Which condition is characterized by minimal change in light microscopy and is the most common cause of nephrotic syndrome in children?

Minimal change disease is characterized by the presence of minimal morphological changes in light microscopy, which is a distinguishing feature of this condition. Under a light microscope, the glomeruli appear normal, hence the term "minimal change." This is in contrast to other forms of kidney disease, where more significant structural changes may be observed.

It is the most common cause of nephrotic syndrome in children, accounting for approximately 80% of cases in this age group. The condition is particularly notable for its responsiveness to corticosteroid therapy, which can lead to a complete remission of symptoms, including proteinuria and edema.

In children with this condition, the primary abnormality occurs at the level of the podocytes, leading to changes in the glomerular filtration barrier that result in significant proteinuria. Unlike other types of nephrotic syndrome that are associated with more significant findings on microscopy, minimal change disease requires further tests, such as electron microscopy, to see the effacement of podocyte foot processes that are responsible for the protein loss.

This understanding of minimal change disease emphasizes its unique clinical and histopathological profile, making it distinct from other nephrotic syndromes which might show more pronounced findings on microscopic examination.