The kidneys of people with nephrotic syndrome don't work properly, causing large amounts of protein to leak into their urine. It can affect people of any age, but is often first seen in children aged between two and five years. The loss of protein can cause a range of problems, including swelling of body tissues and a greater chance of catching infections. Heavy proteinuria, clinically manifesting as the nephrotic syndrome, is almost always due to primary renal involvement in childhood. Studies from different parts of the world (Drummond et al., 1966; Tsao, Chan, and Gibson, 1969; White, Glasgow, and Mills, 1970; Habib and Kleinknecht, 1971) have shown a fair degree of homogeneity regarding the clinicopathological picture and therapeutic response.
Symptoms can usually be controlled by medication, with steroids often used. Children with nephrotic syndrome have times when their symptoms are under control (remission), followed by times when symptoms return (relapses). Most will relapse less frequently as they get older, eventually "growing out of it" by their late teens. Most children with nephrotic syndrome respond well to steroids and aren't at risk of kidney failure. Most children with nephrotic syndrome have what doctors call "minimal change disease". This means their kidneys will appear normal or nearly normal if a tissue sample was studied under a microscope. The cause of minimal change disease is unknown.