioli L, Albertazzi A. A validated model of disease progression in IgA nephropathy. J Nephrol. 2006 Jan-Feb;19(1):32-40. [PubMed link] [Free full text]
• Haas M. Histology and immunohistology of IgA nephropathy. J Nephrol. 2005 Nov-Dec;18(6):676-80. [PubMed link] [Free full text]
• Lai AS, Lai KN. Molecular basis of IgA nephropathy. Curr Mol Med. 2005 Aug;5(5):475-87. [PubMed link]
• Kobayashi N, Nishida M, Aoyama M, Yokoi K, Yahata T, Tatsujiro T, Sakata K, Shiraishi I, Itoi T, Hamaoka K. Rapidly progressive IgA nephropathy. Indian J Pediatr. 2005 Mar;72(3):257-60. [PubMed link] [Free full text]
• Lai KN, Chan LY, Leung JC. Mechanisms of tubulointerstitial injury in IgA nephropathy. Kidney Int Suppl. 2005 Apr;(94):S110-5. [PubMed link]
• Julian BA, Novak J. IgA nephropathy: an update. Curr Opin Nephrol Hypertens. 2004 Mar;13(2):171-9. [PubMed link]
• Barratt J, Feehally J, Smith AC. Pathogenesis of IgA nephropathy. Semin Nephrol. 2004 May;24(3):197-217. [PubMed link]

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