ESSENTIALS OF DIAGNOSIS
Kidney biopsy shows no changes on light microscopy.
Characteristic foot-process effacement on electron microscopy.
Minimal change disease is the most common cause of proteinuric renal disease in children, accounting for about 80% of cases. It often remits upon treatment with a course of corticosteroids. Indeed, children with nephrotic syndrome are often treated for minimal change disease empirically without a biopsy diagnosis. Biopsy should be considered for children with nephrotic syndrome who exhibit unusual features (such as signs of other systemic illness), or who are steroid-resistant or relapse upon withdrawal of corticosteroid therapy; the latter two conditions may indicate an underlying focal and segmental glomerulosclerosis (discussed below) rather than minimal change disease. Minimal change disease is less common in adults, accounting for 20–25% of cases of primary nephrotic syndrome in those over age 40 years. This entity can be idiopathic but also occurs following viral upper respiratory infections (especially in children), in association with neoplasms such as Hodgkin disease, with drugs (lithium), and with hypersensitivity reactions (especially to NSAIDs and bee stings).
Patients present with nephrotic syndrome, which confers susceptibility to infection, tendency toward thromboembolic events, severe hyperlipidemia, and possibly protein malnutrition. Minimal change disease can cause AKI due to renal tubular damage and interstitial edema.
B. Laboratory and Histologic Findings
There is no helpful serologic testing. When kidney biopsy is performed (see considerations above), glomeruli appear normal on light microscopy and immunofluorescence (eFigure 22–12). On electron microscopy, there is a characteristic effacement of podocyte foot processes (eFigure 22–13). Mesangial cell proliferation may be seen in a subgroup of patients; this finding is associated with more hematuria and hypertension and poor response to standard corticosteroid treatment.
Minimal change glomerulonephritis. (H&E stain.) (Used, with permission, from Jean Olson, MD.)
Minimal change glomerulonephritis. (Used, with permission, from Jean Olson, MD.)
Treatment is with prednisone, 60 mg/m2/day orally; remission in steroid-responsive minimal change disease generally occurs within 4–8 weeks. Adults often require longer courses of therapy than children, requiring up to 16 weeks to achieve a response. Treatment should be continued for several weeks after complete remission of proteinuria, and dosing tapers should be individualized. A significant number of patients will relapse and require repeated corticosteroid treatment. Patients with frequent relapses or corticosteroid resistance may require cyclophosphamide, a calcineurin inhibitor (tacrolimus, cyclosporine), or rituximab to induce subsequent remissions. Progression to ESRD is rare. Complications most often arise from prolonged corticosteroid use.
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