This relatively benign disorder is the most frequent cause of nephrotic syndrome in children. It is characterized by diffuse loss of foot process of epithelial cells in glomeruli that appear virually normal by light microscopy. The peak incidence is between 2 and 6 years of age. The disease sometimes follows a respiratory infection or routine prophylatic immunization, Its most characteristic feature is its usually dramatic response to corticosteroid therapy.

Although the absence of immune deposits in the glomerulus excludes classic immune complex mechanisms, several features of the disease point to an immunologic basis, including (1) the clinical association with respiratory infections and prophylactic immunization; (2) the response to corticosteroid and immunosuppressive therapy; (3) the association with other atopic disorders (e.g., eczema, rhinitis); (4) the increased prevalence of certain HLA haplotypes in patients with minimal change disease associated with atopy (suggesting a possible genetic predisposition); (5) the increased incidence of minimal change disease in patients with Hodgkin disease, in whom defects in T cell-mediated immunity are well reorganized; (6) the recurrence of proteinuria after transplantation in patients with the related disorder focal segmental glomerulosclerosis. (7) reports of proteinuria- inducing factors in the plasma or lymphocyte supernatants of patients with lipoid nephrosis and focal glomerulosclerosis.

The current hypothesis is that lipoid nephrosis involves some immune dysfunction, eventually resulting in the elaboration of a cytokine like circulating substance that affects visceral epithelial cells and causes proteinuria. The ultrastructural changes point to a primary visceral epithelial cell injury and studies in animal modles suggest the loss of glomerular polyanions; thus defects in the charge barrier contribute to the proteinuria. Detachment of epithelial cells a consequence of diminished adhesion to GBM may also lead to protein loss. Recent clues might come from the discovery of mutations in a renal glomerular protein, termed nephrin, in a hereditary form of congenital nephrotic syndrome with minimal change morphology . This protein resembles immunoglobulin like cell adhesion receptors that participate in cell ? cell and cell ? matrix interactions thus supporting a role for epithelial adhesion defects in this disease.

Clinical Course

Despite massive proteinuria renal function remains good and there is commonly no hypertension or hematuria. The proteinuria usually is highly selective, most of the protein consisting of albumin. Most children (more than 90% with minimal change disease respond rapidly to corticosteroid therapy. However the nephrotic phase may recur and some patients may become steroid dependent or resistant. Neverthless the long term prognosis for patients is excellent and even steroid dependent disease resolves when children reach puberty. Although elders are slower to respond the long term prognosis is also excellent.

As noted minimal change disease in elders can be associated with Hodgkin disease and less frequently other lymphomas and leukemias. In addition secondary minimal change disease may follow NSAID therapy usually in association with acute interstitial nephritis.