Definition of Minimal change disease

Minimal change disease: The most common form of the nephrotic syndrome, a kidney disorder that affects the structures called glomeruli which contain small capillaries surrounded by membranes through which the blood is filtered to form urine. Called minimal change disease (MCD) because under the ordinary light microscope the kidney biopsy appears normal and only under the greater magnification of the electron microscope (EM) does the biopsy show minimal changes in the glomeruli including fusion of a portion of the epithelial layer. MCD most often affects children but occurs occasionally in adults.

The cause of MCD is not fully known but it is believed to be an immune disorder in which T cells release a cytokine that damages the epithelial foot processes of the glomeruli. This leads to a leakage of albumin by the kidney. Certain events such as a viral infection, an allergic reaction, a bee sting, or an immunization may trigger an attack of MCD.

Symptoms may include edema (swelling) around the eyes, feet and ankles, and abdomen. Laboratory hallmarks of MCD include high urine protein (proteinuria), low blood albumin (hypoalbuminemia) and high cholesterol (hypercholesterolemia). The kidney biopsy under the EM shows classic findings of minimal change disease.

The main goal of treatment is to halt the outpouring of protein from the blood into the urine. Prednisone, a corticosteroid, is commonly used to stop the proteinuria. A diuretic may be given to reduce the swelling by increasing urine output. An ACE inhibitor may also be prescribed. When protein is no longer present in the urine, the dosage of prednisone is tapered down and stopped. Some children never get sick again, but most develop swelling and protein in the urine again, usually following a viral illness. However, as long as the child continues to respond to prednisone and the urine becomes protein free, he or she has an excellent long-term outlook without kidney damage.

Children who relapse frequently may be given a second type of drug called a cytotoxic agent. The agents most frequently used are cyclophosphamide, chlorambucil, and cyclosporine. After reducing protein in the urine with prednisone, the doctor may prescribe the cytotoxic agent. Treatment with cyclophosphamide and chlorambucil usually lasts for 8 to 12 weeks, while treatment with cyclosporine frequently takes longer.

The good news is that MCD rarely progresses to kidney failure and most children "outgrow" the disease by their late teens with no permanent damage to their kidneys. Also known as minimal change nephrotic syndrome; nil disease; lipoid nephrosis; and idiopathic nephrotic syndrome of childhood. See also: Nephrosis.

Common Misspellings: minimal change diease, minimal change desease