Minimal change disease produces glomerulonephritis with clinical features consistent with nephrotic syndrome. It is the commonest cause of nephropathy in children, accounting for 80% of cases. In addition, minimal change disease accounts for 20% of nephropathies in adults.
Minimal change disease is one of the most common causes of nephrotic Syndrome in children and adolescents. It accounts for about 50% of cases in this age group. MCKD is rare in adults, but when it does occur, it is more likely to be seen in older adults and men.
Most cases of minimal change disease are idiopathic. It is believed that the disease is caused by an immune disorder in which the immune system mistakenly attacks the kidneys. This leads to damage to the small blood vessels in the kidneys, which results in protein leakage into the urine.
Secondary causes of minimal change disease include:
- Drugs e.g. NSAIDs, lithium
- Infections e.g. syphilis, tuberculosis
- Paraneoplastic e.g. leukaemia, lymphoma
The most common symptoms of minimal change disease are those consistent with nephrotic syndrome, including proteinuria and oedema. Symptoms and signs include:
- Frothy urine: due to hyperlipidaemia and fatty casts in urine
- ↑ Risk of thromboembolism: due to loss of antithrombin III in urine
- ↑ Risk of infection: due to loss of IgG and tissue oedema, which compromises the local blood supply and immune response)
- Generalised symptoms, including fatigue and reduced appetite
Investigations should include urine tests and blood tests as usually used when investigating nephrotic syndrome. While kidney biopsy is not usually required in children as diagnosis can be made on clinical grounds given its incidence in the paediatric population, performing a biopsy should be considered in adults. Biopsies show that the kidneys have minimal structural damage, despite the presence of protein in the urine.
Urine tests will show proteinuria and high albumin:creatinine ratio. Tests include:
- Urine dipstick
- Urine microscopy and culture
- Urine albumin:creatinine ratio
Blood tests are used to check for features of nephrotic syndrome as well as exclude other causes.
- Urea and electrolytes
- Full blood count
- C-reactive protein
- Cholesterol and triglyceride levels
- Complement levels
Light microscopy shows normal histology in minimal change disease. However, electron microscopy would show deformities of podocyte foot processes.
Corticosteroids are first-line and are effective in 80% of cases. Some patients may require additional immunosuppressive therapy, such as cyclophosphamide or cyclosporine, to achieve remission.
Minimal change disease has good prognosis in both children and adults in steroid-responsive cases.