Focal Segmental Glomerulosclerosis

Key Features

• A relatively common renal pattern of injury

• May result from damage to podocytes; such damage may be

  • Primary from a renal-limited disorder

  • Secondary to another underlying disease state

• Primary renal-limited disorders fall into three categories

  • Heritable abnormalities in any one of several podocyte proteins or to underlying type 4 collagen mutations

  • Polymorphisms in the APOL1 gene in patients of African ancestry

  • Increased levels of a circulating permeability factor

• Secondary causes include renal overwork injury, obesity, hypertension, chronic urinary reflux, HIV or SARS-CoV-2 infection, or analgesic or bisphosphonate exposure

Clinical Findings

• Nephrotic syndrome

• Decreased glomerular filtration rate present in 25–50% of patients

Diagnosis

• Kidney biopsy

  • Light microscopy shows sclerosis of segments of some glomeruli

  • Immunofluorescence shows IgM and C3

  • Electron microscopy shows fusion of epithelial foot processes

• Genetic testing is being done more commonly in primary cases

Treatment

• Supportive care for nephrotic patients

  • Diuretics for edema

  • Angiotensin-converting enzyme inhibitors or angiotensin receptor blockers for proteinuria and hypertension

  • Statins or niacin for hyperlipidemia

• Prednisone, 1 mg/kg/day orally for 4–16 weeks followed by a slow taper reserved for cases of nephrotic primary focal segmental glomerulosclerosis presumed to be due to a circulating permeability factor

• Patients with secondary focal segmental glomerulosclerosis do not benefit from immunosuppressive therapy; treatment should be directed at the inciting cause

• Calcineurin inhibitors (eg, cyclosporine, tacrolimus, pimecrolimus) and mycophenolate mofetil can be considered for patients with steroid-resistance

• Plasma exchange therapy, and possibly rituximab, appear to be beneficial in lowering risk of graft loss in patients just prior to kidney transplantation and in lowering risks of relapse in those exhibiting early signs of relapse