Iga nephropathy N02.8

Jean Berger, 1968

Immunocomplex disease with formation of abnormal IgA1 molecules (galactosylated IgA1) and immune complex deposits in the mesangium of the renal glomerula.

Idiopathic form of IgA nephropathy

Secondary: in adults, IgA nephropathy often remains monorganically restricted to the kidney. Common in SLE, liver cirrhosis, sprue, monoclonal IgA gammopathy; also common in dermatitis herpetiformis. In systemic purpura Schönlein-Henoch, IgA nephropathy is a partial manifestation.

MEST (Oxford) classification of IgA nephropathy:

• Mesangial hypercellularity (0=<50%; 1=>50%)
• Endocapillary hypercellularity (0=no; 1=yes)
• Segmental sclerosis/adhesion (0=no; 1=yes)
• Tubulus atrophy, interstitial nephrosis (0=0-25%; 1=26-50%; 2=>50%)

The most common form of all primary glomerulonephritides worldwide (Moeller S et al. 2014). Prevalence: 100-150/100,000 inhabitants.

Triggering factors are often mucosal infections; pathogenetically, food allergens including gluten are also considered to be contributory factors. Increased immunoreactivity to gluten, possibly combined with gluten-sensitive enteropathy, has been reported.

In the pathogenesis of IgA nephropathy, variations in the integrin subunit beta 2(ITGB2) and the Fc fragment of the IgE receptor (FCER1G) play an important role (Jiang X et al. 2020).

m>f; as monoorganic nephropathy mainly in men between the age of 20 and 30 years (Thaiss F et al. 2000). The rare familial occurrence is described. As a systemic clinical picture in combination with palpable purpura, arthralgias, abdominal pain and intestinal bleeding(Purpura Schönlein-Henoch).

The leading clinical symptoms of IgA nephropathy can vary widely. It ranges from minimal findings with minor persistent microhematuria to recurrent episodes of macrohematuria. Macrohematuria is almost always associated with mucosal infection. Frequently, hematuria is accompanied by mild proteinuria (0.5 to 2.0 g/day). Less commonly (up to 10% of patients), nephrotic proteinuria (> 3 g/24 h) or rapidly progressive glomerulonephritis occurs (Thaiss F et al 2000). Mild to moderate hypertension develops in about 40% of patients.

Concomitant flank pain is characteristic. In adults, IgA nephropathy usually remains monorganic to the kidney.

In children, IgA nephropathy is often a partial symptom of Schönlein-Henoch purpura (Mani LY et al. 2015).

Complicatively, IgA nephropathy (IgAN) may be associated with psoriasis (often severe) (Garces CC et al. 2021).

Non-selective proteinuria (usually <3g/day) and glomerular haematuria (acanthocytes) in the urine sediment. Serum IgA levels increased in 40% of patients. Detection of circulating immune complexes possible in 50-70% of cases.

Clinic; kidney biopsy ("triple diagnostics" from light, immune and electron microscopic examination of the biopsy material. Detection of mesangial deposits of IgA, proliferation of mesangium cells and mesangium matrix). Prognostically unfavourable pathological-anatomical factors are: focal and segmental glomerular sclerosis, tubulointerstitial fibrosis and arterio- and arteriolosclerosis of the renal vessels. If these factors are present, the indication for therapeutic measures is given.

Other diseases with proteinurei with/without haematuria. Poststreptococcal glomerulonephritis.

In patients with a low risk (isolated microhaematouria and proteinuria <0.5g/d and normal GFR) a "wait-and-see strategy" is justified.

In patients with an intermediate risk (proteinuria 0.5g-1.0g/d and reduced GFR +/- hypertension), therapy with ACE inhibitors is recommended (Note: In multicentre studies, it has been shown that the administration of an ACE inhibitor leads to a significant reduction in the progressive loss of function (Thaiss F et al. 2000). In case of resistance to therapy, addition of prednisolone.

In patients with nephrotic syndrome or "Rasch progressive glomerulonephritis" glucocorticoids (prednisolone 1mg/kg bw) for 8 weeks combined with cyclophosphamide (500mg/m2 body surface) as "pulse therapy", otherwise symptomatic.

Alternative: In several controlled clinical trials (8 RCTs with a total of 357 patients), the use of mycophenolate mofetil produced satisfactory results superior to those obtained with cyclophosphamide. (Cheung CK et al. 2015).

Fish oil: In a prospective study the positive effect of polyunsaturated fatty acids from fish oil could be demonstrated (the eicosapentaenoic and docosahexaenoic acids contained in fish oil lead to a favourable profile of cyclooxygenases. Patients with IgA nephritis who ate 3-4 g of fish oil daily had a significantly more favourable course of their disease than patients not treated in this way.

Accompanying prophylaxis of potentially developing secondary hyperparathyroidism, vitamin D deficiency, renal anaemia and acidosis, a lipid metabolism disorder. Important: dietary guidance of patients.

Prognostic assessment using MEST criteria. The extent of proteinuria is of decisive importance. Remission is defined as 3 consecutive negative results with regard to haematuria and proteinuria (Suzuki Y et al. 2014).

Good prognosis with healing in 25% of patients. Terminal renal failure occurs in 50% of patients over 10-20 years, and nephrotic syndrome in 25%. After kidney transplantation recurrence in about 40%.

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