Minimal change disease - Clinical Tree

1. What are the diagnostic criteria for nephrotic syndrome?

Nephrotic syndrome is a syndrome that results from severe proteinuria. Heavy glomerular protein losses (≥3.5 g in an adult or >40 mg/m ² per hour in a child) lead to the other three criteria for nephrotic syndrome: hypoalbuminemia, hyperlipidemia, and edema. From a practical standpoint, measuring a urine total protein-to-creatinine ratio is preferable to collecting a 24-hour urine for protein. A ratio of ≥3.5 correlates with nephrotic-range proteinuria.

2. What is minimal change disease (MCD; minimal change nephrotic syndrome)?

MCD is a disorder of glomeruli that leads to heavy proteinuria. Kidney biopsy shows normal glomeruli by light microscopy but shows effacement of the podocyte foot processes on electron microscopy. Immunofluorescent microscopy typically is negative, although some patients may show staining for immunoglobulin M (IgM) in the mesangial regions of the glomeruli. Technically, a patient cannot be said to have MCD with certainty without a kidney biopsy. However, so many young children with nephrotic syndrome have MCD that kidney biopsies are performed only in children with atypical findings or after failure of a trial of glucocorticoids. Older adolescents and adults are diagnosed with MCD after a kidney biopsy is performed.

3. How likely is MCD to be the cause of nephrotic syndrome in any individual?

MCD is the cause of nephrotic syndrome in approximately 90% of children younger than age 6, in approximately 65% of older children, and in approximately 20% to 30% of adolescents. In adults with primary glomerular diseases, only 10% to 25% of nephrotic syndrome results from MCD, which puts it third after membranous nephropathy and focal, segmental glomerulosclerosis.

4. What causes MCD?

MCD is an immune-mediated disease, thought to be due to a circulating factor capable of inducing proteinuria. Presumably the circulating factor is secreted by lymphoid cells and functions as a vascular permeability factor and directly affects podocyte function. Although most cases are idiopathic, MCD, particularly in adults, may be associated with neoplastic disease such as lymphoma, toxic or allergic reactions to drugs, certain infections, allergies, or other autoimmune disorders.

5. How common is MCD?

The prevalence of MCD in children is approximately 16 per 100,000, but it is much less prevalent in adults.

6. What is the typical clinical presentation of MCD?

Patients with MCD typically present with mild to severe edema. Because the onset with periorbital edema commonly follows an upper respiratory infection in young children, nephrotic syndrome may sometimes be confused with an allergic reaction until a more thorough evaluation is performed. In the youngest children, there is a 2:1 male to female prevalence, but by adolescence and beyond males and females are equally affected. Other symptoms can include abdominal pain, diarrhea, poor appetite, and decreased urine output. Rarely, a patient may present with sepsis.

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