Minimal change disease: The most common form of the nephrotic syndrome in children aged 2 to 12 years. It is the cause of nephrotic syndrome in about 90% of children younger than 10 years, about 50% to 70% of older children, and 10% to 15% of adults.
The cause of minimal change disease 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 minimal change disease include high urine protein (proteinuria), low blood albumin (hypoalbuminemia) and high cholesterol (hypercholesterolemia). The full constellation of signs and symptoms including edema, large amounts of proteinuria, hypoalbuminemia, and hypercholesterolemia constitute the nephrotic syndrome.
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.
In adults, the disease is usually secondary; whereas, in children, minimal change disease is usually primary (the cause is not known). Factors that have been associated with the onset of nephrotic syndrome in minimal change disease are drugs such as non-steroidal anti-inflammatory agents (NSAIDs), Interferon alfa, Lithium (rarely), and Gold therapy (rarely); allergens such as pollens, house dust, insect stings, and immunizations; and malignancies especially Hodgkin's disease.
The good news is that minimal change disease rarely progresses to kidney failure and most children "outgrow" the disease by their late teens with no permanent damage to their kidneys. Adults generally respond well to therapy for primary minimal change disease as well. Adults tend to have less relapses than children. For secondary minimal change disease, treatment is aimed at the offending agents. For minimal change disease due to NSAIDs, the offending NSAID must be discontinued; patients generally will have recurrence if placed back on NSAIDs. Some patients have been treated with prednisone in addition to discontinuation of the NSAID but it is not known if this is more helpful. For patients with minimal change disease secondary to Hodgkin's disease, treatment of the Hodgkin's disease will result in remission of the minimal change disease. Minimal change disease is also known as minimal change nephrotic syndrome; nil disease; lipoid nephrosis; and idiopathic nephrotic syndrome of childhood. See also: Nephrosis.