Minimal change disease

MCD is a glomerular disorder characterized by nephrotic syndrome and minimal histologic changes on light microscopy, with diffuse podocyte foot process effacement visible on electron microscopy. It is the most common cause of nephrotic syndrome in children and can also occur in adults.

The pathophysiology of MCD is not fully understood, but it is thought to T-cell-mediated immune dysregulation leading to the release of a circulating permeability factor. This factor causes podocyte injury and widespread effacement of foot processes, resulting in increased glomerular permeability and massive proteinuria.

MCD accounts for approximately 70-90% of nephrotic syndrome cases in children and 10-15% in adults. The incidence is higher in boys during childhood but becomes more balanced in adulthood. It may occur at any age, with peaks in early childhood and a smaller peak in late adulthood. The estimated incidence in children is 2-7 cases per 100,000.

The risk factors for MCD are primarily young age, family history of nephrotic syndrome.

Patients with MCD typically present with nephrotic syndrome, characterized by periorbital, lower extremity, and genital edema, frothy urine, and in severe cases, anasarca with ascites and pleural or pericardial effusions. Presentation may follow an upper respiratory infection and is occasionally complicated by intravascular volume depletion and oliguria. Infections such as sepsis, pneumonia, and peritonitis are common, particularly in children, due to immunoglobulin loss and impaired T-cell function. AKI is more common in adults but may occur in children, especially when accompanied by diarrhea, diuretic use, or sepsis. Gross hematuria is rare, occurring in roughly 3% of cases, but microhematuria may be seen in up to 20%. Laboratory findings include 3+/4+ proteinuria on dipstick and nephrotic-range proteinuria on quantification. Serum albumin is typically < 2 g/dL, with accompanying hypoalbuminemia, hyperlipidemia, elevated α₂-globulin, and reduced γ-globulin. Immunoglobulin profile shows decreased IgG and IgA, and elevated IgM and IgE. Hypercoagulability is common due to urinary loss of antithrombin III, hemoconcentration, thrombocytosis, and elevated fibrinogen and clotting factors, increasing the risk of venous thrombosis.

The prognosis of MCD is generally favorable, with excellent long-term kidney survival in patients who respond to corticosteroids. Most patients respond well to corticosteroids, with remission rates exceeding 90% in children and 80% in adults. However, relapses are common, especially in children, with approximately 60-70% experiencing at least one relapse. A minority develop frequent relapses or steroid dependence. Progression to CKD or end-stage kidney disease is rare, particularly in steroid-responsive cases.