Nephrotic syndrome - Causes and Symptoms

Definition

The nephrotic syndrome consists of a set of symptoms and clinical signs caused by an alteration of the renal glomeruli. This condition involves a urinary excretion of over 3 grams of protein per day.

The proteinuria is caused, in particular, by the alterations that develop in the cells of the capillary endothelium, in the glomerular basement membrane (MBG) or in the podocytes, which normally selectively filter the plasma proteins on the basis of size and charge. The onset of such lesions provokes a clinical picture characterized by edema, hypercholesterolemia, loss of appetite, general malaise and foamy urine due to high protein concentrations. Fluid retention can cause dyspnea (secondary to pleural effusion or laryngeal edema), arthralgia and abdominal pain (due to ascites or, in children, mesenteric edema). Other signs and symptoms are attributable to the multiple complications that this condition entails.

The nephrotic syndrome can be primitive (due to a glomerular disease) or secondary to a pathological condition that does not exclusively affect the kidneys.

The most frequent causes of the primitive form are glomerulopathy with minimal lesions, focal segmental glomerulosclerosis and membranous nephropathy.

In most cases, secondary forms result from diabetic nephropathy and pre-eclampsia, but can also be associated with various metabolic, immunological, genetic, infectious, drug-related or neoplastic disorders.

From a physiological point of view, the nephrotic syndrome may depend on an adaptation to the reduction of the number of nephrons, pathological obesity and oligomeganefronia (a form of hypoplasia due to the deficient development of both kidneys). The condition may also be associated with genetic syndromes, such as hereditary nephritis (Alport syndrome), focal and segmental familial glomerulosclerosis and congenital nephrotic syndrome.

Infectious diseases that can cause nephrotic syndrome include: bacterial endocarditis, leprosy, syphilis, filariasis, helminth infections, malaria and schistosomiasis. Hepatitis B and C and HIV, Herpes zoster and Epstein-Barr virus infections can also cause this condition.

The nephrotic syndrome can also depend on amyloidosis, malignant hypertension, sarcoidosis, allergic reactions (for example, in relation to insect bites or inoculation of poison by snakes) and various tumors (including leukemia, lymphomas, melanoma, myeloma multiple and carcinoma of lung, breast, colon, stomach and kidney). Immunological disorders associated with the disorder include, however, polyarteritis nodosa, cryoglobulinemia, erythema multiforme, Sjögren's syndrome and systemic lupus erythematosus.

Finally, the nephrotic syndrome can be induced by the use of NSAIDs, penicillamine, pamidronate, lithium, interferon-alpha and heroin.