Minimal change disease - Glomerular disease

Minimal change disease

Definition

Minimal change disease (MCD) is an important cause of nephrotic syndrome, characteristically the glomeruli look normal on light microscopy.

Age

Causes up to 90% of cases of nephrotic syndrome in those under age of 10, but only âˆ¼20% of cases in adulthood (more often in young adults).

Sex

M > F in childhood, and M = F in adults.

Aetiology/pathophysiology

Idiopathic in almost all cases. Very rarely secondary, e.g. to drugs, malignancy. It is thought to be a T lymphocyte mediated disorder, perhaps with production of a cytokine (permeability factor) which damages the glomerular epithelial cells. There is no evidence of an immune complex process. The damage to the epithelial cells is believed to cause a reduction in the fixed negative charge on the glomerular capillary wall, which permits protein (particularly albumin) to cross into the urinary space. Resultant hypoalbuminaemia causes a reduced blood oncotic pressure and hence oedema. Acute renal failure can occur in MCD due to hypovolaemia, ischaemic tubular necrosis, renal vein thrombosis and interstitial nephritis.

Clinical features

Patients present with gradual development of swelling of eyelids, hands and feet, ascites and pleural effusions. The urine may be frothy due to proteinuria. Hypertension and haematuria are rare. Renal function is usually normal in uncomplicated cases.

Macroscopy/microscopy

Electron microscopy reveals fusion of the foot processes of the podocytes, this is diagnostic if the light microscopy is normal.

Investigations

In adults, renal biopsy is normally needed for diagnosis. In children renal biopsy is only indicated in patients with atypical features or who do not respond to treatment.

Management

The mainstay of treatment is with corticosteroids, with complete remission of proteinuria in over 90% of cases. Proteinuria may take up to 3 or 4 months to completely disappear. Relapse can occur when steroids are reduced. Cyclophosphamide, cyclosporine and other drugs have also been used to induce remission in steroidresistant cases, or to reduce the steroid dose in those who are steroiddependent.

Patients may also require anti-coagulation and penicillin prophylaxis.

Prognosis

Progression to CRF is very rare in those with true MCD. Repeat renal biopsy may demonstrate another condition such as focal segmental glomerulosclerosis in those who do not respond to treatment.